There are many types influenza in birds. Most aren’t transmitted to humans. Very few are highly lethal in humans. It is therefore noteworthy when a new flu virus transmits to and kills humans. This has just happened in China.
On February 19, 2013 an 87 year old man from Shanghai surnamed Lee became ill after being infected with H7N9. He died on March 4, 2013. Two of his sons became ill with high fever, coughing and pneumonia sometime between February 14 and 24 [hat-tip Pixie]. His 69 year old son recovered but his 55 year old son died. The two sons were not diagnosed with influenza, but it seems likely that they were infected with the same virus as their father. This cluster is consistent with human to human spread of H7N9. Further, the fact that two out of three members of the cluster died suggests that the virus is highly lethal.
On February 27, 2013 a 27 year old man surnamed Wu, also from Shanghai, became ill after being infected with H7N9. He died on March 10, 2013. The death of a 27 year old man is also consistent with the idea that this is a highly lethal virus.
A 35 year old woman from Anhui province became ill with a H7N9 infection on March 9, 2013. She is currently in critical condition.
The onset of symptoms between the first infected and the last reported infection is separated by about 3 weeks suggesting an ongoing source of the virus. At this point, no reservoir for these infections has been discovered. Other deaths due to “mystery” respiratory viruses have been reported despite attempts to cover them up. Whether the latter are related to H7N9 is currently unknown
Shanghai Daily, April 1, 2013