Journal AEM : US Feral Swine Were Exposed To Both Avian & Swine Influenza A Viruses

Feral Swine - Credit USDA

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While scientists monitor commercial swine herds for signs of influenza evolution, relatively little is known about the carriage of influenza A viruses by feral swine in the United States, and around the globe.   

With U.S. feral hog populations tripling over the past 25 years (now est. at 6 million ) scattered across 38 states, these invasive and incredibly destructive creatures are expected to expand to all 50 states in the next few decades  (see 2017 study  Interpreting and predicting the spread of invasive wild pigs).

Swine, as we've discussed often, can be infected by many types of influenza (including swine, human and avian strains), and may be co-infected by two or more viruses at the same time.  This  susceptibility - along with influenza's ability to reassort into new subtypes - makes pigs excellent `mixing vessels' for influenza.

Despite less-than-robust surveillance of commercial swine around the globe, over the past couple of years we've seen a number of new `reassortant' viruses detected in pigs. A few recent blogs include:

I&ORV: Triple-Reassortant Novel H3 Virus of Human/Swine Origin Established In Danish Pigs

Emerg. Microbes & Inf.: Pathogenicity & Transmission Of A Swine Influenza A(H6N6) Virus - China

Front. Microbiol.: A Novel H1N2 Reassorted Influenza Virus In Chinese Pigs

PNAS: The Pandemic Potential Of Eurasian Avian-like H1N1 (EAH1N1) Swine Influenza  

Compared to commercial swine, our understanding of what is going on with influenza in feral pigs is almost non-existent.  We have seen a handful of studies over the years, including a 2008 survey in the Journal of Wildlife Diseases (see Influenza exposure in United States feral swine populations.) which found:

Of the 271 IAV-positive samples, 236 cross-reacted with swine IAVs, 1 with avian IAVs, and 16 with avian and swine IAVs, indicating that feral swine were exposed to both swine and avian IAVs but predominantly to swine IAVs. Our findings suggest that feral swine could potentially be infected with both avian and swine IAVs, generating novel IAVs by hosting and reassorting IAVs from wild birds and domestic swine and facilitating adaptation of avian IAVs to other hosts, including humans, before their spillover. 

 A 2013 EID Journal Dispatch (see Influenza A Subtype H3 Viruses in Feral Swine, United States, 2011–2012), which from 1,989 serum samples collected from 31 states, found that 182 samples were IAV (Influenza A Virus) positive.  They concluded: 

Our study demonstrated that subtype H3N2 IAVs are periodically infecting feral swine in the United States. Feral swine are a potential source of IAVs with bidirectional transmission to domestic swine or humans. Detection of an H3N2v-like IAV in the feral swine population demonstrates a potential threat to human health. Continued surveillance is recommended to monitor the distribution and the genomic and antigenic diversities of IAVs in feral swine to better assess the risk.

All of which serves as prelude to a new study, published last week in the Journal of Applied Environmental Microbiology, that finds U.S. feral hogs have been exposed to a variety of influenza A viruses, including avian subtypes.

US feral swine were exposed to both avian and swine influenza A viruses
Brigitte E. Martina, Hailiang Suna, Margaret Carrelb, Fred L. Cunninghamc, John A. Barochd, Katie C. Hanson-Dorrc, Sean G. Younge, Brandon Schmitd, Jacqueline M. Noltingf, Kyoung-Jin Yoong, Mark W Lutmanh, Kerri Pedersenh, Kelly Lageri, Andrew S. Bowmanf, Richard D. Slemonsf, David R. Smithj, Thomas DeLibertod* and Xiu-Feng Wana*  

ABSTRACT

Influenza A viruses (IAVs) in swine can cause sporadic infections and pandemic outbreaks among humans, but how avian IAV emerges in swine is still unclear. Unlike domestic swine, feral swine are free ranging and have many opportunities for IAV exposure through contacts with various habitats and animals, including migratory waterfowl, a natural reservoir for IAVs.

