FluView & Variant Flu Update: Week 36

 

 

 

# 6555

 

I’m sitting in on the AMA/IDSA Pandemic Preparedness webinar this morning, so this will be a quick update.

The CDC has released their weekly FluView and Variant Flu update, and the number of new H3N2v flu cases shows only a small increase (n=9) over last week.

 

 

 

This week’s FluView has details on these 9 cases, plus one additional H1N1v case identified in  Missouri.

 

2011-2012 Influenza Season Week 36 ending September 8, 2012

Novel Influenza A Virus:

From July 12 through September 13, 2012, a total of 305 infections with influenza A (H3N2) variant (H3N2v) viruses have been reported from ten states. This is an increase of 9 over last week’s report. Cumulative totals by state since July 15 are: Hawaii [1], Illinois [4], Indiana [138], Maryland [12], Michigan [6], Minnesota [4], Ohio [106], Pennsylvania [11], West Virginia [3], and Wisconsin [20]. Sixteen H3N2v-associated hospitalizations and one H3N2v-associated death have been reported. The vast majority of cases have occurred after prolonged swine exposure, though instances of likely human-to-human transmission have been identified. At this time no ongoing human-to-human transmission has been identified.

 

Public health and agriculture officials are investigating the extent of disease among humans and swine, and additional cases are likely to be identified as the investigations continue. Because of reporting schedules, state totals posted by CDC may not always be consistent with those reported by state health departments. If there is a discrepancy between state and CDC case counts, data from the state health department should be used as the most accurate number.

 

As a result of enhanced surveillance activities for H3N2v, one infection with an influenza A (H1N1) variant (H1N1v) virus has been detected in Missouri in a patient who became ill after contact with swine. The patient has recovered from their illness. Confirmatory testing at CDC identified H1N1v with the matrix (M) gene from the 2009 H1N1 influenza virus in specimens collected from this patient. Cases of H1N1v have been detected previously, and the current case marks the second report of H1N1v with the M gene from the 2009 H1N1 virus. This H1N1v case, in addition to the H3N2v cases outlined above and the H1N2v cases reported previously, brings the total number of variant influenza virus infections detected since July 2012 to 309.

CDC & ICAAC Updates On H3N2v

 

 

# 6550

 

 

A bit of a twofer today, as we’ve two videos featuring the CDC’s Dr. Lyn Finelli discussing the recent emergence of the H3N2v swine-origin virus, and how to reduce the risk of it spreading.

 

First stop, a 6-minute  podcast, released earlier this week by the CDC, called:

 

CDC Recommendations to Reduce the Risk of H3N2v Flu Virus Infection for Fairgoers and Swine Exhibitors

You’ll find a video of this podcast, and the transcript, available at the above link.

 

The second video comes from the closing day of 2012’s ICAAC conference in San Francisco, where Dr. Finelli is interviewed by Jeff Fox in a 30 minute presentation.

 

 

Dr. Finelli indicates that, out of the 300 or so new human cases of H3N2v infection this summer, about 10 instances of human-to-human transmission have been detected.  

So far, the vast majority of cases have had direct, and prolonged contact with swine.

 

Complicating matters, we now have four cases of a different swine variant virus – H1N2v – recently detected in Minnesota. 

 

And much like the newly emergent H3N2v virus – this reassortant swine flu has picked up the M gene segment from the 2009 H1N1 virus (see CDC Updates Minnesota H1N2v Cases).

 

 

In another related story, on Monday we learned (see PNAS: Virulence & Transmissibility Of H1N2 Influenza Virus In Ferrets) that Korean researchers had detected a swine flu H1N2 strain that produced serious (even lethal) illness in ferrets, and spread easily among then. 

 

For more on this story, Robert Roos of CIDRAP wrote last night:

 

Ferret study underlines persistent threat of swine flu viruses

Robert Roos News Editor

Sep 11, 2012 (CIDRAP News) – A Korean-US research team has identified an H1N2 strain of swine influenza capable of killing ferrets and spreading among them by respiratory droplets, underlining the continuing threat of swine flu to humans amid a wave of swine-origin flu cases in Americans exposed to pigs at agricultural fairs.

(Continue . . . )

 

 

The concern has long been that swine are highly susceptible to the influenza virus, and are capable of serving as `mixing vessels’, allowing them to reassort into new hybrid strains. 

