HPAI H5N1 (Avian Influenza)

According to the Centers for Disease Control and Prevention (CDC), "Avian influenza or bird flu refers to the disease caused by infection with avian (bird) influenza (flu) Type A viruses. These viruses naturally spread among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Bird flu viruses do not normally infect humans. However, sporadic human infections with bird flu viruses have occurred."

The Highly Pathogenic Avian Influenza (HPAI) strain of the H5N1 avian flu is currently spreading in the U.S. and is the same as the one spreading in Europe and Asia. Both wild birds and domestic poultry have been affected, along with cases of the virus being found in wild mammals, such as foxes, mink, skunks, bears, sea lions, and otters. Few cases of H5N1 in cats have also been reported. Most recently in the spring of 2024, multiple US states reported infection of H5N1 in herds of dairy cows. Three cases have been reported in humans in the U.S. (1 in Colorado in 2022, 1 in Texas and 1 in Michigan in 2024). 

The CDC further explains "the wide geographic spread of A(H5N1) bird flu viruses in wild birds, poultry, and some other mammals, including in cows, is creating additional opportunities for people to be exposed to these viruses. Therefore, there could be an increase in sporadic human infections resulting from bird, cattle, and other animal exposures, even if the risk of these viruses spreading to people has not increased. Sporadic human infections in the current context would not significantly change CDC’s risk assessment." 

As of April 19, 2024, the CDC "is collaborating with partners including the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), and state public health and animal health officials to address this emerging infectious disease."

According to the World Health Organization,  on "May 23, 2024, the Mexico International Health Regulations (IHR) National Focal Point (NFP) reported to PAHO/WHO a confirmed fatal case of human infection with avian influenza A(H5N2) virus detected in a resident of the State of Mexico who was hospitalized in Mexico City. This is the first laboratory-confirmed human case of infection with an influenza A(H5N2) virus reported globally and the first avian H5 virus infection in a person reported in Mexico. Although the source of exposure to the virus in this case is currently unknown, A(H5N2) viruses have been reported in poultry in Mexico." 

• Centers for Disease Control & Prevention
• World Organisation for Animal Health
• National Emergening Special Pathogens Training & Education Center
• World Animal Health Information System 
• FAQs: USDA APHIS

• Fatal human case of H5N2 in Mexico 
• Current Bird Flu Situation in Wild Birds (CDC)
• Current Bird Flu Situation in Poultry 
• Current H5N1 Bird Flu Situation in Dairy Cows (CDC)
• Current U.S. Bird Flu Situation in Humans (CDC)

• 4/2/2024 Statewide Briefing: H5N1 in Dairy Cows 
• 4/16/2024 Statewide Briefing: Influenza Virus A 101 | H5N1 
• 4/26/2024  H5N1: Gauging the Current Threat  (Brown University: School of Public Health) 
• 4/29/2024  Region 7 Special Pathogen Outbreak Report: Highly Pathogenic Avian Influenza (RESPTC & R7DHRE)
• 4/30/2024 Statewide Briefing: H5N1- FDA Testing, Dairy Cows, & Prevalence in Milk 

Data was sourced and imported from FAO EMPRES, USDA APHIS, WAHIS, and open source news reports beginning in late 2022 to current.

• Climate change impacts on bird migration and highly pathogenic avian influenza

Prosser, D.J., Teitelbaum, C.S., Yin, S. et al. Climate change impacts on bird migration and highly pathogenic avian influenza. Nat Microbiol 8, 2223–2225 (2023). https://doi.org/10.1038/s41564-023-01538-0

• Zoonotic Mutation of Highly Pathogenic Avian Influenza H5N1 Virus Identified in the Brain of Multiple Wild Carnivore Species

Vreman, S.; Kik, M.; Germeraad, E.; Heutink, R.; Harders, F.; Spierenburg, M.; Engelsma, M.; Rijks, J.; van den Brand, J.; Beerens, N. Zoonotic Mutation of Highly Pathogenic Avian Influenza H5N1 Virus Identified in the Brain of Multiple Wild Carnivore Species. Pathogens 2023, 12, 168. https://doi.org/10.3390/pathogens12020168

• Highly pathogenic avian influenza A(H5N1) virus infection in farmed minks, Spain, October 2022

Agüero Montserrat, Monne Isabella, Sánchez Azucena, Zecchin Bianca, Fusaro Alice, Ruano María José, del Valle Arrojo Manuel, Fernández-Antonio Ricardo, Souto Antonio Manuel, Tordable Pedro, Cañás Julio, Bonfante Francesco, Giussani Edoardo, Terregino Calogero, Orejas Jesús Javier. Highly pathogenic avian influenza A(H5N1) virus infection in farmed minks, Spain, October 2022. Euro Surveill. 2023;28(3):pii=2300001. https://doi.org/10.2807/1560-7917.ES.2023.28.3.2300001

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