2020–2025 H5N1 outbreak

[5] In late 2023, H5N1 was discovered in the Antarctic for the first time, raising fears of imminent spread throughout the region, potentially leading to a "catastrophic breeding failure" among animals that had not previously been exposed to avian influenza viruses.

[11]: (fig.1) Genetic reassortment of several influenza A strains culminates in the emergence of a highly pathogenic H5N1 subtype bearing the clade 2.3.4.4b hemagglutinin (HA) gene.

[17] A human case of H5N1 was reported in the U.S. in April, "though this detection may have been the result of contamination of the nasal passages with the virus rather than actual infection.

[29] On March 1, 2023, as Taiwan raised its travel alert for Cambodia, the WHO and the U.S. Center for Disease and Control and Prevention (CDC), in concert with Cambodian authorities, determined that both of the individuals had been infected through direct contact with poultry.

[38] In September 2023, Uruguay reported upwards of 400 seals and sea lions found dead of H5N1 on the nation's Atlantic coastline and along the River Plate.

The District Collector decided to initiate the process of culling domestic birds within a 1 kilometre (0.62 mi) radius from the epicentre of the outbreak.

Earlier in the year, the Philippines Department of Agriculture temporarily banned poultry exports from several countries including Japan, Belgium, and France.

[55] As of March 8, 2024, the United States Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) had recorded around 20 mammal species confirmed as being able to be infected by H5N1.

[57][58] On April 2, a dairy worker in Texas became infected, and strong indications of cow-to-cow spread were evident as cow herds in five different states became ill.[59] A few days later, on April 4, H5N1 was confirmed to have spread to several additional dairy herds in six US states, including Texas, along with Idaho, Kansas, New Mexico, Ohio and Michigan.

[63][64] On April 10, researchers found several cases of HPAI H5N1 in animals in New York City, including three Canada geese, a red-tailed hawk, a peregrine falcon, and a chicken.

[67] On April 26, the FDA reported the virus had spread to cow herds in nine states, including Colorado, with one in five U.S. commercial milk samples testing positive for traces of bird flu.

[72] On May 16, the US Department of Agriculture's National Veterinary Services Laboratories confirmed positive tests for the virus in alpacas on a farm in Idaho, who had to be culled.

[81][82][83] As of June 6, infected dairy cows in five states, South Dakota, Michigan, Texas, Ohio, and Colorado, had died from the H5N1 avian flu, with an estimated mortality rate of up to 10%.

[84] Beginning in late June, the USDA launched voluntary pilot programs to test bulk milk tanks on dairy farms in four states: Kansas, Nebraska, New Mexico, and Texas.

Farmers who volunteer for the program were allowed to move their herds across state lines without additional testing if their bulk milk tanks were found negative for H5N1 for three consecutive weeks.

Outbreaks in multiple large poultry facilities and intensive dairy farms led to ten human farm-worker cases being reported in and around the county.

[86] Research conducted in this region showed H5N1 as having the ability to replicate copiously in bovine mammary glands leading to multi-directional intra- and inter-species transmission between cows, humans, cats, birds and a raccoon.

In October 2024, a third farmworker in California has tested positive for bird flu, according to the state's health department, marking the 17th potential human case of H5N1 in the U.S. since March.

The business interests of the heavily corporatised dairy and livestock industries being prioritised over public health and animal welfare was stipulated as the main cause of the failure to control the novel outbreak.

[100] On December 6, the USDA announced a new mandate to test the national milk supply for bird flu as part of efforts to combat the virus's spread among dairy herds.

Beginning December 16, entities handling raw milk, such as dairy processors, would collect and share samples with agricultural officials.

Since March, over 700 dairy herds, predominantly in California, had already been affected, alongside 57 human cases of mild symptoms reported across the country.

The USDA emphasized the program's role in swiftly identifying and controlling outbreaks, ensuring the safety of livestock and public health.

[102][103] On the same day, California governor Gavin Newsom announced a state of emergency due to the rising cases of the bird flu.

[105] In January, a 28 year old man from Kampong Cham province died from H5N1 avian flu infection after possibly consuming symptomatic chickens.

[106] The UK reported a human case of H5N1 avian influenza in late January which was detected in a poultry farm worker.

The victim, an unidentified Louisiana man, had previously been reported sick with the virus in December after being exposed to a combination of infected backyard chickens and wild birds.

As of May, the experimental mRNA vaccine utilizing lipid nanoparticles (LNPs) has worked to protect lab animals from severe illness and death for at least one year prior to the announcement.