During 2010--2013, 8,239 serum samples were collected from feral swine across 35 US states and tested against 45 contemporary antigenic variants of avian, swine, and human IAVs; of these, 406 (4.9%) samples were IAV-antibody positive. Among 294 serum samples selected for antigenic characterization, 271 cross-reacted with ≥1 testing virus whereas the other 23 did not cross-react with any testing virus. Of the 271 IAV-positive samples, 236 cross-reacted with swine IAVs, 1 with avian IAVs, and 16 with avian and swine IAVs, indicating that feral swine were exposed to both swine and avian IAVs but predominantly to swine IAVs. 

Our findings suggest that feral swine could potentially be infected with both avian and swine IAVs, generating novel IAVs by hosting and reassorting IAVs from wild birds and domestic swine and facilitating adaptation of avian IAVs to other hosts, including humans, before their spillover. Continued surveillance to monitor the distribution and antigenic diversities of IAVs in feral swine is necessary to increase our understanding of the natural history of IAVs.

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While agricultural exhibitions at state and county fairs make up the vast majority of the swine-human contact in the United States (followed by commercial farms and abattoirs), feral pigs - which are hunted for meat, sport, and animal control - are increasingly in contact with humans. 

Being omnivorous, and free ranging, they also have significant opportunities for contact with IAV infected birds. 

While the odds of that happening may seem long here in the United States, it was only 7 months ago we were following an outbreak of a rarely reported avian H7N2 virus among hundreds of cats (and 1 veterinarian) across several New York City animal shelters (see J. Virology: Virulence Of A Novel H7N2 Virus Isolated From Cats In NYC - Dec 2016).

The H7N2 virus was likely acquired when an unlucky feline dined on the wrong bird in what is arguably the most urban area of the United States.

It that can happen in mid-winter in Manhattan, then it isn't that much of a stretch to imagine it happening among feral hogs in Texas, Florida, or Tennessee.

Just one of the many reasons why I never bet against flu.

The Enigmatic, Problematic H3N2 Influenza Virus

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For the past 10 weeks we've been watching a growing, often severe, out-of-season H3N2 flu epidemic in Southeast China (see Macao, Hong Kong & Guangdong Province All Reporting Heavy Flu Activity) which appears to be hitting Hong Kong the hardest. 

Yesterday, two Hong Kong University infectious disease experts suggested a recent mutation in the H3N2 virus may be one of the contributing factors to this summer flu epidemic (see Hong Kong: HKU Experts Call For Deploying Prophylactic Tamiflu To Avert Crisis).

With much of the reportage in Chinese, we've had to deal with syntax challenged machine translations, but overnight the South China Morning Post reported:

Mutation may be behind surge in flu cases this summer, Hong Kong experts say

Surge in number of cases could be due to variation in dominant strain, which may have rendered vaccines used in past two years ineffective

The operative words in this headline being `may' and `could'.

While several recent amino acid substitutions (including N121K) have turned up recently in H3N2 viruses in Hong Kong (and around the globe), it isn't at all clear how much of a factor they are in Hong Kong's current flu epidemic.

The H3N2 virus, which came to prominence as a pandemic strain in 1968 (supplanting 1957's pandemic H2N2), settled in the following year as a seasonal flu strain and remained the sole human influenza A strain until 1977, when H1N1 mysteriously reappeared after a 20 year absence.

Since then, H3N2 has co-circulated with (first) the old H1N1 strain (until 2009) and then the new H1N1pdm09 strain. Unlike in previous pandemics, the 2009 H1N1 virus did not supplant the existing (in this case, H3N2) influenza A virus. 

All of which makes H3N2 a bit long in the tooth, having been circulating in humans now for nearly 50 years. Over the past five decades it has had to reinvent itself innumerable times (via antigenic drift) to evade acquired immunity, resulting in an increasing number of subclades of the virus co-circulating around the globe.

Since 2009 seven distinct genetic groups have been defined for H3N2.  While all belong to clade 3C, they are divided into three subdivisions; 3C.1 , 3C.2, and 3C.3, with last November's ECDC Influenza Virus Characterization Report stating:

In 2014 three new subclades emerged, one in subdivision 3C.2, 3C.2a, and two in 3C.3, 3C.3a and 3C.3b , with subclade 3C.2a viruses dominating in recent months.

