Mexican man dies in first human case of H5N2 bird flu

A man in Mexico has died in what the World Health Organization (WHO) has said is the first lab-confirmed human infection with the H5N2 strain of bird flu.

The 59-year-old Mexico City resident, who had multiple underlying health conditions but no history of exposure to poultry or other animals, was hospitalised on 24th April and died the same day, with the H5N2 infection confirmed and reported to the WHO on 23rd May. It is also the first confirmed case of bird flu in Mexico, according to an agency alert.

“Although the source of exposure to the virus in this case is currently unknown…H5N2 viruses have been reported in poultry in Mexico,” it said. “Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of global surveillance.”

While any human infection caused by a novel influenza A virus subtype is an event that has the potential for high public health impact and must be notified to the WHO, it has assessed the current risk to public health as low.

The man had been bedridden for three weeks for other reasons, before the onset of acute symptoms, including fever, shortness of breath, diarrhoea and general malaise, according to WHO.

Other subtypes of bird flu like H5N1 have spread to humans, but evidence to date suggests that has resulted from exposure to animals or consumption of poorly cooked meat, and there are no documented cases of sustained human-to-human transmission that would be required to cause an outbreak.

In the US, there have been four cases of H5N1 bird flu recorded in humans since the start of April, all in people exposed to cattle or poultry, according to the Centers for Disease Control and Prevention (CDC).

All told, there have been around 900 human cases reported since 2003, and the mortality rate from infection is estimated to be around 50% - which is considerably higher than COVID-19 at around 4% and seasonal flu at 1%.

In the past few years, a highly pathogenic strain of H5N1 has emerged that can jump between 50 animal species, raising the threat level and fears of a potential bird flu epidemic, and the WHO has said the next pandemic is most likely to be caused by an influenza virus.

Yesterday, the US National Institutes of Health (NIH) published its plan (PDF) for advancing H5N1 research and translating new findings into strategies and interventions that can benefit the public.

That includes efforts to increase understanding of the biology of H5N1, particularly mechanisms behind transmission, the development of detection systems and prevention strategies, including vaccines, and finding novel therapies like antiviral agents and antibodies.

CSL Seqirus has an FDA-approved H5N1 vaccine, Audenz, and has been asked by the US government to provide a stockpile of 4.8 million ‘pre-pandemic’ doses matched to the currently circulating strain in the coming months in response to the increase in human cases linked to an outbreak in dairy cattle earlier this year.

There are more than a dozen other H5N1 vaccines in clinical development, including mRNA-based candidates from GSK and Moderna.

Photo by Hana Oliver on Unsplash