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#14,018
Mid-June marks the start of our state and county fair season in the U.S., and for nearly a decade, that has meant an uptick in human novel flu infections from exposure to pigs.
Over the past 15 years we've seen more than 460 confirmed human infections with these swine-origin variant viruses, with 2/3rds of those reported in 2012.
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| Swine Variant Human Cases : 2010-2018 - Credit CDC |
Ten day's ago we saw the first reported case of 2019 (see CDC FluView Week 21: 1 Novel (H1N1v) Flu Infection - Michigan)- in an adult > 65 years of age who, a bit unusually, reported no recent contact with live pigs.
The CDC's general risk assessment of these swine variant (H1N1v, H1N2v, H3N2v) viruses reads:
CDC Assessment
Sporadic infections and even localized outbreaks among people with variant influenza viruses may occur. All influenza viruses have the capacity to change and it’s possible that variant viruses may change such that they infect people easily and spread easily from person-to-person. The Centers for Disease Control and Prevention (CDC) continues to monitor closely for variant influenza virus infections and will report cases of H3N2v and other variant influenza viruses weekly in FluView and on the case count tables on this website
While most people who contract swine variant influenza will experience only mild to moderate illness, and these viruses haven't (so far) developed the ability to spread in an efficient and sustained manner in the community, the CDC takes these outbreaks very seriously.
Serious illnesses have occurred, requiring hospitalization, and a couple of deaths have been reported. And of course, there is always the possibility that one of these viruses could evolve into being more easily transmissible in humans.
H3N2 Variant:[A/Indiana/08/11] is among the 16 novel viruses currently being tracked by the CDC's IRAT (Influenza Risk Assessment Tool) Rankings, and while its severity would likely be low-to-moderate, it has the third highest `emergence score' (n=6.0) on their list.Since the influenza subtypes that commonly circulate in swine (H1, H2 & H3) are also the same HA subtypes as have caused all of the human pandemics going back 130 years (see Are Influenza Pandemic Viruses Members Of An Exclusive Club?), when swine variant viruses jump to humans, it tend to get our attention.
While we don't know how prevalent swine-origin flu will be in pigs this summer, the CDC does have some advice for anyone planning on exhibiting pigs, or attending a swine exhibition (below).
Pigs can be infected with 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. The Centers for Disease Control and Prevention (CDC) recommends people take the following actions to help prevent the spread of flu between pigs and people.
CDC Recommendations for People with High Risk Factors:
CDC Recommendations for People Not at High Risk:
- Anyone who is at high risk of serious flu complications planning to attend a setting where pigs will be present should avoid pigs and swine barns.
- 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).
People with high risk factors who develop flu symptoms should call a health care provider. Tell them about your high risk factor and any exposure to pigs or swine barns you’ve had recently. Human seasonal flu vaccine will not protect against commonly circulating swine influenza viruses, but prescription influenza antiviral drugs can treat infections with these viruses in people.
- Don’t take food or drink into pig areas; don’t 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.
- 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 minimizing contact with pigs and wearing personal protective equipment like protective clothing, gloves and masks that cover your mouth and nose when contact is required.
- 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.
- To further reduce the risk of infection, minimize contact with pigs in the pig barn and arenas.
- Watch your pig (if you have one) for illness. Call a veterinarian if you suspect illness.
- Avoid contact with pigs if you have flu symptoms. Wait to have contact with pigs until 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.
For more information, visit Stay Healthy at Animal Exhibits.
In mid-May the CDC released updated Guidance for Human Infections with Swine Flu Viruses so that clinicians would know how to treat, and report, suspected cases. This update also included an Expert Medscape Commentary.
In the fall of 2017, we looked at an EID Journal Dispatch (Transmission Of Swine H3N2 To Humans At Agricultural Exhibits - Michigan & Ohio 2016), that found while widespread illness in pigs was only rarely reported, surveillance revealed an average prevalence of influenza A in fair pigs of 77.5%.
This study cautioned that this suggests `. . . that subclinical influenza A infections in pigs remain a threat to public health (3).'In other words, healthy looking pigs can carry, and transmit swine-variant viruses. We saw similar findings in a 2012 study (see EID Journal: Flu In Healthy-Looking Pigs).
While none of this would dissuade me from visiting a state or county fair this summer (assuming I was so inclined), I would take the CDC's advice seriously, and practice good `fair hygiene' and avoid the pig barn if I fell into any of the high risk categories (which I do).For more on Swine-variant influenza viruses - both in the United States and around the world - you may wish to revisit the past blogs:
Trop. Med & Inf. Dis.: Mammalian Pathogenicity and Transmissibility of H1 Swine Variant Influenza
BMC Vet.: Novel Reassortant H1N2 & H3N2 Swine Influenza A Viruses - Chile
J. Virology: Pathogenesis & Transmission of H3N2v Viruses Isolated in the United States, 2011-2016
JVI: Divergent Human Origin influenza Viruses Detected In Australian Swine Populations
The `Other' Novel Flu Threat We'll Be Watching This Summer
Emerg. Infect. & Microbes: Novel Triple-Reassortant influenza Viruses In Pigs, Guangxi, China