Since then we've seen this newly dominant  3C.2a subclade further split into 3C.2a1 and 3C.2a2 (see Eurosurveillance: Emergence Of A Novel Subclade Of Seasonal A/H3N2 - London). The following Eurosurveillance chart shows the recent evolution of H3N2 clade 3C.

As you can see, both 3C.2a1 and 3C.2a2 share the N121K substitution, which is the `mutation'  referenced in the SCMP article above. This amino acid substitution has increasingly been turning up in the literature over the past 6 months.

Last February, in a Eurosurveillance Rapid communication Interim estimates of 2016/17 vaccine effectiveness against influenza A(H3N2), Canada, January 2017 DM Skowronski  et al. found:

Sequence analysis revealed substantial heterogeneity in emerging 3C.2a1 variants by province and over time. Adjusted VE was 42% (95% confidence interval: 18–59%) overall, with variation by province. Interim virological and VE findings reported here warrant further investigation to inform potential vaccine reformulation. 

In other words, they found the H3N2 vaccine effectiveness was a lackluster 42%, and that the H3N2 virus was evolving at a substantial rate. They write:

In sequencing analysis, we identified considerable diversity among circulating influenza A(H3N2) strains, including a mix of genetic variants that differed geographically and with time.

The majority (80%) of A(H3N2) viruses included in our VE analysis belonged to the newly emerging clade 3C.2a1, but with continuing genetic evolution compared with the vaccine strain. Almost all (95%) 3C.2a1 viruses had both the N171K and N121K mutations in site D that distinguish this clade.

They end by saying:

Conclusion

Continued evolution in circulating 3C.2a variants and their derivatives, and the impact on vaccine protection, warrants ongoing monitoring to inform potential vaccine reformulation.

While a 40% VE is less than we'd like to see, it is far better than what we saw during the 2014-15 flu season when a late arriving `drifted' H3N2 virus practically negated that year's flu vaccine's effectiveness (see CDC HAN Advisory On `Drifted’ H3N2 Seasonal Flu Virus).

We've another study - referenced yesterday by the HKU experts - that found a far lower VE in Denmark for their H3N2 vaccine last winter, along with a very complex mixture of co-circulating H3N2 subclades.

J Clin Virol. 2017 Jun 29;94:1-7. doi: 10.1016/j.jcv.2017.06.007. [Epub ahead of print]

Changes in genetically drifted H3N2 influenza A viruses and vaccine effectiveness in adults 65 years and older during the 2016/17 season in Denmark.

Trebbien R1, Fischer TK2, Krause TG3, Nielsen L4, Nielsen XC5, Weinreich LS6, Lis-Tønder J7, Skov MN8, Christiansen CB9, Emborg HD3.

Abstract

RESULTS:
 
The genetic characterization revealed several genetically drifted viruses, which could be divided into four main clusters by the defining amino acid substitutions: 3C.2a/N121K/S144K, 3C.2a/T131K/R142K, 3C.2a1, and 3C.2a1/N121K.
Some of the drifted viruses appeared to be more prominent in vaccinated or non-vaccinated individuals, respectively. Overall the adjusted VE was 7.4% (95% confidence interval (CI): -6.0-19.2) among inpatients and 19.3% (95% CI: -5.7-38.4) among outpatients, respectively.

VE for the four main virus clusters was; cluster 3C.2a1: 38.8% (95% CI: -29.8-71.1), cluster 3C.2a/N121K/S144K: 9.2% (95% CI: -63.0-49.4), cluster 3C.2a/T131K/R142K: 19.0% (95% CI: -85.3-64.6), and cluster 3C.2a1/N121K: -12.2% (95%CI: -129.7-45.2).

CONCLUSIONS:

Several genetically drifted H3N2 viruses have been circulating in Denmark in the 2016-17 influenza season. An overall low VE was estimated and VE for the four main virus cluster indicate different VEs between the circulating drifted H3N2 viruses.

Copyright © 2017 Elsevier B.V. All rights reserved.

The VE against 3C.2a1 was nearly 40%, but for the remaining three drifted viruses was far lower, with the VE against the 3C.2a1/N121K virus almost nonexistent. These results all come from a cohort of over-65 aged patients, which tend to be the least protected by flu vaccines.

