Avian Influenza Cluster in Cambodia

There won’t be a regular “Clear and Present Thinking” update this week. I am just providing a brief note that the Cambodian government today announced the death of a 12 year old from HPA1/H5N1 (highly pathogenic H5N1 bird flu). That is the country’s first death in a decade from this virus. While not that unusual in itself, what is concerning is the finding that 12 other people in the village are infected, and the Cambodian press is reporting a “high number of dead animals” around the village. The first critical question to be answered is, will they find any evidence for person to person transmission? This is a large cluster of infected people, but they may live in an environment where many have close contact with infected birds during this world- wide avian influenza pandemic. The question of human to human transmission may be difficult to answer in a setting like a rural agrarian village. The other question concerns the “large number of dead animals around the village”. If they are all birds that’s not really concerning under the current circumstances. If the dead animals are mammalian species that’s a different story. H5N1 is currently causing a mass die-off event of birds around the world, but has not been deemed to have a high potential for human pandemic spread. This virus has spread to a number of mammalian species as was recently widely reported, and that appears to be the result of a clade of the H5N1 having acquired a mutation allowing it to attach to mammalian cell receptors in the airway. Should the virus acquire the ability to spread from mammal to mammal (and not just be a dead end transmission from bird to another animal) then progressive adaptation to mammalian physiology, including humans, becomes more likely.

It is certainly reassuring how rapidly this event has been reported by the Cambodian authorities, and we look forward to further clarification as the data becomes available.