Health officials in China reported Tuesday that four more people had developed H7N9 avian influenza, bringing to seven the total number who have been infected with this particular strain, which has never been seen before in humans. So far two men, aged 87 and 27, have died—both in Shanghai.


Although H7N9 has not been reported in people before, the larger H7 family of flu viruses has infected people previously—in the Netherlands, Italy, Canada, the U.S. and England. Those cases were associated with H7 outbreaks in poultry—and seemed to be milder in comparison to the latest cases.

The evidence to date suggests that this particular strain of H7N9 also got its start in poultry. One of the newly affected individuals reportedly was a Nanjing poultry butcher.

Chinese authorities said they had found no bird flu virus among the thousands of dead pigs that mysteriously turned up in tributaries of the Huangpu River near Shanghai in early March. The dead pigs still pose a health risk, particularly since the city of about 24 million people depends on the Huangpu for much of its drinking water.

Authorities have found no evidence of the kind of easy transmission between people that would lead to larger outbreaks. But the fact that most of the people who have fallen ill apparently had no contact with each other suggests that there might be more than one source of infection.

The Hong Kong Health ministry—which is tops at finding and tracking new bird flu cases—is on high alert, checking its animal markets as well as individuals at its border crossings for evidence of fever. You can be sure, I’ll also be keeping a closer eye on the Twitter feeds for two top English-language flu journalists—Helen Branswell of the Canadian Press and Margie Mason of the Associated Press.

Image credit: Gérald Tapp, via Wikimedia Commons, CC-BY-SA-3.0