An equally dismal H3N2 VE was reported out of South Korea last winter (see PLoS One Interim estimates of the effectiveness of the influenza vaccine against A(H3N2) influenza in adults in South Korea, 2016–2017 season) although they did not provide any genetic breakdown of H3N2 subclades. 

Here in the United States, we saw a modest level of protection (34%) against H3N2, according to the CDC's MMWR report of June 30th.

2016–17 Influenza Vaccine Effectiveness

Data collected through the U.S. Influenza Vaccine Effectiveness Network during November 28, 2016–April 14, 2017, indicate that influenza vaccination this season reduced the overall risk for influenza-associated medical visits by 42% (95% CI = 35%–48%). Vaccine effectiveness against the predominant influenza A(H3N2) viruses was 34% (95% CI = 24%–42%) and vaccine effectiveness against influenza B viruses was 56% (95% CI = 47%–64%).

This fall's northern hemisphere flu vaccine will use the same (A/Hong Kong/4801/2014-like) H3N2 virus as last year's formulation, but will add a new H1N1 strain. Its effectiveness in preventing H3N2 infection this year may well depend upon which `flavor' of the H3N2 virus visits your region this winter.

The evolution of flu viruses - particularly H3N2 - is so rapid that it is impossible to know with any certainty what subtype - much less what subclade - will be dominant six months from now. 

And the strain that is king of the viral mountain in North America in January may not be on top in Europe, or Asia. Which means, by the time flu arrives in your area, this fall's H3N2 vaccine component could do better, worse, or about the same as last year. Guaranteed.

I'll certainly get the flu vaccine this year (as I do every year), but given the increasing genetic diversity of the H3N2 virus and the severity of Hong Kong's outbreak, the advice offered by DM Skowronski et al. in the conclusion of their Eurosurveillance report above is something we probably all ought to take to heart this fall.

Given that a substantial proportion of vaccinated people may remain unprotected against influenza A(H3N2) illness, other adjunct measures should be considered to minimise associated morbidity and mortality, particularly among high-risk individuals.

While it may not be as effective as we'd like, the flu vaccine – along with practicing good flu hygiene (washing hands, covering coughs, & staying home if sick) – remains your best strategy for avoiding the flu and staying healthy this winter.

And if you do get sick, early administration of antivirals - particularly for high-risk individuals - can make a real difference in severity, duration, and outcomes.

Italy Reports Two New Outbreaks Of H5N8

Credit Wikipedia

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While greatly reduced over the past 3 months, we continue to see scattered outbreaks of HPAI H5N8 in Europe. In June we saw outbreaks reported in Belgium, Luxembourg, France, and the UK (see ESA Epidemiological Update: HPAI H5 Clade 2.3.4.4 Viruses In Europe).

Today Italy's Istituto Zooprofilattico Sperimentale delle Venezie has confirmed a pair of outbreaks in Mantua Province, in northern Italy.

Highly pathogenic avian influenza (HPAI) in Italy

2016/2017 - H5N5, H5N82016 - H7N72014/2015 - H5N8, H5N12013 - H7N7

2016/2017 – H5N5, H5N8

• Outbreaks | PDF (last update: 21/07/2017)
• Map | PDF (last update: 21/07/2017)

July 2017

21/07/2017  – On 20 July, the National Reference Laboratory (NRL) for Avian Influenza and Newcastle Disease confirmed as positive for Avian Influenza virus subtype H5N8 two farms located in Lombardy region: a rural holding and a fattening turkey industrial farm in Mantua province. Epidemiological investigations are ongoing in both outbreaks. An increase in mortality was reported in the previous days in one of the sheds of the industrial farm where about 18.900 fattening female turkeys (106 day-old) were present. Further information on virus characterization and on the cases will be provided as soon as available.

In the same date, Regional Authority of Lombardy notified a suspect of avian influenza in a laying hens farm (500.000 heads) in Mantua province.

Today, the NRL characterised both the viruses as Highly Pathogenic Avian Influenza.

The persistence of HPAI H5N8 in wild birds well into the summer - even at relatively low levels - is a decided change over what we've seen in previous years with this particular avian virus.

In 2015, after North America's biggest avian epizootic on record, the virus all but disappeared in the wild, and hasn't been reported in North American flocks in over two years (see PNAS: The Enigma Of Disappearing HPAI H5 In North American Migratory Waterfowl).

