J. Virol: Continued Reassortment Of Swine Flu Viruses With Genes From pH1N1 In China

 

# 8820

 

Big changes in influenza viruses – the kind that can create a novel, and potentially pandemic producing strain – come about through antigenic shift, also known as reassortment.  For shift to occur, two different flu strains must infect the same host simultaneously, and swap one or more gene segments.

 

Most reassortant viruses are evolutionary failures, but every once in awhile a more `fit’ virus emerges.

 

While seemingly an unlikely confluence of events – for pigs - who number in the millions, live in close quarters, have frequent contact with other pigs, birds, and humans, and who are notoriously susceptible to flu – shift happens with surprising frequency.

 

Since pigs can be infected by more than one flu virus at the same time, it is possible for two viruses to swap genetic material (reassort), resulting in a new hybrid strain.

 

Here in North America we’ve been watching the evolution of several swine variant viruses (H1N1v, H1N2v, H3N2v) over the past few years, all of which have reassorted with - and picked up the M gene segment from – the 2009 H1N1 virus (see Keeping Our Eyes On The Prize Pig).

 

Although reassortant flu viruses can emerge anywhere in the world (2009 H1N1 first emerged in North America), nowhere are pigs watched with more interest than in China, where huge populations of pigs are raised with frequent contact with other species, including humans.

 

Last year, in  EID Journal: Predicting Hotspots for Influenza Virus Reassortment, we saw China ranked as one of the globe’s top breeding grounds for new flu strains. 

 

Today we’ve a new paper, appearing in the Journal of Virology, that looks at the expanding diversity of reassorted swine flu viruses carrying genes from the 2009 H1N1 pandemic virus in Chinese pigs.  While the fully `humanized’ 2009 H1N1 virus doesn’t circulate in swine, researchers have isolated at least 17 reassortants  containing pH1N1-origin genes.

 

First the link and abstract, then I’ll have a bit more.

 

 

Expansion of genotypic diversity and establishment of 2009 H1N1 pandemic-origin internal genes in pigs in China

Huyi Lianga,b,c, Tommy Tsan-Yuk Lama,b,c, Xiaohui Fand, Xinchun Chena, Yu Zenga,c, Ji Zhoua,b,c, Lian Duana,b,c, Maying Tseb, Chung-Hei Chanb, Lifeng Lib,c, Tak-Ying Leungb, Chun-Hung Yipb, Chung-Lam Cheungb, Boping Zhoua, David K. Smithb,c, Leo Lit-Man Poona,b, Malik Peirisa,b, Yi Guana,b,c⇑ and Huachen Zhua,b,c⇑

ABSTRACT

‘Two-way' transmission of influenza viruses between humans and swine has been frequently observed and the occurrence of the 2009 H1N1 pandemic influenza (pdm/09) demonstrated that swine-origin viruses could facilitate the genesis of a pandemic strain. Although multiple introductions to and reassortment in swine of the pdm/09 virus have been repeatedly reported in both Eurasia and the Americas, its long-term impact on the development of swine influenza viruses (SIVs) has not been systematically explored. Our comprehensive evolutionary studies on the complete genomes of 387 SIVs obtained from 2009 to 2012 in influenza surveillance in China revealed 17 reassortant genotypes with pdm/09-origin genes.

Even though the entire 2009 pandemic virus and its surface genes cannot persist, its internal genes have becoming established and are now the predominant lineages in pigs in the region. The main persistent pdm/09-origin reassortant forms had at least 5 pdm/09-origin internal genes and their surface genes primarily of European avian-like (EA) or human H3N2-like SIV origin. These findings represent a marked change to the evolutionary patterns and ecosystem of SIVs in China. It is possible that the pdm/09-origin internal genes may be in the process of replacing EA- or triple reassortant-like internal genes. These alterations to the SIV gene pool need to be continually monitored to assess changes in the potential for SIVs to transmit to humans.

 

 

Remarkably, in less than five years, the swine influenza virus (SIV) gene pool in China has been dramatically re-invented with the internal genes derived from the pH1N1 virus now dominant, and continuing to expand. 

 

While their surface genes (HA & NA) remain more or less stable, the acquisition of as many as 5 internal genes from an already `humanized’  flu virus is of concern.

 

The authors write:

 

Over the survey period, these internal genes became predominant, potentially replacing those of the enzootic SIV lineages. The altered diversity of the SIV gene pool needs to be closely monitored for changes in the potential of SIVs to transmit to humans.

 

Although with the emergence of H7N9, H10N8, and H5N8 our attentions have been focused more on avian influenzas these past couple of years, in truth, a reassortant virus could emerge from practically any species susceptible to multiple flu strains (see Study: Dogs As Potential `Mixing Vessels’ For Influenza, mBio: A Mammalian Adapted H3N8 In Seals ).

 

Historically, avian and swine influenzas have a track record of producing pandemic strains, and so we tend to watch both arenas with particularly interest. 

 

For more on influenza reassortment, you may wish to revisit:

 

Viral Reassortants: Rocking The Cradle Of Influenza

Study: Novel & Variant Swine Influenzas In Korean Pigs

Seroprevalence Study: Avian Flu In Chinese Pigs

Arkansas Reports Two H1N1v Infections

 

# 7772

 

The most common swine flu viruses are H1N1, H1N2, H3N1, H3N2, and H2N3. These viruses, when they jump to humans, are called variant viruses (e.g. H3N2v, H1N2v, H1N1v).  While the public health risk posed by these variant flu viruses appears low right now, emerging flu viruses can abruptly change, and so the CDC keeps a close watch on these variant flu strains.

.

 

So far – out of nearly 370 cases reported since 2005 - most illnesses have been moderate-to-mild, few patients have required hospitalization, and only 1 death has been attributed to these variant viruses.

 

Over the past several years, H3N2v has – by far – been the most commonly reported variant strain reported in the United States, making up more than 90% of the reported cases.  This summer, we’ve seen 18 H3N2v cases reported, from Indiana, Illinois, and Michigan.  Since 2005, H1N2v is the least common (n=5), while H1N1v had accounted for 14 cases.  

Today, from the Arkansas Department of Health, we learn of two new H1N1v cases.

