Highly Pathogenic Avian Influenza (HPAI) H5N1

The highly pathogenic avian influenza H5N1 (HPAI H5N1) also known as the Bird Flu, is a zoonotic influenza that infects wild birds. It was first identified in China in 1996. It is spread by bird migration and since then, it has become the dominant strain in bird populations worldwide. 

In the last year it has become transmissible to mammals and has caused a multistate outbreak in dairy cows and other animals in the United States There have been 66 confirmed human cases in the United States in 2024, and on January 6, 2025, the first person in the United States has died from an H5 infection[i]. 

The CDC says the risk to the general public is low because there is no evidence of human-to-human transmission. However, people who work with birds, poultry, or cows, or have recreational exposure to them are at higher risk.

[i]“First H5 Bird Flu Death Reported in United States” Centers for Diseases Control and Prevention, Media Relations, January 6, 2025, https://www.cdc.gov/media/releases/2025/m0106-h5-birdflu-death.html, accessed January 8, 2025

The first human cases of A(H5N1) were in Hong Kong in 1997. As of November 1, 2024, there have been over 900 reported cases of H5N1 in humans in 24 countries since 2003, with a fatality rate of about 52%. It has been confirmed in dairy herds and poultry farms.

- The HPAI is widespread in wild birds worldwide and has also been detected in many backyard poultry flocks.

-  It has been an ongoing multi-state outbreak in dairy cattle. As of January 6, 2025, HPAI has been confirmed in in a total of 16 states with 300 confirmed cases. (California, Colorado, Idaho, Iowa, Kansas, Michigan, Minnesota, North Carolina, Nevada, New Mexico, Ohio, Oklahoma, South Dakota, Texas, Utah, and Wyoming.)

- The HPAI H5N1 has also infected some mammals believed to have eaten infected birds. These include seals, bears, foxes, skunks; farmed mink; stray or domestic animals, such as cats and dogs; and zoo animals, such as tigers and leopards. On October 30, it has been reported to be in a pig in Oregon.

With the re-emergence of the highly pathogenic avian influenza (HPAI H5N1), also known as the bird flu, scientists once again are watching for mutations that can cause another pandemic. 

This is a novel virus to which the world population has no immunity. The death rate of Covid-19 at its height was .0012[i](1.2%) The death rate of HPAI H5N1 globally from January 1, 2003, to November 2024, is 52%.[ii] [iii]

Recent genetic changes show it is close to human-to-human transmission causing great concern. It’s been said that a pandemic caused by this virus would be like a global tsunami, similar to the 1918 Influenza.

[i] “Assessing the Impact of the Covid-19 Pandemic on US Mortality”, Andrew C Stokes, PhD, et al, National Institutes of Health (NIH) (gov). Revised March 22, 2022, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7480051/Accessed October 11, 2024

[ii]“Avian Influenza (Bird Flu)”, Medscape, Nicholas John Bennett, et al., https://emedicine.medscape.com/article/2500029-overview#a2, updated November 26, 2024, accessed January 8, 2025.

[iii]“Human Infection with Avian Influenza A(H5) Viruses,” World Health Organization, https://cdn.who.int/media/docs/default-source/wpro---documents/emergency/surveillance/avian-influenza/ai_20241004.pdf?sfvrsn=5f006f99_142, October 4, 2024, Accessed October 11, 2024.