H7N9 is a bird flu strain of the species Influenza virus A ( avian influenza virus or bird flu virus ) .

Avian influenza A H7 viruses normally circulate Dispersal amongst avian populations with some variants known Know to occasionally infect humans .

It is known Know that influenza tends to strike Attack during the winter months , and the second wave , which began Process_start in October , was fanned by a surge in poultry production timed for Chinese New Year feasts that began Process_start at the end of January .

The CDC estimates that the H7N9 virus has the greatest potential compared with other influenza A viruses to cause Causation a pandemic , although the risk is low , because like other type A viruses , it is not easily transmitted between people in its current form .