But the virus that returned to Europe last fall had acquired significant changes (via reassortment) during the summer of 2016. In addition to being far more virulent in wild and migratory birds (see Europe: Unusual Mortality Among WIld Birds From H5N8), it also displayed the ability to infect a much wider range of birds (see ESA list of 78 species).

All of which means that we can't rely on the old `rules' necessarily applying going forward.       

HK CHP Notified Of A Single H7N9 Case In Jiangsu Province

Jiangsu Province - Credit Wikipedia

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For the third week in a row China's NHFPC reports a single new H7N9 case over the past 7 days, this time in Jiangsu province.

CHP notified of human case of avian influenza A(H7N9) in Jiangsu

 

     The Centre for Health Protection (CHP) of the Department of Health is today (July 21) monitoring a notification from the National Health and Family Planning Commission that one additional human case of avian influenza A(H7N9) was recorded from July 14 to 20 in Jiangsu, and strongly urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.

     The 62-year-old female patient in Nanjing was known to have exposure to live poultry market and had onset on July 12.

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Hong Kong: HKU Experts Call For Deploying Prophylactic Tamiflu To Avert Crisis

Flu Express - Severe Flu Week 28

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Hong Kong's out-of-season flu epidemic continues to worsen (see yesterday's Week 28: Hong Kong's Flu Activity Increases To `A Very High Level') with their Centre for Health Protection (CHP) announcing no fewer than 3 new institutional outbreaks, and another severe pediatric case, over night.

• CHP investigates case of severe paediatric influenza A infection
• Cluster of Influenza A cases in Queen Elizabeth Hospital
• Cluster of Influenza A cases in Caritas Medical Centre
• CHP investigates influenza A outbreak in elderly home in To Kwa Wan

Also overnight, and causing quite a stir in the local media, two Hong Kong University infectious disease experts - Yuen Kwok-yung and David Christopher Lung - called upon the government to release 14-day prophylactic courses of  the antiviral drug Tamiflu (tm) - aka oseltamivir - to vulnerable elderly people to avert a crisis.

This from RTHK News:

Use Tamiflu urgently to control flu cases: experts

2017-07-21 HKT 12:00

Two infectious disease experts have called on the government to immediately administer the antiviral drug Tamiflu to vulnerable elderly people to control the current flu outbreak.

The microbiologists from the University of Hong Kong, Yuen Kwok-yung and David Christopher Lung, jointly issued a warning on Friday, saying that the public healthcare system is "on the verge of collapse" due to the summer flu cases.

In a jointly authored article, published in local newspaper Ming Pao, they said the season's peak will probably last at least two more weeks, and the government must act more aggressively to rein in the disease.

         (Continue . . . )

Similar reports appear in the Hong Kong Standard and other English language media outlets. Both of these experts are heavyweights in the world of influenza.

Professor Yuen, Kwok Yung 袁國勇

Title:

Chair of Infectious Diseases

Professor (Clinical)

Henry Fok Professor in Infectious Diseases

Dr LAM Chi Leung David

Clinical Assistant Professor

BSc (BioMedSc) (HK), MBBS (HK), MRCP (UK), FHKCP, FHKAM (Medicine), PhD (HK), FRCP(Edin & Glasgow), FCCP, FACP.

Oseltamivir can be used both for treatment and for prophylaxis, either post or pre-exposure. It is rare, however, to see such a `blanket' recommendation for prophylaxis for at risk individuals across an entire city.

The original article (in Chinese) is available at this link.  In it, these scientists discuss a mutation in the H3N2 virus that may be responsible for this summer's unusual epidemic (translation follows):

(1) viral factors: 2014/15-year-H3N2 influenza A winter peak was due to the emergence of antigenic drift (antigenic drift), but the epidemic of H3N2 influenza is not to drift. According to the recent Danish study showed that 2016/17 H3N2 influenza in a small antigenic variation (N121K), this variation has the potential to influenza vaccine used in the past two years failed.

Hong Kong H3N2 influenza A strains also appeared N121K variation, from July 2016 to March 2017, about 20% of the H3N2 strain appears N121K variation, while in May 2017, more than 35 percent of H3N2 strains N121K variation occurs. This variation may be the peak of the flu this summer one of the reasons.

