The number of bird flu cases in China jumped Sunday to 102, including 20 deaths, the World Health Organization (WHO) said Monday, according to local news agency Xinhua.
It is still not clear how people are becoming infected and the WHO says there is no evidence of the most worrying scenario - sustained transmission between people.
A 36-year-old man from the city of Zaozhuang in Shandong was being treated in hospital, while two more people were infected in eastern Zhejiang province, Xinhua said.
A total of nine people in close contact with the victim in Shandong were under observation but had shown no signs of infection, Xinhua said.
In response to growing concern over the H7N9 virus, 15 global and Chinese health experts are on a mission in Beijing and Shanghai to learn more about the H7N9 bird flu virus that has killed 17 people and sickened 70 others, said Dr. Michael O'Leary, head of WHO's office in China.
O'Leary says a major focus is to learn how the virus infects humans. "The evidence suggests still that poultry is a vehicle for transmission but epidemiologists haven't yet been able to establish a clear and strong link," O'Leary told reporters in Beijing.
Some bird samples have tested positive and China has culled thousands of birds and shut down some live poultry markets. China said earlier this month that it expects to have a vaccine ready in seven months.
