#16,952
For the 3rd week in a row the CDC's FluView is reporting on a novel swine flu infection, but unlike the 3 previous cases this month, this patient did not report having contact with swine or attending an agricultural exhibit at a fair.
While most swine variant viruses have a limited ability to spread from person-to-person, we occasionally see cases where no direct epidemiological links to swine can be established, raising the possibility of limited H-2-H transmission.
This case is also the first H1N2v infection reported in 2022, as the previous cases have all been H3N2v. Since 2010, only about 6% of swine variant viruses detected in the United States have been H1N2v, while nearly 90% have been H3N2v.
Most cases have been reported in the Midwest, with Indiana and Ohio accounting for roughly 60% of all cases.
This appears to be Oregon's first case.
Novel Influenza A Virus
A human infection with a novel influenza A virus was reported by the Oregon Health Authority. The patient was infected with an influenza A(H1N2) variant (A(H1N2)v) virus. The patients is <18 years of age, was not hospitalized, and has recovered from their illness. An investigation by local public health officials did not identify contact with swine or agricultural fair attendance by the patient prior to illness onset. Additional investigation did not identify respiratory illness in any of the patient’s household contacts. No person-to-person spread of this virus has been confirmed to date associated with this case. This is the first patient infected with an H1N2v virus reported in the United States in 2022.
A total of four human infections with a variant influenza A virus have been reported in the United States in 2022, including three H3N2v (West Virginia) and one H1N2v (Oregon).
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 can occur. 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 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 Assessment of the Risk from these viruses reads:
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 threat from swine variant viruses is currently believed low, 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 Moderate
H3N2 variant [A/Indiana/08/2011] Dec 2012 6.0 4.5 Moderate
The CDC maintains a comprehensive Swine/Variant Influenza page where you'll find the latest case counts, safety and prevention information, and guidance for health care providers, including:
- Key Facts for People Exhibiting Pigs at Fairs[545 KB, 2 pages]
- Take Action to Prevent the Spread of Flu Between People and Pigs[1.3 MB, 2 pages]
- Educational Posters[389 KB, 1 page]
- Compendium of Measures to Prevent Disease Associated with Animals in Public Settings, 2013.
- Reduce Your Risk (English)[22 KB, 1 page] | (Spanish)[22 KB, 1 page]
