New Strain of Avian Flu in China — Update

To date, Chinese authorities have reported a total of 38 patients with influenza A (H7N9) virus in different cities in China. There have been 10 deaths so far and 19 of the 38 patients are in critical condition. Nine of the cases have been mild. The fact that some cases have been mild may mean that there are more cases in the population who had very mild infections that did not seek medical care, and so were not reported as they did not seek medical care. More than 760 close contacts of the confirmed cases are being closely monitored with no signs of illness. So far there is no evidence of person-to-person spread of this virus.

Scientists urgently want to find out how this virus is infecting people since some patients might have gotten it from poultry or other animals just before falling ill, but others had not. The virus has been found in chickens, pigeons and ducks in live poultry markets in Shanghai and Hangzhou. Tens of thousands of birds have been culled and poultry markets have been shut down in Shanghai, Nanjing and Hangzhou.

Scientists are looking at the genes of the new virus found in the birds to see how similar they are to the viruses found in the patients. Researchers know that H7 flu viruses mainly infect wild birds such as ducks, geese, waders, and gulls, and that they occasionally jump into poultry flocks. But this H7N9 virus has not yet been detected in wild birds in the area. Wherever the virus originated, a crucial question is whether it could become established in poultry, creating a reservoir that might lead to continued, sporadic human infections. H7N9 does not cause serious bird disease, greatly complicating efforts to find how far it has spread and how to control it.

There is some concern that genetic analysis shows that this virus already has 3 of the 5 mutations needed to make it transmissible from person to person. Whether it acquires the additional mutations is anybody’s guess at present. It is too early to predict how events will unfold.

The World Health Organization is monitoring the situation closely and does not recommend any travel restrictions at this time. Travellers should exercise caution, however, and avoid live poultry markets. Frequent hand washing reduces the risk of infection with any influenza virus.