Avian flu continues to pose serious health threats to both human and animal health, especially as the flu season approaches. That's the warning issued Monday by the U.N. Food and Agriculture Organization.
The FAO is calling on the international community to be vigilant for any signs of H5N1 and the new H7N9 avian flu. The former has been around for years, but H7N9 was first reported in China only last April. About 130 human infections were confirmed. Many of those patients had reported contact with poultry. Most had severe respiratory illness. Forty-four people died.
FAO senior animal health officer Ian Douglas saID timing of the warning is important.
"We've had over a decade of experience with H5N1 avian influenza virus and generally speaking we've seen this pattern of increase of incidence of the disease with the coming of cooler weather following summer. The experience with H7N9 version of avian influenza virus is much more limited. But whilst the number of human cases of that infection have declined, there is the possibility that it could reemerge and become a more prevalent infection."
While both strains can jump from poultry to humans, there is a difference between the two.
Douglas said, "The difference perhaps is significant in so far as H7N9 has not been observed to cause much of clinical disease in poultry. And this constitutes a much great challenge because it's not immediately obvious where the birds are infected and therefore, of course, the root of transmission to humans is somewhat more concealed."
The lack of clinical signs makes is difficult to detect.
Health officials are very concerned that avian flu viruses might mutate and allow infections between people, not just between people and poultry. But is there any evidence, so far, that human to human transmission has occurred?
"There have been some suggestions," he said, "of clusters where with very close contact that might have been the case. But of course the possibilities exist for a common exposure to an animal source. Avian influenza viruses can survive for some time outside of the bird or human host and contamination of the environment, at least for a reasonably short period of time, is possible."
Douglas said that avian influenza viruses have the potential to produce a pandemic of human infection.
"In the case of H5N1, fairly rapidly. Over 60 countries in the world reported some cases occurring either in domestic or wild birds. That number is much reduced. Today, however, the infections remain endemic from Egypt across South and Southeast Asia and somewhat entrenched in those populations."
He said it's not clear whether H7N9 would behave the same way, adding there's much to learn about the virus.
Established control methods involve culling - and vaccinations in the case of the H5N1 virus. But the response must also include tracking where the birds came from and their intended destinations - and ensure that poultry markets adhere to sanitation guidelines.