Friday, August 12, 2022

CDC FluView Week 31: 2 More Novel H3N2v Cases Reported Out of West Virginia




Last week the West Virginia Department of Health reported one presumptive novel H3N2v infection in an individual younger than 18 years who participated who participated in an agricultural exhibit at the Jackson County fair and who had close contact with pigs.

Several other attendees were also reported to have had `influenza-like' symptoms, and an investigation was underway. 

Today the CDC's FluView reports that two more individuals have tested positive for the swine H3N2v virus.

Novel Influenza A Virus

Two human infections with a novel influenza A virus were reported by West Virginia. The patients were infected with an influenza A(H3N2) variant (A(H3N2)v) virus. Both patients are <18 years of age, were not hospitalized, and have recovered from their illness. An investigation by health officials showed that both patients attended an agricultural fair and that swine at this fair tested positive for swine influenza A(H3N2).
No person-to-person spread of this virus has been confirmed to date. This is the third patient infected with an H3N2v virus reported from West Virginia in the past 2 weeks; all three attended the same agricultural fair prior to illness onset.

When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant influenza virus.” Most human infections with variant influenza viruses occur following close proximity to swine, but human-to-human transmission has occurred previously. It is important to note that in most cases, variant influenza viruses have not shown the ability to spread easily and sustainably from person to person.

Early identification and investigation of human infections with novel influenza A viruses are critical so that the risk of infection can be understood and appropriate public health measures can be taken. Additional information on influenza in swine, variant influenza virus infection in humans, and guidance to interact safely with swine can be found at Additional information regarding human infections with novel influenza A viruses can be found at

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 gets our attention.

Most (but not all) swine variant infections are mild or moderate, and are clinically indistinguishable from regular seasonal influenza. Which is why it is believed many swine variant infections go undetected (see CID Journal: Estimates Of Human Infection From H3N2v (Jul 2011-Apr 2012).

In 2012 more than 320 human infections were reported around the nation, while 5 years ago (2016/17) 66 cases were recorded.

 The CDC's Assessment of the Risk from these 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 the pandemic risk from swine variant viruses is currently considered low, the H1N1 pandemic 2009 demonstrated just how quickly the status quo can change. 

Some information for exhibitors at county and state fairs include: