Bird Flu and its impact on humans
What is bird flu, and how it infects humans?

What is bird flu, and how it infects humans?
Avian influenza Type A, or bird flu, is a virus that primarily affects birds. While it’s rare, human infections have occurred with some bird flu viruses. These infections can lead to a range of illnesses, from mild symptoms to severe diseases such as pneumonia, which can be life-threatening. This underscores the importance of understanding and preventing bird flu.
Human infections with bird flu viruses have most often happened after close or lengthy unprotected contact with infected birds (i.e., not wearing gloves, respiratory protection, or eye protection). Human infections with bird flu viruses only happen through an intermediary animal, including cats and cows.
Human infections with bird flu viruses can occur when the virus enters a person’s eyes, nose, or mouth, or is inhaled. This can happen when the virus is airborne in droplets or dust, and a person breathes it in. However, it’s important to note that the spread of bird flu viruses from one infected person to a close contact is very rare and almost never happens. This should provide some reassurance about the limited risk of human-to-human transmission.
The history of bird flu (H5N1 virus)
The CDC summarizes the history of the bird flu as follows. The first description of avian influenza (bird flu) dates to 1878 in northern Italy, when it was described as a contagious disease of poultry associated with high mortality, referred to as “fowl plague.” At the beginning of the century, it was discovered that a virus caused it.
1996 was the year that the highly pathogenic avian influenza (HPAI) H5N1 virus was first identified in waterfowl in Southern China. The virus was named A/goose/Guangdong/1/1996. A new strain of HPAI subtype H5N1 was introduced to poultry via migratory waterfowl in the Guangdong province of China. The new bird flu strain results in a high mortality rate of 40%+ in aquatic fowl.
The year 1997 saw the first human case related to the H5N1 virus during an outbreak in Hong Kong, and it caused severe illness in 18 people, with one-third dying. The outbreak caused more than 860 human infections with a greater than 50% death rate.
After the virus’s outbreak in Hong Kong in 1997, things remained quiet until 2003. The virus faded into the background until 2003/2004 when a large outbreak of H5N1 infections spread through poultry flocks in several Asian countries.
In 2003, H5N1 re-emerged in China and several other countries, causing widespread poultry outbreaks across Asia. In 2005, wild birds spread H5N1 to poultry in Africa, the Middle East, and Europe. The virus’s hemagglutinin (HA) gene diversifies into many genetic groups (clades). Multiple genotypes were detected. During this period, 528 human cases of H5N1 were detected.
The H5N1 virus was detected in Canada and the US in late 2021. A new H5N1 virus belonging to clade 2.3.4.4b with a wild bird-adapted N1 NA gene emerged. By the end of 2021, the Clade 2.3.4.4b H5N1 viruses had become predominant in Asia, Africa, Europe, and the Middle East. In February 2022, the virus caused an outbreak in US commercial and backyard poultry. Rare sporadic human infections with this H5N1 virus are detected, as well as sporadic infections in mammals.
In 2024 the current outbreak was discovered in the US in March. The virus was first detected in dairy cows in Kansas and Texas. Later, it had spread to 16 states. The virus was eventually detected in alpacas and commercial and backyard flocks. In addition to birds, the illness affecting dairy cattle in Texas add was detected as influenza A (H5N1). This was the first time an influenza virus was known to spill over into cows. Human cases discovered among dairy workers.
The first death in Louisiana due to bird flu in the current outbreak
The CDC has reported a rare and concerning incident-one person previously hospitalized with severe avian influenza (H5N1) illness has tragically caused the individual to passed away. This is a stark reminder of the known potential for these viruses to cause severe illness and death. As of January 6, 2025, there have been 66 confirmed human cases of H5N1 flu in the US since 2024 and 67 since 2022. This marks the first H5N1-related death in the US. Outside the US, more than 950 cases of H5N1 bird flu have been reported to the World Health Organization. (World Health Organization) about half of those have resulted in death.
Recently, the CDC data showed mutations in samples of bird flu collected from the Louisiana patient. These mutations, not found in poultry samples collected on the patient’s property, suggest the changes appeared after the patient became infected.
Bird flu in humans
The experts say there is no evidence the virus is currently heading towards an epidemic or pandemic, but there has already been one case of severe disease.
Different genotypes or genetic makeup of the virus could result in more severe cases.
The case in Louisiana was caused by a different genotype, one that has been circulating in the wild birds, and these are much more severe cases.
CNN reported that a child in San Francisco had a probable case of H5N1 bird flu. The case was caught by routine surveillance, and tested positive for influenza A. Sequencing of the child’s sample determined that it was H5N1. The child did not need to be hospitalized, and they have recovered from their illness.
In early July, the US government awarded Modena $176 million to develop and test a bird flu vaccine using mRNA technology. In October, federal health officials announced that they are providing $72 million to vaccine manufacturers to help ensure currently available bird flu vaccines are ready to use if needed. This proactive approach, coupled with the absence of current vaccination recommendations, signifies the potential for change if the virus becomes more transmissible. The US is now better equipped to handle a potential bird flu epidemic or pandemic than it was with COVID-19 in 2020.
Infections in the US and Canada
Since February 2022, the USDA reported the presence of H5N1-infected birds in 1376 poultry flocks, including 623 commercial flocks and 753 backyard flocks. More than 130 million birds from all 50 states have been affected. The virus also is widely distributed across the wild bird population.
Since 2022, the USDA has reported H5N1 in 418 mammals across the country, including deer mice, house mice, domestic cats, mountain lions, coyotes, bottlenose dolphins, foxes, skunks, raccoons, black bears, and others.
As of December 31, 2024, there were 916 confirmed cases in cattle in 16 states: California, Colorado, Idaho, Iowa, Kansas, Michigan, Minnesota, Nevada, New Mexico, North Carolina, Ohio, Oklahoma, South Dakota, Texas, Utah, and Wyoming.
From March 2024 to December 31, 2024, the CDC reported 66 cases of human infections in 10 states: California (37), Colorado (10), Iowa (1), Louisiana (1), Michigan (2), Missouri (1), Oregon (1), Texas (1), Washington (11), and Wisconsin (1). These cases were primarily from dairy and poultry farms. However, it’s important to note that no person-to-person infection was seen.
The CFIA in Canada reported that since December 2021, it has detected 517 infected poultry facilities in nine provinces: Alberta (86), British Columbia (235), Manitoba (24), New Brunswick (2), Newfoundland and Labrador (2), Nova Scotia (8), Ontario (56), Québec (58), and Saskatchewan (46). The Canadian government reported that after implementing stringent measures to prevent the spread of H5N1 that currently (January 04, 2025) there are no cases of H5N1 infections in either humans or cattle have been reported in Canada.
Milk and meat safety in the bird flu time
Pasteurization kills bacteria and viruses, including the H5N1 bird flu virus, in milk. The FDA and USDA are confident that pasteurization is effective in inactivating H5N1 in raw milk. Cooking poultry, eggs, and beef to the appropriate internal temperature kills bacteria and viruses, including H5N1 viruses. Currently, the only known way to get sick with the bird flu is by drinking raw milk or eating undercooked poultry or beef products. In1996 the highly pathogenic avian influenza (HPAI) H5N1 virus was first identified in waterfowl in Southern China.