Beijing is closely watching poultry at 900 farms and migratory birds at 287 water areas for possible H7N9 infection.

"All poultry and pig farms have been under quarantine since April 5. Farmers are not allowed out, and other people are not allowed in. Fodder coming from outside the farms must be sterilized," said Yao Jiezhang, director of the emergency department of the city's bureau of agriculture.

He said there are very few free-range poultry farms in Beijing, which makes it easy to quarantine all poultry.