#16,176
For the 8th & 9th time in the 2020-21 flu season the CDC is reporting on novel flu infections, this time involving two swine variant viruses (A(H3N2)v and A(H2N1)v) contracted by two unrelated patients younger than 18 years old in Iowa.
Today's report comes just 3 weeks after CDC FluView Week 32 : 2 Novel H1N2v Infections Reported In Wisconsin Fair Goers. In past years, attendance at state and local fairs with agricultural exhibits has often been a risk for infection.
While most swine variant infections don't appear to transmit well in humans, more than 475 cases have been reported in the United States since 2005, including clusters of limited H-2-H transmission.
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
Novel Influenza A Virus
Two human infections with novel influenza A viruses were reported by Iowa: one influenza A(H3N2) variant (A(H3N2)v) and one influenza A(H1N2) variant (A(H1N2v)). Both infections were in individuals who were <18 years of age. Neither of the individuals were hospitalized and both have fully recovered from illness. Investigation into the sources of infections showed that household members of one individual kept or cared for swine and the other individual had direct contact with swine. No human-to-human transmission has been identified associated with either case.
When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant influenza virus”. Nine human infections with a novel influenza A virus have been reported in the United States this influenza season, including two H3N2v (IA, WI), two H1N2v (IA, OH), and five H1N1v (IA, NC, WI (3)) virus infections. Five infections have occurred in children <18 years of age and four have occurred in adults ≥ 18 years of age. All individuals had direct contact with swine, were on a property with swine present, or had a household member who had direct contact with swine prior to illness onset. No human-to-human transmission of variant influenza virus associated with any of the nine cases has been identified.
Early identification and investigation of human infections with novel influenza A viruses are critical so that the risk of infection can be more fully understood and appropriate public health measures can be taken. Additional information on influenza in swine, variant influenza virus infection in humans, and strategies to interact safely with swine can be found at www.cdc.gov/flu/swineflu/index.htm. Additional information regarding human infections with novel influenza A viruses can be found at http://gis.cdc.gov/grasp/fluview/Novel_Influenza.html.
The CDC's IRAT (Influenza Risk Assessment Tool) lists 3 North American swine viruses as having at least some pandemic potential (2 added in 2019).
H1N2 variant [A/California/62/2018] Jul 2019 5.8 5.7 ModerateH3N2 variant [A/Ohio/13/2017] Jul 2019 6.6 5.8 ModerateH3N2 variant [A/Indiana/08/2011] Dec 2012 6.0 4.5 Moderate
The risk of one of these swine variant viruses sparking a pandemic is relatively low, but it isn't zero. After all, a swine-origin H1N1v virus jumped to humans and sparked a mild-to-moderate flu pandemic in 2009.
The CDC currently ranks a Chinese Swine-variant EA H1N1 `G4' as having the highest pandemic potential of any flu virus on their list.
Whether it comes from pigs, poultry (avian flu), bats (coronaviruses, henipaviruses, etc.), or some other animal reservoir, the next pandemic will likely emerge - as did SARS and SARS-CoV-2 - with little or no warning.
Which is why, even as we continue to battle COVID, we need to be preparing for the next pandemic.