 

Friday, Sep 13, 2013

Swine Flu Variant in Arkansas

Little Rock -- Two people in Arkansas have been infected with a strain of influenza (flu) known as H1N1(v) after contact with swine (pigs). These cases have been confirmed by the Centers for Disease Control and Prevention (CDC).

“A few times a year an animal variant of the influenza virus is identified in humans” said Dr. Dirk Haselow, State Epidemiologist. “Viruses of this type typically cause only mild illness in those affected and, in contrast to seasonal flu, are not easily transmitted from person to person” added Haselow. ADH has carefully monitored the patient contacts for several days without evidence of any human to human spread. Both patients identified to date have recovered fully.

When an influenza virus that normally circulates in swine is detected in a person, it is called a variant influenza virus and is labeled with a ‘v’. Influenza viruses such as H1N1(v) and other related variants are not unusual in swine and can be directly transmitted from swine to people and from people to swine. When humans are in close proximity to live swine, such as in barns and livestock exhibits at fairs, movement of these viruses can occur back and forth between humans and animals.

“We are not currently aware of any additional human influenza cases caused by H1N1(v) and do not anticipate making any new public health recommendations regarding human exposure to swine. However, we will continue to assess the situation and conduct aggressive surveillance for additional influenza cases” Haselow emphasized.

Influenza has not been shown to be transmitted by eating properly handled and prepared pork or other products derived from pigs.

"ADH has been carefully following all suspected cases of influenza. We have also worked closely with our veterinary colleagues and the Arkansas Livestock and Poultry Commission to remain informed about potential infections in swine. It is because of this careful surveillance that these cases have come to our attention,” said Haselow.

Case investigations have indicated that the illnesses resulting from H1N1(v) infection have been similar to seasonal influenza. Symptoms include fever, muscle aches, decreased energy, coughing, runny nose, and sore throat. Contact your health care provider if you are experiencing flu-like symptoms and inform the doctor if you have had contact with swine.

To prevent the spread of other infections you can get from animals, the following precautions are recommended:

• Wash your hands often with soap and running water. Particularly after contact with animals. If soap and water are not available, use an alcohol-based hand rub.
• Never eat, drink or put things in your mouth in areas where animals are present, and don’t take food or drink into areas where animals are housed.
• Never take toys, pacifiers, spill-proof cups, baby bottles, strollers or similar items into areas with animals.
• Avoid close contact with animals that look or act ill.
• Children younger than 5 years, people 65 years and older, pregnant women, and people with certain chronic medical conditions (like asthma, diabetes, heart disease, weakened immune and nervous systems) are at higher risk for serious complications of infections. These people should consider avoiding exposure to pigs and other animals at petting zoos and barns during fair season.

 

 

Although it is likely (see CID Journal: Estimates Of Human Infection From H3N2v (Jul 2011-Apr 2012)) that the number of confirmed cases (this year, and in previous years) under-represents the total number of variant flu infections that occur each year - for now, the threat to the public from these swine variant viruses appears low.

 

The CDC, in a statement on June 28th of 2013, offered this assessment on H3N2v:

CDC will continue to watch this virus closely to make sure there are no changes in the epidemiology of related human infections. That means watching for any changes in the severity of illness caused by infection with this virus and any signs that the virus is becoming more adept at spreading from person-to-person. Like all influenza viruses, it’s possible that mutations could occur that would allow this virus to become more severe or to spread more easily between people.

The risk of this virus triggering a full-blown pandemic is considered relatively low, however, because serology studies have suggested that significant numbers of adults have some existing immunity against this virus. Children younger than about 10 years old, however, have little to no immunity against H3N2v virus. Given this, a more likely scenario if H3N2v were to become more transmissible among people would be localized outbreaks in pockets of the population that do not have immunity against this virus, for example, in day care or school settings.

 

Recent  blogs on Swine variant influenza include:

 

Study: Novel & Variant Swine Influenzas In Korean Pigs

CDC Updates H3N2v County & State Fair Advice

CDC HAN Advisory On H3N2v

 

For more information, you may wish to visit the CDC’s Variant (Swine Origin) Influenza Viruses in Humans webpage, or visit these related links.

 

• Key Facts about Human Infections with Variant Viruses (Swine Origin Influenza Viruses in Humans)
• Reported Infections with Variant Influenza Viruses in the United States since 2005
• Influenza A (H3N2) Variant Virus
• What People Who Raise Pigs Need To Know About Influenza (Flu)
• Reports of Human Infections with Variant Viruses

Ontario Confirms H1N1v Case

 

Credit Wikipedia

 

# 6779

 

 

While details are somewhat scant this morning, the Province of Ontario, Canada has announced that they have detected a single of case of H1N1v flu infection in a person who had contact with pigs.

 

First the press release, then I’ll return with a bit more:

 

 

Case of Influenza A H1N1 Variant Detected in Ontario

September 25, 2012 8:00 AM

Today, Dr. Arlene King, Ontario's Chief Medical Officer of Health, issued the following statement on a case of influenza A H1N1 variant detected in Ontario:

 

"An Ontario resident has been confirmed as having been infected with an H1N1 variant (H1N1v) influenza virus. An influenza virus that normally circulates in animals is referred to as a variant virus when it infects humans.

 

This adult male patient became ill after close contact with pigs. He is being treated and closely monitored in a hospital in southwestern Ontario.

 

I would like to reassure Ontarians that this variant influenza virus rarely spreads from animals to humans. Subsequent human-to-human transmission is also rare. I would also like to stress that this is not a food safety issue; the consumption of properly cooked pork continues to be safe.  Proper cooking of meats, including pork, kills all bacteria and viruses.

 

Ontarians should remember that hand washing is the single best infection prevention and control measure against respiratory illnesses such as influenza. Individuals should wash their hands often with soap and running water, or use an alcohol-based hand rub if soap and water are not available.

 

I also would like to remind Ontarians that it is important to get immunized every year with the seasonal flu vaccine when it becomes available each fall. This will protect you against seasonal influenza viruses that are expected to circulate. Everyone six months of age and older should get the seasonal flu vaccine each year.

 

The identification of this case is the result of the strength of our current surveillance system here in Ontario. It is not an unexpected occurrence and there have been a number of human infections with variant influenza viruses in the United States over the past year.

 

I would like to thank health officials in Ontario who displayed the utmost vigilance in identifying, treating and closely investigating this case. Protecting the health of Ontarians is a priority and we will continue to monitor the situation."