 

Since end of  the 2009 H1N1 pandemic we’ve begun to see reassortments of other swine flu viruses (H3N2 & H1N2) with genetic elements picked up from the previously `humanized’ H1N1 pandemic strain.

 

 

For now, these reassortant viruses haven’t evolved into efficiently transmitted human flu strains, and so their public health impact is limited. 

 

The caveat being, that as this virus jumps to humans it could begin to `figure us out’, and become more easily transmissible.

 

Which is why the CDC, along with local & state health departments, plan to remain vigilant this fall and winter as they look for any signs of increased human transmission.

CDC Updates Minnesota H1N2v Cases

Credit Wikipedia

 

# 6542

 

A week ago we learned of three human infections with the H1N2v virus in Minnesota, which - while of swine origin – is a different strain than the one behind the cluster of nearly 300 H3N2v infections we’ve been watching over the summer (see Minnesota Reports Swine H1N2v Flu).

 

H1N2 is one of three swine influenza viruses that are commonly found in pigs, the others are H1N1 and H3N2. Until last week, since 2005, only 2 cases of human infection with trH1N2 (now called H1N2v) had been detected in humans.

 

The three cases reported last week are similar to the 2 previous cases, with the exception that the H1N2v virus – like H3N2v – has picked up the M gene segment from the 2009 H1N1 pandemic virus.

The CDC has previously stated that `This M gene may confer increased transmissibility to and among humans, compared to other variant influenza viruses.’

 

All of which serves as prelude to today’s update from the CDC on the H1N2v virus:

 

H1N2 Variant Virus Detected in Minnesota

September 7, 2012 -- The Minnesota Department of Health has reported detection of 3 infections with an influenza A H1N2 variant (“H1N2v”) virus with the pandemic M gene from the 2009 H1N1 virus. These cases were reportedly associated with prolonged contact with pigs at a fair. H1N2 viruses normally circulate in pigs, not people, but rare human infections with this virus have been detected in the past. This virus is different from the H3N2v virus that, as of today, is reported to have caused 296 human infections across 10 U.S. states since July 2012. These additional human infections underscore the fact that swine influenza viruses can spread to people after close contact with infected pigs, and support the importance of ongoing surveillance for both human and swine influenza viruses.

 

According to the state of Minnesota, each of the 3 people infected with the H1N2v virus had exhibited pig(s) or spent prolonged time with pig(s) at the Minnesota State Fair. Two of the three people had underlying health conditions that placed them at high risk of serious flu complications; one of the two people with high risk factors was hospitalized, highlighting again the importance of the CDC recommendation that people with high risk factors avoid close contact with pigs and pig arenas at fairs this season. All 3 people have recovered from their illnesses.

People who are at high risk of serious flu complications include children younger than 5 years, people 65 years and older, pregnant women, and people with certain long-term health conditions (like asthma and other lung disease, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions). A full list of high risk factors is available on the CDC seasonal flu site.

 

In addition to avoiding pigs and pig arenas at fairs this year, as always, people with high risk conditions who develop flu-like symptoms should seek prompt medical attention. The H1N2v virus should be susceptible to both currently recommended influenza antiviral drugs [oseltamivir (Tamiflu®) and zanamivir (Relenza®)].

 

CDC has confirmed the Minnesota samples as H1N2v viruses. Sequencing of the viruses indicates these H1N2 variant viruses are very similar to those found in humans previously; with the exception of the addition of the pandemic M gene. This is the first time this virus has included the M gene from the 2009 H1N1 pandemic virus when isolated from a person. Genetic analysis shows that the hemagglutinin (H) of this virus is similar to human seasonal influenza viruses that circulated in people as recently as 2009, so there would likely be protective immunity against this particular virus in the human population.

 

The University of Minnesota Veterinary Diagnostic Lab also isolated an H1N2 virus from swine sampled at the Minnesota State Fair. Sequencing at National Veterinary Services Laboratories in Ames, Iowa, confirmed that it matches the human isolates from Minnesota. According to the USDA Swine Influenza Surveillance program, very similar H1N2 viruses – also containing the pandemic M gene – have been found in pigs since early 2010 in Minnesota and a number of other U.S. states.

 

 

If you missed it, earlier this week in An Increasingly Complex Flu Field, we looked at some of the new `players’ on the viral field, including the H1N2v virus.

