Countries Where Bird Flu Has Infected Humans as Virus Spreads Globally

The spread of avian influenza, or bird flu, has sparked concern among public health officials. In the United States, the virus has been detected in dairy cows for the first time, with four dairy workers also testing positive.

A particularly virulent strain of the H5N1 virus has been circulating globally in animals since 2020, causing widespread deaths in commercial poultry and sporadic infections in various species, including alpacas and house cats.

Different bird flu strains have been found in humans in Australia and Mexico, while various H5 subtypes are also present worldwide in both animals and humans, including countries such as China and Cambodia.

Most human cases reported exposure to poultry, live poultry markets, or dairy cattle prior to infection. However, scientists are concerned about the potential for the virus to mutate and become more easily transmissible from person to person, which could lead to a pandemic. The World Health Organization (WHO) currently assesses the risk to people as low.

Below are details about occurrences of different types of bird flu virus detected in humans this year.

The first cases of infected dairy cattle were identified in Texas in March and have since spread to dairy herds in 12 states. The U.S. Department of Agriculture has confirmed that the virus detected in cows is the same H5N1 strain affecting wild birds and commercial poultry flocks. Dairy workers who have tested positive for the virus this year have experienced mild symptoms such as conjunctivitis, also known as pink eye.

The H5N1 virus found in the United States belongs to the clade 2.3.4.4b, genotype B3.13, a genotype detected solely in North America, according to a scientific report by the European Food Safety Agency (EFSA).

The WHO reported on June 5 that a resident of Mexico died from the first known cases of H5N2 avian influenza in humans. While the Mexican government stated that chronic illness, rather than bird flu, was the cause of death, the individual had no known exposure to animals.

On June 7, the WHO reported that a child with H5N1 bird flu, who had traveled to Kolkata, India, had been identified in Australia. Genetic sequencing indicated the virus was an H5N1 subtype and part of a strain circulating in Southeast Asia, previously detected in human infections and poultry.

Australia is separately dealing with three outbreaks of different strains of the virus on poultry farms – H7N3, H7N8, and H7N9 – which authorities believe likely arrived on farms via wild birds.

On June 11, the WHO reported a human infection caused by the H9N2 subtype in a four-year-old child in the eastern Indian state of West Bengal. This was the second human infection of H9N2 bird flu from India, following a case in 2019. While the H9N2 virus typically causes mild illness, the UN agency noted that sporadic human cases could occur, as it is one of the most prevalent avian influenza viruses circulating in poultry across different regions.

Vietnam reported in March that a 21-year-old student had died from H5N1 bird flu. The student had no underlying health conditions but had been exposed to wild birds from hunting a couple of weeks before the onset of symptoms. No contact with dead or sick poultry was reported at the time.

Vietnam also reported an outbreak of H9N2 in a 37-year-old man, according to EFSA.

As of June 20, Vietnam and its neighbor, Cambodia, have reported five human cases of H5N1.

China has detected human cases caused by the H5N6, H9N2, and H10N3 strains this year, including two fatal H5N6 cases in the Fujian province. EFSA reported that both of those cases involved exposure to backyard poultry before the onset of symptoms.

The case of H10N3 avian influenza was the third ever reported globally.

On July 4, the World Organization for Animal Health reported an outbreak of highly pathogenic H7N5 bird flu on a farm in the western part of Germany, near the border with the Netherlands. It was the first outbreak of H7N5 anywhere on WOAH’s public records.

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