 

 

H1N1v is one of the `viral contenders’ I wrote about several weeks ago in An Increasingly Complex Flu Field, and until just over a year ago, was the most commonly reported variant swine flu virus detected in humans since 2005.

 

In the past twelve months, it has primarily been the H3N2v flu virus that we’ve seen jumping from pigs to humans (300+ cases).  But 2 weeks ago, we saw a single case of H1N1v was reported out of Missouri (see The Return Of H1N1v).

 

This was only the second H1N1v case reported in a year, and it was also the second time that the H1N1v virus had been found to carry the M (matrix) gene from the 2009 H1N1 pandemic virus. 

 

This M gene  has been showing up regularly in swine variant viruses (H1N1v, H1N2v, H3N2v) for more than a year. The CDC has previously stated that `This M gene may confer increased transmissibility to and among humans, compared to other variant influenza viruses.’

 

A couple of cases of H1N1v, hundreds of miles apart, while of concern  .  .  .  does not a pandemic make. 

 

But this is further evidence that these variant viruses (H1N1v, H1N2v, H3N2v) continue to evolve, and spread widely in swine, and on occasion manage to make the jump to humans.

 

The concern is that over time one of these viruses may become a more human adapted virus, and begin to spread more easily among the population.

 

So we watch reports such as this with more than a little bit of interest.

 

For more on the flu risks from swine reassortments, I  heartily recommend Helen Branswell’s terrific piece in SciAm  from late 2010 called Flu Factories.

Flu Factories

The next pandemic virus may be circulating on U.S. pig farms, but health officials are struggling to see past the front gate

By Helen Branswell  | December 27, 2010 |

 

And for some of my earlier looks at swine influenza, you may wish to revisit:

 

H3N2v: When Pigs Flu

You Say You Want An Evolution?

The (Swine) Influenza Reassortment Puzzle

PNAS: Virulence & Transmissibility Of H1N2 Influenza Virus In Ferrets

 

 

 

# 6547

 

Timing is, as they say, everything.

 

And coming on the heels the announcement 10 days ago of three human infections with a swine-origin H1N2 influenza (see Minnesota Reports Swine H1N2v Flu), a study that appears today in PNAS is certainly well timed.

 

The study, conducted at Chungbuk National University South Korea examined viruses circulating in Korean swine (H1N2 & H3N2), and found - for the most part - they were not particularly pathogenic in ferrets.

 

The exception was a triple reassortant H1N2 virus dubbed Sw/1204, that had picked up two notable mutations, and it not only transmitted efficiently, it also caused severe (even fatal) disease in the test animals.

 

The study, is called:

 

Virulence and transmissibility of H1N2 influenza virus in ferrets imply the continuing threat of triple-reassortant swine viruses

Philippe Noriel Q. Pascua, Min-Suk Song, Jun Han Lee, Yun Hee Baek, Hyeok-il Kwon, Su-Jin Park, Eun Hye Choi, Gyo-Jin Lim, Ok-Jun Lee, Si-Wook Kim, Chul-Joong Kim, Moon Hee Sung, Myung Hee Kim, Sun-Woo Yoon, Elena A. Govorkova, Richard J. Webby, Robert G. Webster, and Young-Ki Choi

 

Ed Yong, writing for Nature has the details  on this paper:

 

Need for flu surveillance reiterated

Study of Korean pigs finds virus with pandemic potential.

Ed Yong 10 September 2012

 

 

One to the two mutations discussed in this paper is hemagglutinin (HA) (Asp-225-Gly) – also known as D225G – which is something we’ve looked at a number of times in the past.

 

This mutation involves a single amino acid change in the HA gene at position 225 (H3 numbering) from aspartic acid (D) or Asp to glycine (G), and was first linked to more severe pandemic flu by Norwegian Scientists in 2009.

 

The evidence for the D222G/N  amino acid substitution driving increased virulence, and deep lung infection, has been mixed, however. A few earlier blogs include:

 

Eurosurveillance: Debating The D222G/N Mutation In H1N1

Study: Receptor Binding Changes With H1N1 D222G Mutation

WER Review: D222G Mutation In H1N1

 

The second mutation, called NA-315 (serine to asparagine the in neuraminidase) isn’t as well studied, but is believed to assist the virus in breaking out of infected cells after replicating.

 

As Ed Yong mentions in his article - viruses often have multiple amino acid changes – and we are really just beginning to understand the ramifications of these different genetic combinations. 

 

Whether this particular virus ever ends up posing a public health threat is impossible to say, but it does illustrate these swine reassortant viruses aren’t always mild in mammals.

 

New strains of influenza come about from reassortment; the swapping of genetic material between two different flu strains in a common host. We tend to focus on swine, simply because they are highly susceptible to a variety of influenza viruses, and have a history of producing reassorted viruses.  

 

 

The pandemic virus that emerged in the spring of 2009 was the end product of several influenza strains that had kicked around the world’s swine population for many years, trading bits of genetic material back and forth, until they produced a version capable of jumping to humans.

 

But any host (human, swine, avian, or other mammal) could produce a reassorted virus.

 

For more on the flu risks from swine reassortments, I continue to heartily recommend Helen Branswell’s terrific piece in SciAm  from late 2010 called Flu Factories.

Flu Factories

The next pandemic virus may be circulating on U.S. pig farms, but health officials are struggling to see past the front gate

By Helen Branswell  | December 27, 2010 |

 

And for some of my earlier looks at swine influenza, you may wish to revisit:

 

H3N2v: When Pigs Flu

You Say You Want An Evolution?

The (Swine) Influenza Reassortment Puzzle

An Increasingly Complex Flu Field

 

(Click to enlarge)

 

# 6534

 

 

Up until 1977  it was considered normal that only one strain of influenza A circulated at a time.

 

When a new pandemic strain appeared (as it did in 1918, 1957, and 1968), the existing seasonal strain – for reasons that weren’t well understood – would vanish, and in time the new pandemic virus would settle in as the seasonal flu.

 

But in 1977 something unprecedented happened.

 

The H1N1 flu virus – which had been replaced by the pandemic H2N2 virus in 1957 (only to be replaced by the H3N2 strain 11 years later) - suddenly reappeared after 20 years absence.

