In June 2024 WHO shared a disease outbreak news update stating that the Mexico International Health Regulations (IHR) National Focal Point (NFP) had reported a confirmed fatal case of human infection with avian influenza A(H5N2) virus. This is the first laboratory-confirmed human case of infection with an influenza A(H5N2) virus reported globally. WHO has assessed the risk to the public as “low”, yet experts have raised concerns about the delay in identification and reporting and unanswered questions.
Case details
The case was a 59-year-old resident of the State of Mexico who had underlying medical conditions and had been bedridden for three weeks prior to the onset of symptoms. The case had no history of exposure to poultry or other animals. On 17th April, the case developed fever, shortness of breath, diarrhoea, nausea, and general malaise before seeking medical attention on 24th April at the National Institute of Respiratory Diseases “Ismael Cosio Villegas”. He died on the same day.
Results from Real-Time Polymerase Chain Reaction (RT-PCR) of a respiratory sample collected at tested on 24th April indicated a non-subtypeable influenza A virus. The sample was sent to the Laboratory of Molecular Biology of Emerging Diseases Centre for Research in Infectious Diseases for sequencing on 8th May. This indicated that the sample was positive for influenza A(H5N2). On 20th May, the sample arrived at Institute of Epidemiological Diagnosis and Reference of the Mexico National Influenza Centre for analysis by RT-PCR. On 22nd May, sample sequencing confirmed that the influenza was A(H5N2). No further cases were reported during the epidemiological investigation.
WHO’s risk assessment and advice
This case is the first laboratory-confirmed human case of infection with an influenza A(H5N2) virus reported globally, and the first A(H5) virus infection in a human reported in Mexico. The health authorities in Mexico continue to investigate the likely source of exposure to the virus; influenza A(H5N2) viruses have been detected in poultry in Mexico recently.
“WHO assess the current risk to the general population posed by this virus to be low.”
The case “does not change” current recommendations on public health measures and surveillance of influenza. However, WHO “continues to stress the importance of global surveillance”. Furthermore, following human exposure, enhanced surveillance “in potentially exposed human populations becomes necessary”.
Despite this response from WHO, experts have expressed concern at the incident. Among them, Dr Rick Bright, immunologist and public health expert, identified “a number of reasons” for caution:
It took over 6 weeks to identify & report this case
Person was bedridden, indicating someone brought virus to hum
No contact w/ poulty (milk?)
Outcome was fatal
Dr Bright described the update as “very sad” but is “truly shocked” at the delay in going public with the case.
“We must do better.”
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