#17,555
While avian flu viruses (e.g. H5N1, H5N6, H3N8, etc.) are currently viewed as our biggest zoonotic flu threat, not all that far behind are the swine variant viruses (typically H1, H2, H3 viruses), which occasionally spill over from pigs to humans, mostly during the summer and fall `agricultural fair season'.
Swine are viewed as excellent `mixing vessels' for influenza viruses, due to having both mammalian α2,6 receptor cells and avian-like α2,3 receptor cells, and having frequent contact with humans and birds. They are often infected with human seasonal flu, along with their own swine flu viruses.
It is this ability that has recently raised concerns that avian H5N1 might find pigs to be a suitable host (see Netherlands Risk Assessment & Warning of Swine As `Mixing Vessels' For Avian Flu), a concern bolstered last May by the discovery of the (H5N1) Seroconversion of a Swine Herd at a `mixed species' farm (poultry & swine) in Italy.
H1N2 variant [A/California/62/2018] Jul 2019 5.8 5.7 Moderate
H3N2 variant [A/Ohio/13/2017] Jul 2019 6.6 5.8 Moderate
H3N2 variant [A/Indiana/08/2011] Dec 2012 6.0 4.5 Moderate
In 2021 the CDC ranked a Chinese Swine-variant EA H1N1 `G4' as having the highest pandemic potential of any flu virus on their list (see EID Journal: Zoonotic Threat of G4 Genotype Eurasian Avian-Like Swine Influenza A(H1N1) Viruses, China, 2020).
Today's report from Oakland County officials isn't about a human infection, but rather the discovery that pigs displayed at a county fair agricultural exhibit (which ran from July 7-16, 2023) have tested positive for influenza A (subtype not given).
It is a little surprising that 3 days after the discovery the subtype has not been identified, although a full genomic analysis can take much longer. Hopefully those details will be available soon.
Meanwhile county health officials are engaged in contact tracing of exhibitors, and are also warning the public to be aware of potential exposure, and to seek medical advice if they become symptomatic.
The full press release follows:
Influenza Detected in Pigs at Oakland County Fair
Post Date:07/17/2023 4:57 PM
Pontiac, Mich., – The Michigan Department of Agriculture and Rural Development and Department of Health and Human Services have notified Oakland County Health Division that several pigs present at the Oakland County Fair tested positive for influenza A virus, the causative agent of swine influenza.
The pigs began displaying symptoms on July 14 at the fair which took place July 7-16 at Springfield Oaks County Park in Davisburg and is organized and managed by the Oakland County 4-H Fair Association. The swine barn closed to the public that evening. No human cases of swine flu have been reported in Michigan this year. The Health Division is working with state partners and fair management to contact trace and monitor exhibitors and fair staff who were exposed. In the meantime, out of an abundance of caution, the county is notifying the public who may have visited the swine barn.
“Fairgoers who visited the swine barn and develop respiratory symptoms are encouraged to talk to a health care provider and report potential exposure to infected swine,” said Dr. Russell Faust, Oakland County medical director. “Physicians are reminded to consider swine influenza in persons presenting with symptoms, even during the warmer months when seasonal influenza cases are low.”
Swine influenza (flu) is a respiratory disease in pigs caused by type A influenza viruses. Swine flu viruses don't usually infect humans, but human infections have been reported. People cannot get swine influenza from eating properly prepared pork or handling pork products – only from contact with an ill pig.
Symptoms of swine flu in people are like seasonal flu and may include fever, cough, runny nose, and sometimes body aches, nausea, vomiting, or diarrhea. Symptoms usually appear within three days of exposure but can occur for up to 10 days. On rare occasions, swine flu in humans can lead to severe illness such as pneumonia or death.
Those at higher risk of developing complications if they get swine influenza include children younger than 5 years, people 65 years and older, pregnant women, and people with certain chronic health issues, such as asthma, diabetes, heart disease, weakened immune systems and neurological conditions. There is no vaccine for swine flu, and the seasonal flu vaccine will not protect against it. Antiviral drugs such as Tamiflu and Relenza, however, are effective in treating swine flu. Early treatment works best and may be especially important for people with a high-risk condition.
Additional subtyping, including whole genome sequencing, will be performed by the National Veterinary Services Laboratories (NVSL) in Ames, Iowa. The expected turnaround time is approximately three weeks.
For media inquiries only please contact Bill Mullan, Oakland County public information officer, at 248-858-1048.
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 altogether.
Due to growing concerns, last month the CDC held a webinar for clinicians on recognizing, treating, and reporting zoonotic (avian & swine) influenza cases in the community (see COCA Call : What Providers Need to Know about Zoonotic Influenza).
While the public health risk from swine flu viruses is currently thought to be low, these viruses continue to reinvent themselves as they circulate in pigs, which makes them unpredictable and worthy of our attention.