 

The theory is that it escaped from a Russian or Chinese lab’s freezer, as it was almost unchanged from a strain not seen since the early 1950s. 

 

It was dubbed the `Russian flu’, and for a while, slammed Emergency rooms and Flu wards in a big way.

 

Most adults had some immunity left over from their exposures before 1957, and so kids under 20 were the hardest hit.  But unlike in 1918, 1957, and 1968 – this new flu didn’t depose the old flu.

 

Instead we ended up with two major Influenza A strains bumping shoulders and jockeying for position.  Some years H3N2 would dominate, and other years it would be H1N1.

 

Further complicating matters we also have Influenza B viruses, which while generally regarded as less serious than influenza A, have divided into two distinct lineages (Yamagata & Victoria.

 

And they too compete each year for dominance.

 

Which leaves us with (currently) four major flu strains to contend with; 

• A/H1N109
• A/H3N2
• B/Victoria
• B/Yamagata

 

These viruses constantly change and evolve over time, and we often have several clades of each strain at any given time. The most recent ECDC: Influenza Virus Characterization found 5 genetically distinct H3N2 strains in circulation across Europe.

 

The recent emergence of a new – antigenically different – H3N2 strain, along with the recent dominance of the Yamagata influenza B virus, has prompted a major change in this year’s flu vaccine.

 

• The H1N1 component remains essentially unchanged, with the A/California/7/2009 (H1N1)pdm09-like  still recommended.
• But the old A/Perth/16/2009 (H3N2)-like virus now gives way to the A/Victoria/361/2011 (H3N2)-like virus.
• And the Victoria lineage B/Brisbane/60/2008-like virus will be replaced by a Yamagata strain; the B/Wisconsin/1/2010-like virus. 

 

Which makes getting the flu vaccine this fall doubly important, as it is likely that community immunity to both of these strains is low.

 

Beyond these four, keeping researchers up late at night is the fact that there are no fewer than six influenza viruses that – while not well adapted to humans  – keep trying to nudge their way into the human host pool.

 

Most people by now are aware of the concerns over the H5N1 `bird flu’, but less well known are the H7 avian strains, which have managed to jump to humans several times over the past decade.

 

• In 2003 an outbreak of H7N7 at a poultry farm in the Netherlands went on to infect at least 89 people. Most of the victims were only mildly affected, but one person died.
• In 2004 two people in British Columbia tested positive for H7N3 (see Health Canada Report) during an outbreak that resulted in the culling of 19 million birds.
• In 2006 and 2007 there were a small number of human infections in Great Britain caused by H7N3 (n=1)  and H7N2 (n=4), again producing mild symptoms.

 

H9N2 is another avian strain that has, on rare occasions, infected humans and is believed to have some pandemic potential. Over the past dozen years a small handful of cases have been identified – mostly in Hong Kong (see CIDRAP Avian Influenza (Bird Flu): Implications for Human Disease).

 

• In January of 2010, in H9N2: The Other Bird Flu Threat, I wrote about the World Health Organization  recommending the creation of a candidate vaccine virus for H9N2.

• And in November 2010, in Study: The Continuing Evolution Of Avian H9N2, we looked at computer modeling that suggested that the H9N2 virus moving towards becoming more `human-adapted’.

 

And since 2005 the CDC has been reporting a growing number of swine flu variants that have managed – on rare occasions – to jump to humans.

 

The three main flu strains circulating in pigs are:

• H1N1
• H1N2
• H3N2

When one of these swine viruses jumps to a human host, it is then called a `variant’ virus. 

 

Up until last year, it was the trH1N1 swine virus (now called H1N1v) that had been most commonly reported. The numbers were very low – rarely more than 2 or 3 infections each year.

 

Over the past year, the focus has shifted to the H3N2v virus, which emerged in the summer of 2011. After a quiet winter and spring, this summer it has infected several hundred people in the Midwest – most (but not all) appear to have contracted it directly from exposure to pigs.

 

And as an added surprise, on Friday of last week we learned of 1 confirmed and 2 suspected cases of a variant flu strain that had only been reported twice during the previous 7 years, in Minnesota Reports Swine H1N2v Flu.

 

Next week this chart will likely need updating.

 

There are other flu strains out there, of course.

 

Earlier this year, concerns were raised over an H3N8 flu virus that had killed seals off the coast of New England, and which conceivably could infect other mammals as well (see mBio: A Mammalian Adapted H3N8 In Seals).

 

And given the propensity for flu viruses to reassort (swap gene segments), the possibility of seeing an entirely new flu strain emerge can’t be ignored.

 

Nature’s laboratory is open 24/7, and unlike human researchers suffers neither from bureaucratic rules or budgetary constraints.

 

That said, history has shown that pandemic events only happen rarely; just three times during the last century (albeit with a couple of close-but-no-cigar events thrown in to keep us on our toes). 

 

Even with all of these potential threats on the viral horizon we could easily see average flu season.

 

So far, none of these novel viruses has demonstrated the ability to transmit among humans in a sustained and efficient manner while producing significant illness.

And if we get lucky, they never will. 

 

But as schools open, and cooler weather arrives, the conditions conducive for the spread of influenza improve. And that holds true whether we are talking seasonal flu, or one of these upstart strains.

 

Today is day three of National Preparedness Month, and while most people think of emergency preparedness as something you do for hurricanes and earthquakes, flu epidemics are also worth planning for as well.

 

Preparedness should include practicing good flu hygiene (hand washing-sanitizing, covering cough & sneezes, staying home if sick) all year round, and getting the flu shot early each year.

 

No one can predict with certainty the kind of flu year we will see, and I certainly have no special insight into the matter. The CDC states it pretty succinctly:

 

What sort of flu season is expected this year?

Flu seasons are unpredictable. The CDC and WHO closely monitor flu cases to identify new viruses or potential epidemics or pandemics.

 

The CDC and the WHO obviously take pandemics and epidemics very seriously, which is reason enough for us to take a more in-depth look at pandemic preparedness later this month as National Preparedness Month continues.

Minnesota Reports Swine H1N2v Flu

 

 

# 6530

 

File this under - `Once you start looking, no telling what you’ll find’.

 

Enhanced surveillance for H3N2v flu cases associated with contact with pigs by Minnesota’s Department of Health has turned up 1 confirmed, and 2 probable human cases of H1N2v influenza.

