Michigan: MDHHS Reports Presumptive-Positive Swine Variant Infection From Oakland County Fair

#17,578

Nine days ago (see Michigan: Oakland County Fair Reports Influenza A Infection In Pigs) we looked at a report on the detection of Influenza A in pigs at a country fair which ran from July 7-16. The subtype was not provided, and samples had been sent on to the National Veterinary Services Laboratories (NVSL) in Ames, Iowa.

While Swine-variant (typically H1N1v, H1N2v, H3N2v) infections are generally mild, and don't transmit very well between people, they are assumed to have at least some pandemic potential, and so local officials urged:

“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.”

Today we are learning from the MDHHS that at least one person - a swine exhibitor at the fair from neighboring Lapeer County, Mi. - has been identified as a probable swine-variant infection.  We also learn that the virus has been partially identified as `H3'. 

First the statement from the MDHHS, then I'll return with a bit more.

MDHHS reports presumptive positive case of influenza A H3 (swine flu) variant detected in Lapeer County resident

July 26, 2023

The Michigan Department of Health and Human Services and Lapeer and Oakland County health departments have identified a presumptive positive human case of influenza A H3 variant (swine flu) in a Lapeer County resident who was an exhibitor at the Oakland County Fair. The fair took place July 7-16 at the Springfield Oaks County Park in Davisburg. A respiratory specimen that tested presumptive positive for swine flu will be sent to the Centers for Disease Control and Prevention (CDC) for confirmatory testing.

Oakland County Health Division has been reaching out to swine exhibitors and their families who visited the swine barns at the Oakland County Fair to identify any additional illnesses in those who may have been exposed to influenza from infected pigs. Oakland County Health Division has already alerted providers in their jurisdiction to watch for patients presenting with respiratory symptoms who report exposure to swine or who visited the fair.

“Visitors of the Oakland County Fair should monitor for flu-like symptoms: fever, respiratory symptoms like cough and runny nose, and body aches, nausea, vomiting or diarrhea,” said Dr. Natasha Bagdasarian, MDHHS chief medical executive. “If you believe you may have the flu, contact your health care provider and stay home until you have recovered.”

Below are some steps you can take to protect yourself and prevent the spread of any illness:Avoid close contact with sick people.

• Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
• Wash hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
• Refrain from eating or drinking in livestock barns or show rings.
• Do not take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.
• Anyone who is at high risk of serious flu complications and planning to attend a fair should avoid pigs and swine barns.
• Avoid touching your eyes, nose, and mouth. Germs spread this way.
• If you are sick, stay home from work or school until your illness is over.
• Avoid contact with pigs if you have flu-like symptoms. Wait seven 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.
• Get an annual influenza vaccination.

Pigs may be infected with swine influenza viruses that are different from human flu viruses. Swine flu viruses spread among pigs and – while rare – they can spread from pigs to people too. Spread of swine flu viruses from a pig to a person is thought to happen in the same way that human flu viruses spread; mainly through droplets when infected pigs cough and sneeze.

Symptoms of variant influenza infection in people are similar to those of seasonal flu viruses and can include fever and respiratory symptoms, such as cough and runny nose, and possibly other symptoms, such as body aches, nausea, vomiting or diarrhea. Infections with influenza viruses (including variant viruses like influenza A H3) can sometimes cause severe disease, even in healthy people.

Severe illness can include complications, such as pneumonia, which may require hospitalization, and sometimes causes death. People who are at high risk of developing complications if they get variant influenza infection include children younger than 5 years of age, people 65 years of age and older, pregnant women and people with certain long-term health conditions, such as asthma, diabetes, heart disease, weakened immune systems and neurological or neurodevelopmental conditions.

The time period it takes from exposure to illness for variant influenza is similar to that of seasonal influenza, which can be up to 10 days, but is most commonly three days. Currently, there is no human vaccine for influenza A H3 and the seasonal flu vaccine will not protect against Influenza A H3; however, prescription antiviral drugs, such as oseltamivir and zanamivir, are effective in treating influenza A H3 virus infections. Early treatment works best and may be especially important for people with a high-risk condition.

For more information, visit CDC.gov/SwineFlu

While lengthy, surprisingly few details on this case provided by this press release.  

• The age, gender, presentation (mild or severe), and current condition of the infected individual are not addressed.  
• Nothing is said about the patients close contacts, or why it has taken > 10 days for the first case to be identified
• It is also a bit unusual that nearly 2 weeks after the discovery of the sick pigs, the full subtype remains unidentified; as it is still being reported only as `H3'. 

While most `H3' swine viruses are `H3N2', new genotypes occasionally emerge (see MMWR: Investigation Into H3N2v Outbreak In Ohio & Michigan - Summer 2016), and sometimes, we even see novel subtypes.

In 2014 we saw `H3N1' identified in at least two states (see USDA IAV-S Surveillance Program Detects Novel H3N1 In US Swine). H3N1 had been known to circulate in pigs for at least a decade (see EID Journal 2006 article Novel Swine Influenza Virus Subtype H3N1, United States), but that new variant was a combination of both human and swine influenza viruses.

So we'll be particularly interested in the results of genomic analysis of this sample from Ames, Iowa. 

Due to growing concerns over swine and avian flu, last month the CDC held a webinar for clinicians on recognizing, treating, and reporting zoonotic 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 thought to be low, these viruses continue to reinvent themselves as they circulate in pigs, which makes them unpredictable and worthy of our attention.