Saturday, August 06, 2022

CDC: Update On First Human Infection with Flu Virus from Pigs During 2022



Two days ago we saw a report from the West Virginia Department of Health on their investigation into a Presumptive Swine Variant (H3N2v) Illness connected to a swine exhibit at a county fair, which was followed by a brief statement in yesterday's CDC FluView. 

Practically every summer since 2010 we've seen small (and sometimes, not-so-small) outbreaks of swine-variant influenza, usually connected to county and state fairs. 

It is common enough, that in anticipation of this year's agricultural fair season, 2 weeks ago I wrote a blog called Swine Variant Flu Seasonwhich reviewed some of the history of these outbreaks. Some years we see only a handful of cases, while others (like 2012) can produce hundreds. 

The pandemic risk from these viruses is consider low, but not zero.  

The 2009 H1N1 pandemic arose when a swine flu virus jumped to humans, and so it could happen again. The CDC currently lists 3 North American swine variant viruses as having at least some pandemic potential. 

After two years of the COVID pandemic restrictions, our community immunity to influenza viruses is believed low - and there are reports of moderately increased swine influenza activity this summer -  which may put us at a higher than normal risk for outbreaks this fall. 

Late yesterday the CDC published a much longer report on the Swine-variant case in West Virginia, and on swine variant viruses in general.  You'll find excerpts below, but you'll want to follow the link to read it in its entirety.

CDC Confirms First Human Infection with Flu Virus from Pigs During 2022

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August 5, 2022—CDC has reported the first human infection with an influenza (flu) virus that usually spreads in pigs occurring during 2022. The person had direct contact with pigs at an agricultural fair, where pigs tested positive for flu A. Recent reports of an increase in swine flu outbreaks in pigs in the U.S. suggest the risk of exposure and infection with these viruses may be higher than usual this fair season, which can last into the fall. CDC recommends people take precautions around swine, including in the fair setting.

Every year, there are rare sporadic human infections with flu viruses that usually spread in pigs. When found in people, these are called “variant flu virus” infections and designated with the letter “v” after the subtype. Variant flu virus infections are usually associated with contact with pigs, often at agricultural fairs. While these types of infections usually cause mild illness, they are concerning because they can cause severe illness, especially in people at higher risk of serious flu complications, and because of their potential to cause a flu pandemic.

The first variant flu virus infection of 2022 was reported by West Virginia and occurred in a person younger than 18 years who participated in an agricultural fair and had contact with pigs. An investigation is still ongoing but findings to date include:
  • The infected person was not hospitalized and is recovering from their illness.
  • The variant virus is a flu A H3N2v virus, based on RT-PCR testing done at CDC.
  • Pigs at this fair tested positive for flu A.
  • There have been reports of respiratory illness among other people who attended the same agricultural event. Specimens from other patients are being forwarded to CDC for additional testing.
  • To date, no person-to-person spread of this virus has been confirmed.
Agricultural fairs take place across the United States every year, primarily during the summer months and into early fall. Many fairs have swine exhibitions, where pigs from different places come into close contact with each other and with people. These venues may increase the risk of spread of flu viruses among pigs and between pigs and people due to these interactions.

CDC Recommends Precautions while Attending Agricultural Fairs

People who are at higher risk for developing serious flu complications  should avoid pigs and swine barns at fairs. If they cannot avoid exposure to pigs, they should wear a well-fitting mask that covers the nose and mouth to reduce their risk of exposure to flu viruses. They should also wash their hands with soap and running water before and after exposure to pigs or a swine barn. If soap and water are not available, they should use an alcohol-based hand rub.

For people who are not at higher risk of serious flu complications, prevention measures to limit the spread of flu viruses include:
  • Not eating or drinking while in pig areas,
  • Avoiding contact with pigs that appear to be sick, and
  • Washing hands often with soap and running water before and after contact with pigs.
People should take additional protective measures if they must come in contact with pigs that are known or suspected to be sick. This includes minimizing contact time with pigs and wearing personal protective equipment like protective clothing, gloves, and well-fitted masks that cover the mouth and nose when contact is required.

Note that seasonal flu vaccines are not formulated to protect against variant flu viruses, but the same flu antiviral drugs used to treat seasonal flu can be used to treat variant flu virus infection in children and 

While county and state fair agricultural exhibits are very popular, the CDC advises those who are at higher risk of serious flu complications (including children under 5, adults over 65, pregnant women, and those with certain chronic medical conditions), to avoid pigs and the swine barn.