 

The H1N2 virus is one of three flu strains that commonly circulate in swine (H1N1, H3N2, & H1N2).

 

H1N2 is assumed to be a reassortment between the H1N1 and H3N2 virus. It has on rare occasions been detected in humans. 

 

Credit CDC

 

Minnesota reported a human infection with A/H1N2 in December of 2011, and it was said to be similar to an H1N1 virus (A/New Caledonia /20/99-like) that circulated as recently as 2007. 

 

Michigan reported an H1N2 human infection in 2007. 

 

As has been pointed out in this blog before, we honestly don’t know how often these novel swine (or avian)origin flu viruses jump to humans. Given the limits of testing and surveillance, it is probably more common than the numbers suggest.

 

Heightened surveillance around the country for the H3N2v virus may very well tell us a good deal about other variant viruses that we know can occasionally show up in the human population.

 

 

Here is the Press release from the MDH.

 

 

News Release
August 31, 2012
 

Three human cases of influenza linked to swine exposure at State Fair

Strain is different from the one that prompted current surveillance and prevention efforts

Three people are believed to have developed a strain of influenza known as variant H1N2 (H1N2v) after exhibiting pigs or spending time in the swine barn at the Minnesota State Fair.

 

One of the three cases has been confirmed by CDC. Test results for the other two are pending.

 

The H1N2v strain is different from the H3N2v strain that has prompted stepped up surveillance and prevention efforts nationwide, after causing 289 reported cases of illness and one death since the beginning of the year.

 

Officials at the Minnesota Department of Health (MDH) say they are not currently aware of any additional human influenza cases caused by H1N2v, and they do not anticipate changing their current public health recommendations regarding human exposure to swine.

 

They emphasized, however, that they will continue to assess the situation and conduct aggressive surveillance for additional influenza cases.

 

Current recommendations include asking individuals at high risk for severe influenza to avoid swine contact at exhibitions, fairs, live markets and other venues, including the swine barn at the State Fair. High risk individuals include children under five years of age, pregnant women, people 65 years of age or older and those with chronic medical conditions.

 

"For the past two weeks, we have been looking very hard for cases of influenza in people who have been exposed to swine," said Richard Danila, Deputy State Epidemiologist. "We have also worked closely with our veterinary colleagues to remain informed about potential infections in swine at the Fair. It is because of this careful surveillance that these cases have come to our attention.

 

"Right now, we don’t have any basis for changing our recommendations to the public," Danila said.

 

The illness has been confirmed in a teenage girl who was exhibiting pigs at the fair and became ill on Aug. 26. The other two cases occurred in an elementary-school-aged boy who became ill on Aug. 27 after spending all day in the swine barn on Aug. 24, and a woman in her late seventies who became ill on Aug. 26 after spending a prolonged period of time in the swine barn and at the swine show in the Exhibit Hall on Aug 24.

 

Both the boy and the older woman had underlying health conditions, and were treated with antiviral drugs. The woman was hospitalized, but has now been released. All three patients have recovered or are recovering.

 

The teenager was tested for influenza after she reported illness to nursing staff at the Fair. The other cases were reported to MDH by health care providers. Health care providers have been asked to report cases of influenza-like illness in people who report that they have had contact with swine. Swine exhibitors have been asked to report it if they experience symptoms of influenza.

 

Fair officials have also been monitoring swine for possible symptoms of illness, so they can be tested. Two pigs at the swine exhibit were found to be infected with the same H1N2 virus earlier this week, and were both isolated from contact with other pigs. Infection with H1N2 is not considered unusual in pigs.

-MDH-

 

 

For more on the H1N2 virus, you may wish to revisit:

Hong Kong Swine Influenza Surveillance

CDC: Variant Influenza Strains

CDC Confirms 2 More Novel Flu Infections

If You’ve Seen One Triple Reassortant Swine Flu Virus . . .

CDC: Updated H3N2v Surveillance & Testing Guidance

 

Photo Credit CDC

 

# 6508

 

Nearly all of the recent cases of H3N2v infection in the Midwest have thus far been associated with exposure to pigs at state and county fairs. Admittedly, testing for the virus has been concentrated mostly among those with known recent swine contacts, and that may entail some bias.

 

It’s a logical place to start looking, given the swine-origin of the virus. But it’s a surveillance strategy that has the potential to miss other cases in the community.

 

Yesterday, in an attempt to cast a wider surveillance net, the CDC updated their guidance recommendations to state and local health departments on testing for the H3N2v virus.  

 

 

Interim Guidance for Enhanced Influenza Surveillance: Additional Specimen Collection for Detection of Influenza A (H3N2) Variant Virus Infections

Posted August 20, 2012

Summary

This document is an update to interim enhanced surveillance guidance first posted in December 2011. In light of the increasing numbers of cases of H3N2 variant virus (H3N2v) and increasing numbers of states reporting H3N2v cases, states should consider expanding surveillance to include rRT-PCR testing of specimens from ILINet providers statewide, and of specimens collected from people with unusual or severe presentations of ILI. States should also consider collection of specimens from outbreaks of ILI among children in child-care and school settings, since these settings have been associated with person-to-person H3N2v virus transmission in 2011. CDC will continue to evaluate new information as it becomes available and will update this guidance as needed.

<SNIP>

CDC would like state and local health departments to consider the following recommendations for influenza surveillance and testing.

1. All state public health laboratories should use the CDC Human Influenza Real-Time rRT-PCR FLU Diagnostic Panel to screen specimens for InfA, InfB, and RP.
2. Test all InfA-positive specimens with the CDC Influenza A Subtyping kit using all primer/probe sets: H1, H3, pdmInfA and pdmH1. Detailed guidance for testing can be found in the influenza surveillance diagnostic testing algorithm disseminated recently by Association of Public Health Laboratories  [27 KB, 1 page]. Specimens that are presumptive positive for H3N2v virus should be sent to CDC Influenza Division for additional testing as soon as possible.
3. Conduct contact tracing of confirmed and probable influenza A (H3N2)v cases to gather more information about the epidemiology of the virus and modes of transmission. Contact tracing is essential to evaluate potential person-to-person transmission.
4. Currently, while seasonal influenza viruses are circulating at low levels, CDC recommends increasing collection of specimens from patients with influenza-like-illness (ILI), and having these specimens sent to the state or local laboratory for rRT-PCR testing. States should specifically consider increasing collection of specimens across the state from patients presenting with ILI in the following high priority areas:
1. All ILINet providers statewide.
2. ILI outbreaks statewide, particularly among children in child care and school settings, since these settings were associated with person-to-person influenza A (H3N2)v virus transmission in 2011.
3. Unusual or severe presentations of ILI statewide, including hospitalized persons.
4. Medically attended ILI and acute respiratory infection (ARI), especially in children in counties or states where confirmed H3N2v cases have occurred.