 

And for an excellent overview of the risks of new flu viruses emerging from swine operations, I can heartily recommend Helen Branswell’s  Scientific American article from December of 2010 called:

 

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, 2011 

CDC Variant Flu Update & FluView Week 35

Credit CDC – 9/7/12 Update

 

# 6541

 

 

The CDC has updated their case counts of human infections with the swine H3N2v virus, indicating another 8 cases have been confirmed, along with 1 additional hospitalization. 

 

 

This is the second week in a row with a relatively low increase in the number of new confirmed infections, although it should be mentioned that there remain a number of `suspected or probable cases’ that are not in today’s tally.

 

Pennsylvania, for instance, is reporting 11 confirmed cases, but lists another 30 `probable’ on their website this morning.

 

And it is likely that many mild, or sub-clinical cases simply go untested. 

 

The CDC’s Assessment of the situation reads:

 

CDC Assessment

It's possible that sporadic infections and even localized outbreaks among people with this virus will continue to occur. While there is no evidence at this time that sustained human-to-human transmission is occurring, all influenza viruses have the capacity to change and it's possible that this virus may become widespread. 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. Limited serologic studies indicate that adults may have some pre-existing immunity to this virus while children do not. CDC is closely monitoring human infections with all novel influenza viruses, including H3N2v viruses, and will provide more information as it becomes available.

 

Even if you consider the gaps in surveillance, and likely under-reporting of infections from this virus, H3N2v obviously isn’t spreading anything like the H1N1pdm09 virus did during its debut in the spring of 2009.

 

To put this into perspective, we are roughly 7 weeks since the first clusters began to appear in the Midwest (July 12th, 2012), and we are (just barely) below 300 confirmed cases across 10 states. 

 

The following blast from the past shows the number (and wide geographic spread) of 2009 H1N1 virus detections being reported to the World Health Organization in early June 2009, roughly 7 weeks after it was first detected. 

 

Influenza A(H1N1) - update 45

8 June 2009 -- As of 06:00 GMT, 8 June 2009, 73 countries have officially reported 25,288 cases of influenza A(H1N1) infection, including 139 deaths.

There were, by the way, plenty of gaps in testing and surveillance for the H1N1 virus back in 2009 as well.  The numbers reported above are generally considered to be an undercount.

 

While the H3N2v virus may very well develop `legs’ over time - and eventually pose a larger public health threat - right now it obviously isn’t spreading anything like its H1N1pdm cousin did.

 

Today’s FluView Report has a summary of the novel H3N2v activity and the three H1N2v cases reported last week (see Minnesota Reports Swine H1N2v Flu)

 

 

2011-2012 Influenza Season Week 35 ending September 1, 2012

All data are preliminary and may change as more reports are received.

Novel Influenza A Virus:

From July 12 through September 6, 2012, a total of 296 infections with influenza A (H3N2) variant (H3N2v) viruses have been reported from ten states. This is an increase of 8 over last week’s report. Cumulative totals by state since July 15 are: Hawaii [1], Illinois [4], Indiana [138], Maryland [12], Michigan [5], Minnesota [2], Ohio [102], Pennsylvania [11], West Virginia [3], and Wisconsin [18]. Sixteen H3N2v-associated hospitalizations and one H3N2v-associated death have been reported. The vast majority of cases have occurred after prolonged swine exposure, though instances of likely human-to-human transmission have been identified. At this time no ongoing human-to-human transmission has been identified.

 

<SNIP>

As a result of enhanced surveillance activities for H3N2v, three infections with influenza A (H1N2) variant (H1N2v) virus have been detected in Minnesota in patients who became ill after contact with swine. One patient was hospitalized, but all have recovered from their illness. Confirmatory testing at CDC identified H1N2v with the matrix gene from the 2009 H1N1 influenza virus in specimens collected from all three patients. Although cases of H1N2v have been detected previously, the current cases mark the first reports of H1N2v with the matrix gene from the 2009 H1N1 virus.

 

Otherwise, surveillance of flu activity around the country shows very little activity, despite the scattered reports of H3N2v in the Midwest.

 

 

And the 122 Cities Pneumonia & Influenza mortality surveillance continues to indicate deaths are running well below the seasonally adjusted epidemic level.

 

Pneumonia and Influenza (P&I) Mortality Surveillance:

During week 35, 5.6% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 6.5% for week 35.

 

 

With cooler weather on the way, another 6 to 8 weeks of state and county fairs (mostly in the south), and schools now going back into session, we’ll be watching closely to see if this two-week decline in new cases is a temporary lull, or a sustained trend.

 

Stay tuned.

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 . . .