This N121K variation has previously been linked to diminished vaccine effectiveness with the 3C.2a1 clade of the H3N2 virus, which we looked at in Eurosurveillance: Interim Estimates Of Flu Vaccine Effectiveness Against A(H3N2) - Canada, January 2017 and  Eurosurveillance: Emergence Of A Novel Subclade Of Seasonal A/H3N2 - London.



So far I've not seen any official response by the CHP or Hong Kong authorities.

Second Ohio County Fair Closes Hog Barn Over Swine Flu

Franklin County - Credit Wikipedia

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Last Friday we saw Clinton Co. Ohio Fair Close Hog Barn Over Swine H3N2, sending 200 market hogs to slaughter early.  Yesterday it was announced (h/t Shiloh on FluTrackers) that two hogs at the Franklin County Fair (Columbus, Ohio) had tested positive for swine H1N1, and that their exhibit had been closed as well. 

While swine influenza can sometimes jump to humans (where it is then dubbed a `swine variant' virus), so far, we've no reports of human infections from either of these two outbreaks.  

Two reports, then I'll return with a bit more on why we monitor outbreaks like these so closely.  First, from the Columbus Dispatch:

Influenza outbreak leads to slaughter of pigs at Franklin County Fair

By Marion Renault

After at least two hogs tested positive for swine influenza, almost 50 pigs on exhibit at the Franklin County Fair were removed Wednesday evening for slaughter.

Livestock areas have been disinfected and no swine flu is present on the fairgrounds, the Franklin County Agricultural Society said in a Facebook post Thursday afternoon. The fair will continue as planned through Saturday. 

“The Ohio Department of Agriculture was contacted immediately and every protocol was followed,” the post said. “Anyone coming to the fairgrounds can feel comfortable that the grounds are safe.”

(Continue . . . )

 And this statement from the Franklin County Agricultural Society:
 

STATEMENT FROM THE FRANKLIN COUNTY AGRICULTURAL SOCIETY:

The Ohio Department of Agriculture has confirmed two hogs tested positive for influenza at the Franklin County Fair.

Thanks to the proactive communication from of our Fair leadership and 4H advisors, our exhibitor was able to quickly identify an issue with his hogs and report it to the attending veterinarian. The Ohio Department of Agriculture was contacted immediately and every protocol was followed.

On Wednesday evening, out of an abundance of caution, all hogs were removed from the fairgrounds for harvest. All 48 were what we call market pigs, meaning they were already slated for market – to be processed.

The livestock areas were again disinfected, and the Fair will continue through Saturday, July 22. We do not presently have swine flu on the fairgrounds. Anyone coming to the fairgrounds can feel comfortable that the grounds are safe.

The 4H exhibitors showing the hogs will still participate in the livestock auction on Saturday, July 22, rewarding months of hard work and dedication.

“We followed, and continue to follow, every protocol per the Ohio Department of Agriculture to ensure the health of our animals, and most importantly, our exhibitors and fairgoers” says David Fleshman, president, Franklin County Agriculture Society. “We are grateful to everyone for exercising caution and acting in the best interest of our Fair and our community.”

Anyone who visited the Franklin County Fair and experiences flu-like symptoms, should contact a medical professional.

As a reminder to those visiting our livestock areas for the remainder of the Fair, we ask the following:

– Wash and/or sanitize hands thoroughly and often, particularly after handling animals and always before eating meals or touching your mouth (Hand washing/sanitizing stations can be found throughout the livestock barn, for convenience)
– No food or drink is allowed in the livestock barns
– No strollers, sippy cups or pacifiers are allowed in the livestock barns

Influenza viruses (primarily swine H1N1, H3N2, and H1N2) circulate commonly in swine herds, and while there is always a concern that one of these viruses could someday evolve  into a more `humanized' strain (as happened with H1N1 in 2009) - most of the time these infections are mild, and don't pose much of a threat to the pigs or the public.

But when infected pigs are brought into agricultural exhibits at county fairs, they can share flu viruses with other pigs (with a risk of reassortment) and are placed into a public venue where hundreds, even thousands, of visitors could be potentially exposed. 