 

With schools across the Midwest beginning their fall session this month, and scores of county and state fairs scheduled over the next couple of months, the need to pin down how this virus behaves – and whether any human-to-human transmission is occurring – increases.

 

Meanwhile, the debate over whether pigs should be excluded from public venues continues, as illustrated by this story that appeared last night on CIDRAP News, written by Lisa Schnirring.  

 

 

H3N2v infections spark debate about barring pigs from fairs

Lisa Schnirring Staff Writer

Aug 21, 2012 (CIDRAP News) – The type of flu transmission occurring mainly in young people directly exposed to pigs at fairs this summer is unprecedented, and health officials should consider keeping pigs away from the events, according to one infectious disease expert who has gone on record with his concerns.

 

As Minnesota announced its first confirmed and suspected variant H3N2 (H3N2v) infections yesterday, just a few days before the start of its state fair, local and national media outlets such as the Canadian Press aired concerns from Michael Osterholm, PhD, MPH, director of the University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP), publisher of CIDRAP News, who said that fair organizers should bar swine from fairs this year.

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Minnesota Reports First H3N2v Case

 

 

# 6503

 

Today Minnesota announced that they have joined the short list of states reporting H3N2v flu infections that have predominately been associated with exposure to pigs at county fairs. 

 

This brings to 10 the number or states reporting cases since July 12th, 2012.

 

Thus far, nearly all of the cases reported have had had direct contract with pigs or their environment, and the CDC has not found sustained and efficient transmission among humans.

 

The concern, of course, is that over time this virus might evolve to a more human-adapted virus. So public health officials track these outbreaks with considerable interest.

 

 

Today’s announcement from the Minnesota Health Department follows:

 

News Release
August 20, 2012
Minnesota Department of Health - Minnesota Department of Agriculture - Minnesota Board of Animal Health

First cases of new influenza strain reported in Minnesota

Minnesota has recorded its first confirmed case and a second probable case of a new influenza strain that people acquire through contact with pigs.

 

The two cases were reported in a pre-school-age child and an older sibling from a family living in the Twin Cities metro area. Both children developed symptoms of the illness two days after the family visited a live animal market in Dakota County on Aug. 10. Neither child required hospitalization, and both are recovering.

 

Both children were tested for the virus that causes the new flu strain, but only the younger child tested positive. However, the older child is considered a “probable” case, based on the child’s history of flu-like illness and the family connection to the younger child.

 

Officials at the Minnesota Department of Health (MDH) believe both children were most likely exposed to the new flu strain from pigs while they were at the animal market.

 

People usually get the new strain of flu – known as variant H3N2 (H3N2v) - from pigs rather than other people. A few cases have been reported where an individual got the illness from another person, but there was no further spread of the illness to additional people.

 

In addition to the Minnesota case, over 200 cases of the illness have been reported in eight states since the beginning of the year. Most have occurred in children who were exhibiting pigs at state or county fairs, or people who visited swine exhibits at fairs.

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In a related story, the CDC updated their webpage on preventing the transmission of the H3N2v virus late this afternoon as well.

 

 

Take Action to Prevent the Spread of Flu Between People and Pigs at Fairs

Pigs have their own influenza viruses (called swine influenza) that are usually different from human flu viruses. While rare, influenza can spread from pigs to people and from people to pigs. When people get swine flu viruses, it’s usually after contact with pigs. This has happened in different settings, including fairs. Right now, the Centers for Disease Control and Prevention (CDC) is concerned about a new flu virus that has been found in U.S. pigs and that has infected people too. This virus – called H3N2v – may spread more easily to humans from pigs than is usual for swine flu viruses.

There are ways to reduce the spread of influenza viruses between pigs and people.

CDC Recommendations For People At High Risk:

• If you are at high risk of serious flu complications and are going to a fair where pigs will be present, avoid pigs and swine barns at the fair this year. This includes children younger than 5 years, people 65 years and older, pregnant women, and people with certain long-term health conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions).

CDC Recommendations for People Not at High Risk:

• Don’t take food or drink or eat, drink or put anything in your mouth in pig areas.
• Don’t take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.
• Wash your hands often with soap and running water before and after exposure to pigs. If soap and water are not available, use an alcohol-based hand rub.
• Avoid close contact with pigs that look or act ill.
• Take protective measures if you must come in contact with pigs that are known or suspected to be sick. This includes wearing protective clothing, gloves, masks that cover your mouth and nose, and other personal protective equipment.
• Watch your pig (if you have one) for signs of illness and call a veterinarian if you suspect it might be sick.
• Avoid contact with pigs if you have flu-like symptoms. Wait 7 days after your illness started or until you have been without fever for 24 hours without the use of fever-reducing medications, whichever is longer. If you must have contact with pigs while you are sick, take the protective actions listed above.

A seasonal flu vaccine will not protect against H3N2v, but influenza antiviral drugs that can treat H3N2v as well as seasonal flu illness in people. These are prescription drugs. Early treatment is better, so see your health care provider as soon as you get sick if you have been exposed to pigs and get flu-like symptoms. Tell your doctor about your exposure and whether you have a high risk factor.

Michigan Reports Their First H3N2v Case

 

Washtenaw & Ingham County

 

# 6496

 

 

To no great surprise, another state has been added to the list of places where H3N2v flu virus – once again linked to swine exposure at a county fair – has been detected in humans. 

 

This time it is south-central Michigan, and while the child resides in Washtenaw County, the exposure took place at the neighboring Ingham County Fair.

 

Today the Washtenaw County Health Department posted the following notice on their website:

 

Influenza A (H3N2) Variant Virus Identified in Washtenaw County

A human case of an influenza virus that normally infects pigs has been identified in a Washtenaw child. The child was exposed to swine at the Ingham County Fair in early August. This case is the first identified in Michigan. Most cases identified in other parts of the country have also been linked to agricultural events and fairs. The Washtenaw child is recovering.

