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Avian Influenza Detected at Año Nuevo State Park

A small number of young northern elephant seals at Año Nuevo State Park recently tested positive for H5N1, also known as bird flu. This is the first detection of H5N1 in California’s marine mammal population.

The risk of H5N1 to the public remains very low. We’re sharing guidance on how to protect yourself, your pets and marine mammals – and how you can help.

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Elephant seal
northern elephant seal with snotty nose

Human influenza A Virus H1N1 in Marine Mammals in California, 2019

  • Infectious disease

Abstract

From 2011–2018, we conducted surveillance in marine mammals along the California coast for influenza A virus (IAV), frequently detecting anti-influenza antibodies and intermittently detecting IAV. In spring 2019, this pattern changed. Despite no change in surveillance intensity, we detected IAV RNA in 10 samples in March and April, mostly in nasal and rectal swabs from northern elephant seals (Mirounga angustirostris). Although virus isolation was unsuccessful, IAV sequenced from one northern elephant seal nasal swab showed close genetic identity with pandemic H1N1 IAV subclade 6B.1A.1 that was concurrently circulating in humans in the 2018/19 influenza season. This represents the first report of human A(H1N1)pdm09 IAV in northern elephant seals since 2010, suggesting IAV continues to spill over from humans to pinnipeds.


Plancarte, M., Kovalenko, G., Baldassano, J., Ramírez, A.L., Carrillo, S., Duignan, P.J., Goodfellow, I., Bortz, E., Dutta, J., van Bakel, H. and Coffey, L.L., 2023. Human influenza A virus H1N1 in marine mammals in California, 2019. PloS one, 18(3), p.e0283049.

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