LONDON -- Chinese scientists have for the first time found strong evidence of how humans got infected with a new strain of bird flu: from chickens at a live market.

In a small study of four patients who caught the new H7N9 virus, Chinese scientists compared swabs from birds at live markets in eastern China to virus samples from patients. The scientists found the virus from one patient was nearly identical to one found in a chicken. The research was published online Thursday in the journal Lancet.

Chinese authorities have shut down live poultry markets in many affected regions, which seems to have slowed down the virus. Still, Taiwan reported its first case earlier this week.

So far, H7N9 has infected more than 100 people in China and killed more than 20.