 

Washtenaw County Public Health reminds all persons to use basic prevention to prevent the spread of illnesses and to use extra caution when in contact with animals. If you or your children have been exposed to pigs recently and are experiencing flu-like symptoms, please contact your health care provider.

 

In recent weeks we’ve seen more than 180 similar cases reported out of Ohio and Indiana (see CDC H3N2v Briefing), and thus far, the CDC has found no evidence of sustained and efficient community transmission.

 

As this virus appears to be fairly well entrenched in pig populations across the Midwest, and would appear fairly easily transmitted from pigs-to-humans, additional cases are likely to crop up as the fall county & state fair season continues.

 

Based on the prior history of this virus, limited human-to-human transmission may also have occurred in some instances. But thus far this virus hasn’t demonstrated the ability to sustain transmission in the community.

 

That could change over time, of course. Which is why emerging viruses like this require special attention. 

 

For now, the public health threat from this virus remains low. The CDC is not advising county fairs to shut down swine exhibitions, but has issued guidance to Fair organizers on how to reduce the risk of infection. 

 

 

Issues for Fair Organizers to Consider When Planning Fairs

Thousands of fairs take place across the United States each year, providing a fun venue for people to interact and show off their livestock, horticulture or agriculture projects. As you organize your local or state fair, you need to be aware of important information to help protect visitors and livestock. This information can help prevent illnesses associated with animals in public settings. This fair season, CDC is monitoring the occurrence of influenza caused by a specific H3N2 influenza virus that has been found in both people and pigs in a number of states. Some simple precautions are effective in reducing the spread of the virus—these include:

1. Visitors to fairs and exhibitions, particularly to the animal barns including pigs, should receive information about disease risks and recommendations to protect visitors and animals from illness.
2. Whenever possible, facilities should minimize human-animal contact. For detailed information refer to the NASPHV Animal Contact Compendium.

   (Continue . . . )

 

 

While these cases are not particularly alarming, there will be a good deal of interest to see whether this virus manages to compete with the seasonal flu strains that we expect to return this winter.

In the short run, I fully expect to see the case counts continue to rise, and it is likely additional states will be added to the list. 

 

As the numbers increase, I’ll endeavor to update the table in my sidebar:

Today’s CDC H3N2v Briefing

 

Credit Wikipedia

 

# 6486

 

The CDC held a press briefing earlier this afternoon to address the recent increase in H3N2v cases detected across Indiana, Ohio, and today . . . Illinois.  Dr. Joseph Bresee, of the CDC’s Influenza Division, gave a short statement and then took reporter’s questions.

 

The transcript will be posted on the CDC’s media site (HERE) later today.  But for now, a few highlights.

 

As has been widely reported, the number of confirmed H3N2v cases over the past week in the Midwest have increased sharply, from 16 reported last Friday to 145 reported today.

 

The lone case in Utah occurred in March, and is not part of this current outbreak.

These numbers are likely to increase over the coming days, as more cases get tested.  Individual states are now doing their own lab confirmation, and releasing results, and so the CDC’s numbers will only be updated once a week (Fridays).

 

While a five-fold increase in cases may look alarming, the CDC believes most of these cases come as the result of direct contact with pigs, not from human-to-human transmission.

While they concede that some `limited’ human-to-human transmission may have occurred in this outbreak, the vast majority of cases so far have had some sort of direct contact with pigs, or their environment.

 

As Dr. Bresee emphasized, “This is not a pandemic situation”.

 

All of the recent cases are genetically similar, meaning they are all swine H3N2 with the M (matrix) gene from the 2009 H1N1 virus.

 

It is thought that this M gene may help increase transmissibility of swine viruses among humans, but that this virus has not adapted sufficiently well to humans to be easily spread.

 

This virus remains sensitive to antivirals (oseltamivir and Zanamivir).

At this time, the CDC does not see the need to ask fairs to cancel or restrict the showing of pigs. Instead they are advising those who are in contact with pigs follow these recommendations:

 

• Wash your hands frequently with soap and running water before and after exposure to animals.
• Never eat, drink or put things in your mouth in animal areas.
• Children younger than 5 years, people 65 years and older, pregnant women, and people with certain chronic medical conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions) are at high risk from serious complications if they get influenza. These people should consider avoiding exposure to pigs and swine barns this summer, especially if sick pigs have been identified.
• If you have animals – including swine – watch them for signs of illness and call a veterinarian if you suspect they might be sick.
• Avoid close contact with animals that look or act ill, when possible, and
• Avoid contact with pigs if you are experiencing flu-like symptoms.

 

 

While there is obviously a lot of concern in the press and among the public, the bottom line is that unless and until this virus adapts sufficiently to spread easily among humans – it doesn’t represent a major public health threat.

 

The hallmark of influenza viruses, of course, is that they are constantly changing.  What we can say was true about a virus yesterday, may not hold true tomorrow.

 

And so public health officials will watch this emerging flu strain carefully for any signs that the situation is changing. 

 

Regardless of how this swine virus plays out, the CDC’s advice to practice good `flu hygiene’ (hand washing, covering coughs & sneezes, staying home if sick) - and to get the flu shot each fall - remain your best strategies against the multiple strains of influenza that circulate each year.

Illinois Confirms One H3N2v Case

Coles County, Illinois

# 6485

 

In what I expect will become an increasingly common occurrence, another state (Illinois) has confirmed an H3N2v infection, this time in a child who attended the Coles County Fair last week.

 

The child has not been hospitalized, and an investigation is underway to try to determine how this child contracted the virus.

 

The CDC will provide an update to the press at 1pm today in anticipation of the release of updated numbers in tomorrow’s FluView Report.

 

Here is the press release from the Illinois Department of Health.

 

 

State Health Department Confirms H3N2v Influenza Case

Common flu precautions recommended

SPRINGFIELD – The Illinois Department of Public Health (IDPH) laboratory has confirmed one case of what is known as the H3N2v influenza virus, which has now been reported in four states this year – Hawaii, Illinois, Indiana and Ohio. IDPH is working with local, state and federal health officials, including the Centers for Disease Control and Prevention (CDC), the U.S. Department of Agriculture, the Illinois Department of Agriculture and the Coles County Health Department, to identify how a child, who attended the Coles County Fair, contracted the virus last week. This child has not been hospitalized. CDC is conducting additional laboratory testing.

