The first instance of exposure of humans to H5N2 was in 2006 when Japan's Health Ministry said that poultry farm workers in Ibaraki may have been exposed to H5N2 and was determined that their H5N2 antibody titers after the outbreak were significantly higher than those collected before the outbreak.
On 5 June 2024, the World Health Organization recognised the first laboratory-confirmed case of H5N2 in a human in Mexico in a patient who died but the infected individual had multiple pre-existing illnesses but had no history of exposure to poultry.
WHO said that A(H5N2) viruses have been found in poultry in Mexico, even though the origin of this particular infection is unknown. This case is the first-ever laboratory-confirmed case of influenza A(H5N2) virus infection in humans globally, as well as the first-ever case of H5 virus infection in birds recorded in Mexico.
What is H5N2?
H5 N2 is a subtype of the species Influenzavirus A (avian influenza virus or bird flu virus) according to Dr Tushar Tayal, Lead Consultant, Department of Internal Medicine, CK Birla Hospital, Gurugram. The subtype infects a wide variety of birds.
Symptoms of H5N2
H5N2 is not known to frequently infect humans, however, it can potentially mutate and become infective and would cause the following symptoms such as fever, cough, sore throat, muscle aches, conjunctivitis, diarrhoea, nausea, vomiting and, in severe cases, breathing problems and pneumonia that may be fatal.
How fatal is bird flu?
Dr Neha Rastogi Panda, Consultant-Infectious Diseases, Fortis Memorial Research Institute, Gurugram, said, "Viruses causing bird flu are comparatively less infectious. People can become infected by viruses that are normally limited to birds in specific situations. The disease is not airborne; instead, it spreads through the bodily fluids and excrement of birds. Sixty per cent of instances of viral pneumonia are expected to result from this virus transferring from birds to humans. These viruses undergo particular genetic alterations that make them pathogenic. Furthermore, the virus can merge with human influenza viruses to produce extremely dangerous new genomes. This virus may cause mild to severe infections in the respiratory tract which might prove to be fatal."
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