Hence the closure, out of an abundance of caution, of these two exhibits.

Most years fewer than a dozen `swine variant' infections are reported  in the United States, mostly involving farm or livestock workers. Most are mild, but many others probably go undiagnosed.

During the summer of 2012 we saw our largest outbreak to date, with 10 states reporting more than 300 confirmed cases, nearly all linked to county or state fair attendance (see H3N2v Update: CDC Reports 52 New Cases, Limited H2H Transmission).

Indiana reported the most cases (n=138), followed by Ohio (n=106).  While the H3N2v virus was the most commonly reported strain, H1N1v and H1N2v were also detected.

While most of these infections were mild, 16 people were hospitalized and 1 died (see MMWR: H3N2v Related Hospitalizations In Ohio – Summer 2012). Two years later, during a far less active swine flu year, FluView Week 17 reported A Fatal Swine Variant (H1N1v) Case In Ohio. 

And over this past winter, we looked at two severe swine variant flu infections in Europe (see here and here).  While rare, serious, even fatal infections can occur. 

Last August, over a period of several weeks, we followed reports of 18 people - all fair attendees - who were diagnosed with a swine variant (H3N2v) influenza virus in two states; Michigan and Ohio.  Among those blogs:

CDC FluView: 7 More H3N2v Cases (4 Michigan, 3 Ohio) In Week 33

Ohio: More Reports Of H3N2 In Exhibition Swine

CDC: Interim Guidance for Clinicians on Human Infections with Variant Influenza Viruses

Last October, from the MMWR: Investigation Into H3N2v Outbreak In Ohio & Michigan - Summer 2016, we learned that that 16 of the 18 cases analyzed belonged to a new genotype not previously detected in humans. From the report's summary:

What is already known about this topic?

Sporadic human infections and outbreaks with influenza viruses that normally circulate in swine have occurred in the past. The largest known outbreak of H3N2v virus infections occurred in 2012.

What is added by this report?

In August 2016, 18 laboratory-confirmed infections with H3N2v virus were reported among persons who had attended agricultural fairs in Michigan and Ohio. Sixteen of the 18 cases occurred in persons who were infected with a reassortant H3N2v virus that contained a hemagglutinin (HA) gene previously not detected in variant viruses.

The HA gene was likely introduced from humans into swine in 2010 or 2011, and viruses with this gene have circulated and evolved in swine to be genetically and antigenically different from both previous and currently circulating human seasonal influenza A(H3N2) viruses.

What are the implications for public health practice?

To minimize transmission of influenza viruses from swine to humans and from humans to swine, agricultural fair organizers should consider measures such as shortening the time swine are on the fairgrounds to ≤72 hours, immediately isolating ill swine, maintaining a veterinarian on call for the duration of the swine exhibition, providing prominent handwashing stations, and prohibiting food and beverages in animal barns. Persons at high risk for influenza-associated complications should be discouraged from entering swine barns.

The CDC maintains a comprehensive Swine/Variant Influenza page where you'll find the latest case counts, safety and prevention information, and guidance for health care providers.

Some information for exhibitors at county and state fairs include:

• Key Facts for People Exhibiting Pigs at Fairs[545 KB, 2 pages]
• Take Action to Prevent the Spread of Flu Between People and Pigs[1.3 MB, 2 pages]
• Educational Posters[389 KB, 1 page]
• Compendium of Measures to Prevent Disease Associated with Animals in Public Settings, 2013.
• Reduce Your Risk (English)[22 KB, 1 page] | (Spanish)[22 KB, 1 page]
• Measures to Minimize Influenza Transmission at Swine Exhibitions, 2016 – NASAHO and NASPHV[97 KB, 8 pages]

And for some earlier blogs on the evolution of swine viruses, you may wish to revisit:

PNAS: The Pandemic Potential Of Eurasian Avian-like H1N1 (EAH1N1) Swine Influenza

Eurosurveillance: Seroprevalence Of Cross-Reactive Antibodies To Swine H3N2v – Germany
JID: Evolutionary Dynamics Of Influenza A Viruses In US Exhibition Swine

Live Markets & Novel Flu Risks In The United States