Cases of H5N1 avian flu have been surging in Egypt since the fall. Egypt has now passed Indonesia as the country with the most human cases in total since the virus was first found in Hong Kong almost 20 years ago.
About a third of the 336 cases Egypt has reported to the World Health Organization since 2006 have been fatal. H5N1 avian flu still has killed more people in Indonesia.
Despite the sudden unexplained increase — Egypt has officially reported 125 cases since January — the World Health Organization said the country’s “current risk status” has not changed.
Nearly all cases still appear to involve contact with poultry; the disease has long been endemic in birds throughout Egypt, where many households have small poultry flocks. Transmission from birds to humans continues to be sporadic, the W.H.O. said.
Virologists have long feared that the highly lethal virus will mutate to become more transmissible among humans, but it is not clear exactly which mutations would do that.
A study by Japanese and Egyptian scientists published last week in mBio, and noted by the University of Minnesota’s Center for Infectious Disease Research and Policy, looked at viral genetic sequences found in Egyptian H5N1 victims and the effects of 59 mutations detected in them.
When replicated in the laboratory, some of those mutations appeared to make it easier for the virus to attach to human airways cells; other mutations made the virus better at reproducing there.
That means if the virus circulating in Egyptian birds infects enough human victims, “it could rapidly adapt to growth in the human airway microenvironment,” the authors of the new study concluded.