Saturday, August 10, 2019

4th Michigan Fair Reports Swine Influenza in Pigs


Mid-summer and early fall is county and state fair season for much of the country, and over the past 10 years that has been associated with a spate of human infection with swine variant influenza viruses (H1N1v, H1N2v, H3N2v).

While it is almost certainly a significant under-count, over the past 15 years we've seen more than 460 confirmed human infections with these swine-origin flu viruses, with 2/3rds of those reported in 2012.

Swine Variant Human Cases : 2010-2018  - Credit CDC
The CDC's general risk assessment of these swine variant 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
The last human case was reported in May (see CDC FluView Week 21: 1 Novel (H1N1v) Flu Infection - Michigan), but two weeks ago we saw reports of Swine Influenza At Fowlerville Family Fair (Michigan), followed last weekend with Michigan: Two More Fairs Report Swine Influenza In Pigs.

Overnight there have been multiple media reports of Swine flu confirmed in pigs at Jackson County Fair (Michigan), following the release (on Facebook) of the following statement from the Jackson County Health Department.

There are hundreds of fairs every summer and fall across the country, and we generally only hear about a handful reporting influenza in pigs, and fewer still resulting in confirmed human infections.

However, 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).
The good news is, despite ample opportunities to jump species, human infection appears relatively rare.
Two months ago we looked at Biosafety At The Fair This Summer, and the CDC's 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:
  • 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).
CDC Recommendations for People Not at High Risk:
  • 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.
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.

For more information, visit Stay Healthy at Animal Exhibits.

While I wouldn't let any of this dissuade me from visiting a state or county fair this summer (assuming I was so inclined), I would certainly 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).