Reacción a "Man infected with H5N2 avian influenza virus dies in Mexico"

At a time when many people’s attention has been focused on H5N1 influenza in cattle in the USA, this case is a reminder that there are lots of other influenza viruses out there that also have the potential to infect humans. However, it is important to stress that at the moment this case was a sad but isolated incident. At the moment there is no suggestion that this particular influenza virus has spread any further in humans.

Details of the case are still emerging, but at the moment we know that the virus was an H5N2 influenza virus, making it distinct from the H5N1 influenza viruses that are currently spreading in cattle in the USA and in birds worldwide. Influenza viruses can exchange genes with each other, but whether or not that’s happened here will only become clear when viral sequence data are available. For now, we know that there have been recent outbreaks of H5N2 influenza viruses in poultry in Mexico, suggesting that this case may have been related to one of those.

Exactly how the person became infected is not yet known, but although there was no record of contact with poultry this sounds like it was most likely a “spillover” infection, in which a virus that was adapted to one species of host manages to infect a member of another species (in this case a human), but is not able to transmit any further. It’s probably significant that the person in question had multiple underlying health conditions, and had been very unwell for some time before showing signs of this infection. This is likely to have made it easier for a virus that normally grows in birds to infect them, and unfortunately it may also led to them experiencing severe disease when they became unwell. It’s not yet clear if the virus had to undergo any particular changes to replicate in this person (something that would definitely be required if it was to spread further in humans). This should become clearer if the virus’ genes can be sequenced and compared to other similar viruses.

At the moment surveillance is taking place, including testing people who may have been exposed to the virus but fought off the infection to see if they show any signs of an immune response. If there are more human infections with this virus it would become of wider concern, but for now it is a very sad but isolated case.