 

H3N2v is a variant form of influenza A, which was first detected in 2011. The CDC is currently reporting more than a dozen cases in the U.S. this year, but CDC will update its numbers later today and they are expected rise dramatically. Most infections have occurred following contact with swine, and cases of the virus being transmitted from person to person are rare. So far, the severity of illnesses associated with this virus in people has been similar to the severity of illnesses associated with seasonal flu virus infections.

 

“The H3N2v virus is relatively new, but the Illinois Department of Public Health, the Illinois Department of Agriculture and our federal partners are monitoring this situation closely,” said IDPH Director Dr. LaMar Hasbrouck. “We want you to enjoy your time at the state or county fair, so one key thing to do to stay healthy is to wash your hands frequently, especially if you are around swine.”

 

The state health department and the state agriculture department have increased hand washing stations on the fair grounds and provided guidance and prevention recommendations to fair exhibitors, local health departments and health care providers. The department of agriculture looks at every animal at the state fair grounds and a veterinarian is on site.

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Ohio Updates Their H3N2v Numbers

 

 

# 6482

 

Earlier we learned of a major increase in the number of confirmed H3N2v cases in the state of Indiana, and now we have an update from the Ohio Department of Health indicating a doubling (to 30) of confirmed cases since Monday.

The announcement appears on their Health Tips For Ohio Fairs webpage.

Health Tips for Ohio's Fair Season

The Ohio Department of Health (ODH) along with local health departments have identified several human cases of Influenza A variant H3N2 in Ohio. There are currently 30 cases of H3N2v statewide; all individuals had direct contact with swine at fairs and no human-to-human passage of the virus has been confirmed.

The case breakdown per county is as follows:

• Butler: 16
• Clark: 3
• Gallia: 4
• Greene: 4
• Hamilton: 3

Those with confirmed cases of H3N2v are between the ages of 6 months and 36 years old. To date, one of the confirmed cases was hospitalized as a precaution, but they have since been treated and released.

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As with the earlier announcement out of Indiana, there are more cases being tested, and these numbers are likely to climb.

 

Ohio: CDC Confirms Additional Cases Of H3N2v

 

Cases in Butler County (14) & Clark County (1)

# 6477

 

This afternoon the Ohio Health Department announced that five more people, who were exposed to pigs, have tested positive for the swine H3N2v virus. 

 

Fourteen cases have now been identified in Butler County, and one in Clark County.  Their ages range from 3 to 36. None of these cases have required hospitalization.

 

Of note, the single case from Clark county is associated with the Ohio State Fair – which closed on Sunday - while all of the others are associated with the Butler County Fair.  

 

Last Friday we learned that 2 hogs from the Ohio State fair had tested positive for swine influenza, and had been sent home (see 2 pigs at state fair have swine flu – Columbus Dispatch). So far, the Clark county case is the only infection to be traced to that fair.

 

Here is the press release from the Ohio Department of Health (ODH)

 

ADDITIONAL H3N2v CASES IN OHIO CONFIRMED BY CDC

Ohioans Encouraged to Take Precautions, Prevent Spread of Influenza

COLUMBUS — The Ohio Department of Health (ODH) today announced that additional cases of Influenza A variant H3N2 have been confirmed by the Centers for Disease Control and Prevention (CDC). There are currently 14 humans cases identified in Butler County, linked to swine exposure at the Butler County Fair; and one confirmed human case in Clark County, linked to swine exposure at the Ohio State Fair. Those with confirmed cases of H3N2v are between the ages of 3 and 36 years old, and to date, none of the confirmed cases have resulted in hospitalization. 

On Monday, ODH hosted a statewide conference call with all local health departments to provide an update on the situation.  Local health departments have been urged to work with agriculture and fair officials to post necessary signage and to speak directly with those working in livestock facilities to ensure necessary care is taken to avoid further transmission of the H3N2v strain.

 
ODH continues to partner with local health departments and health care providers across the state on any reports of human influenza-like illness. Individuals who have reported close contact with swine and are exhibiting flu-like systems will undergo testing. Samples will be sent to the ODH laboratory for preliminary testing and then to CDC for confirmation. ODH will provide notice of any additional H3N2v human case confirmations.

 

The Ohio Department of Agriculture (ODA) is actively working with industry partners to assist with public education efforts and to increase the number of hand sanitation stations available at county fairs.  ODA will make contact this week with each upcoming fair veterinarian instructing them to post signage for both the exhibitors and for the visiting public, to closely monitor swine health and to take temperatures of any ill swine and notify ODA immediately of the results.  ODA will continue to swab and test animals as needed throughout the fair season.

 

With county fairs running into the first week of October in Ohio, ODA and ODH remind residents and visitors that fair attendance is safe. Those attending the fair should remember:

• Wash your hands frequently with soap and running water before and after exposure to animals.
• Never eat, drink or put things in your mouth in animal areas, and don’t take food or drink into animal areas.
• Young children, pregnant women, people 65 and older and people with weakened immune systems should be extra careful around animals.
• If you have animals – including swine – watch them for signs of illness and call a veterinarian if you suspect they might be sick.
• Avoid close contact with animals that look or act ill, when possible.
• Avoid contact with swine if you are experiencing flu-like symptoms.

More information is available from ODH at: http://bit.ly/OhioH3N2vUpdates.

 

 

It is likely, as these epidemiological investigations continue, that we will hear of additional infections with this emerging variant virus.

 

So far, the CDC has not found evidence of sustained and efficient human-to-human transmission of this swine variant virus, and all of the recent cases have involved direct contact with pigs.

 

You’ll find additional information on the CDC’s  H3N2v Webpage:

 

Information on Influenza A (H3N2) Variant Viruses (“H3N2v”)

 

 

Ohio’s State Health Department has also put up a webpage on this variant flu, with advice on how to stay healthy while visiting county fairs this fall.

 

Health Tips for Ohio's Fair Season

 

For more background on swine variant viruses, you may be interested in reading these recent blogs:

 

A Variant Flu Review

Novel Viruses & Chekhov’s Gun