Anatomy of China’s bird flu outbreak so far

Only 4 of the 81 people with confirmed cases of bird flu in China have fully recovered, according to a new study of the outbreak by the New England Journal of Medicine. The report also confirms that human-to-human trasmission of H7N9, which could cause a deadly global pandemic, can’t be ruled out. Here’s a summary of the report.

• The numbers. Between March 25 and April 17, 664 people with pneumonia were tested for H7N9, and 81 patients were confirmed to have the virus. So far, the mortality of H7N9 is 21%, but because many patients are still critically ill, the mortality rate will probably rise. Just four people have been released from the hospital after being diagnosed with bird flu.
• Transmission. 77% of H7N9 patients were recently exposed to animals, mostly chicken and, to a lesser degree, ducks and pigs. Other animals included pigeons, geese, quail, wild birds, pet birds, cats, and dogs. Human-to-human transmission still can’t be ruled out. As of April 17, there are three confirmed “family clusters” of the virus, where several relatives contracted the virus despite not being exposed to poultry. You can see two of the clusters in this chart: