HANGZHOU -- Chinese disease control experts said that the public should stay on alert for H7N9 avian flu, which has caused at least nine deaths this year.

H7N9 has entered its peak season and direct contact with live poultry remains the main source of infection, said a statement by Zhejiang provincial disease control and prevention center Tuesday.

Genetic analysis showed that there had been no mutations of the virus, but since late Autumn last year the epidemic had been reported in a wide range of areas, it said.

The virus was more active in 2016 than in the same seasons in previous years. A total of 44 cases were reported last year in Zhejiang, causing two deaths.

H7N9 is a bird flu strain first reported to have infected humans in March 2013 in China. It is most likely to strike in winter and spring.

At least nine people died from the virus since the start of this year, according to disease control centers in Henan, Guangdong and Hunan provinces.

On Tuesday, health authorities in Henan province announced two deaths from the virus, respectively on Jan 23 and 24. Both patients had worked at restaurants prior to the infections.