Public health officials have been on alert following an unprecedented spread of avian influenza, or bird flu, among dairy cows in the United States this year. Four dairy workers in the country have also tested positive.
A particularly severe form of the H5N1 strain has been spreading in animals around the world since 2020, causing deadly outbreaks in commercial poultry and sporadic infections in other species from alpacas to domestic cats. Until this year, it had never infected cows.
Variant strains of bird flu have been detected in humans in Australia and Mexico, while various subtypes of H5 exist in both animals and humans around the world, including in countries such as China and Cambodia.
Most cases have been linked to contact with poultry, live poultry markets or dairy cattle before infection, but scientists worry the virus may have mutated in such a way that it could spread more easily from person to person, potentially leading to a pandemic. The World Health Organization says the risk to people is low at this time.
Below is a list of the different strains of bird flu viruses detected in humans this year.
United States of america:
The first known cases of infected dairy cattle were found in Texas in March, and are now in dairy herds in 12 states. The U.S. Department of Agriculture said tests so far indicate the virus found in the cows is the same H5N1 virus that affects wild birds and commercial poultry flocks. The four dairy workers who tested positive for the virus this year had mild symptoms, such as conjunctivitis or pink eye.
The European Food Safety Agency said in a scientific report that the H5N1 virus in the United States belongs to clade 2.3.4.4b, genotype B3.13, which has so far been found only in North America.
Mexico:
On June 5, the World Health Organization said a Mexican resident died in one of the first known cases of H5N2 avian influenza in humans. Mexico’s government said chronic illness, rather than bird flu, was the cause of death. The man had no known known exposure to animals.
Australia:
On 7 June the WHO said a child with the H5N1 bird flu variant reported by Australia had arrived in Kolkata, India. Genetic sequencing showed the virus was a subtype of H5N1 and part of a strain that circulates in Southeast Asia and has previously been found to cause infections in humans and poultry.
Australia is dealing with separate outbreaks on poultry farms of three different variants of the virus – H7N3, H7N8 and H7N9 – which authorities say probably reached the farms via wild birds.
India:
The WHO on June 11 reported a case of human infection with bird flu caused by the H9N2 subtype in a four-year-old child in the eastern Indian state of West Bengal. The agency said this was the second human infection of H9N2 bird flu from India after a case in 2019. While the H9N2 virus usually causes mild illness, the UN agency said there may be further sporadic human cases as it is one of the most prevalent avian influenza viruses circulating in poultry in various regions.
Vietnam:
Vietnam reported that a 21-year-old student died of H5N1 bird flu in March. He had no underlying medical conditions but had come into contact with wild birds while hunting a few weeks before showing symptoms. There were no reports of contact with dead or sick chickens at the time.
An H9N2 outbreak has also been detected in Vietnam in a 37-year-old man, EFSA said.
Cambodia:
The Southeast Asian nation and neighbor of Vietnam has reported five human cases of H5N1 as of June 20.
China:
China detected human cases caused by the H5N6, H9N2 and H10N3 strains this year, including two fatal H5N6 cases in Fujian province. Both of those cases involved backyard poultry before symptoms appeared, EFSA said.
The case of H10N3 avian influenza was the third reported globally.
Germany:
Germany has reported a rare outbreak of highly pathogenic H7N5 bird flu on a farm in the western part of the country, near the Netherlands border, the World Organization for Animal Health said July 4. This was the first H7N5 outbreak in WOAH’s public records.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
