China has confirmed that an 8-year-old student has been infected with the H5N1 bird flu virus, the country's 18th case.

The girl from Suining, a city in the southwest province of Sichuan, showed symptoms of fever and pneumonia on April 16 and was being treated at a local hospital, the Health Ministry said in a statement posted on its Web site late Thursday.

Click here for FOXNews.com's Bird Flu Center

Investigations show that poultry deaths were reported at her home before she got sick, the ministry said, without giving any more details on the outbreak.

People who came into close contact with the girl, surnamed Sun, have been put under medical observation and none have shown any abnormal symptoms, the ministry said.

Lab tests have confirmed that Sun had been infected with the H5N1 strain of bird flu, which has killed at least 113 people worldwide, most after contact with sick or infected birds. Twelve of China's 18 cases have died.

CountryWatch: China

Health experts have warned that the virus could mutate into a form easily passed between people, potentially sparking a pandemic.

Earlier this week, the ministry criticized some local health authorities for being too slow to report suspicious pneumonia cases — potentially an H5N1 infection — or even hiding some.

The ministry didn't speculate on the reasons behind such actions, although local authorities in China often avoid reporting incidents that could draw official attention and possible criticism or censure.