A 59-year-old man in Mexico City has died after contracting a subtype of bird flu, the World Health Organization (WHO) reported. The man, who had prior health complications, succumbed to the virus on April 24.
He developed symptoms including fever, shortness of breath, diarrhoea, nausea, and general discomfort. This marks the first laboratory-confirmed human case of infection with an influenza A (H5N2) virus globally, as well as the first avian H5 virus infection reported in Mexico.
The source of exposure to the virus remains unknown, although A (H5N2) viruses have been reported in poultry in Mexico. Despite this, the WHO has stated that the current risk to the general population posed by this virus is low.
The patient had no history of exposure to poultry or other animals but had multiple underlying medical conditions and was bedridden for three weeks prior to the onset of acute symptoms.
The WHO has been unable to establish whether this human case is related to recent poultry outbreaks. In March 2024, a high pathogenicity avian influenza A(H5N2) outbreak was detected in a backyard poultry farm in Michoacan, which borders the State of Mexico where the patient resided. Additionally, low pathogenicity avian influenza (LPAI) A(H5N2) outbreaks were identified in poultry in Texcoco and Temascalapa in the State of Mexico in March and April 2024. However, there has been no confirmation linking this human case to these outbreaks.
This case comes on the heels of other avian influenza concerns globally. In Australia, the first human case of A (H5N1) infection was reported in May, though there were no signs of transmission. Several outbreaks of the H7 HPAI strain were confirmed at poultry farms in Victoria.
Meanwhile, in the US, the H5N1 strain, first reported in 2022, has spread to three farmworkers in Texas and Michigan. According to the US Centers for Disease Control and Prevention (CDC), there is no evidence of human-to-human transmission, and the risk to the general public remains low.
Dr. John Brownstein, an epidemiologist at Boston Children's Hospital, explained that while both H5N2 and H5N1 belong to the same family of influenza A viruses, H5N1 has been known to infect humans for years. This is the first-ever reported case of H5N2 in humans.
"The good news is that neither H5N2 nor H5N1 have demonstrated human-to-human transmission so far. However, this first case is a wake-up call. It reminds us that influenza viruses can evolve, and continued surveillance of these viruses in both animals and humans is crucial," he told a News Agency.
Animal influenza viruses typically circulate in animals but can also infect humans, primarily through direct contact with infected animals or contaminated environments. Human infections with avian influenza viruses can cause mild to severe respiratory illnesses and can be fatal.
Other symptoms such as conjunctivitis, gastrointestinal issues, encephalitis, and encephalopathy have also been reported. Laboratory tests are necessary to diagnose human infections with influenza, according to the WHO.
As the global health community monitors these developments, the case in Mexico underscores the importance of ongoing vigilance and preparedness to address potential outbreaks of avian influenza in humans.
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