BEIJING, Jan. 28-- Eight new human H7N9 cases were reported in China on Tuesday in three provinces.

The eastern province of Zhejiang reported 4 new cases - a 43-year-old woman in Hangzhou, an 81-year-old man and a 63-year-old woman in Huzhou, and a 57-year-old man in Ningbo City, according to the provincial health and family planning commission.

The new cases brought the number of infections in the province this year to 53. Three more new cases were reported in Shenzhen, Guangdong Province, women aged 43, 41 and 31.

The case of a 53-year-old man was reported in Huai'an City, Jiangsu Province.

H7N9 bird flu has killed 19 in China this year, and the total number of human infections had reached 96 as of Monday, according to the Chinese Center for Disease Control and Prevention.

In November last year, a single inter-human transmission case occurred in Zhejiang. Shortly after a 57-year-old man was hospitalized on Nov. 27, his son-in-law tested positive for the virus. Doctors confirmed that the man had transmitted the flu to his son-in-law who recovered fully.

Li Lanjuan, researcher at the Chinese Academy of Engineering and a specialist in H7N9 prevention, said so far there have not been any cases in which one person transmits the flu to another, and the latter transmits the virus to a third person.

Her team has identified H7N9 virus mutations this year, but the mutations are not large-scale.

"Inter-human transmission is very unlikely," said Li, who added that the virus has not evolved to be extensively drug resistant.

Shu Yuelong, director of the Chinese National Influenza Center, said on Monday that a large-scale H7N9 epidemic is unlikely during the Spring Festival holiday.

With bird flu cases increasing on a daily basis, China has stepped up its vaccine research for H7N9.

Hualan Biological Engineering Inc. said in early January that the H7N9 vaccine developed by its subsidiary, Hualan Biological Bacterin Co., Ltd., had passed an initial examination by the food and drug watchdog in central China's Henan Province.

The vaccine is being handled by the China Food and Drug Administration, but it is still hard to say when the vaccine will be approved for production, according to the Henan Provincial Food and Drug Administration.

Chicken has been a requisite dish on Chinese dining tables for centuries during Spring Festival, which begins this Friday.

Chinese farmers have traditionally raised chickens using free range methods, especially in the countryside, which has been deemed by experts a risk for spreading bird flu.

Live poultry trading has been halted in Hangzhou, Ningbo and Jinhua cities in Zhejiang, which reported largest number of human H7N9 cases. The province has launched emergency surveillance of poultry farms, haunts of migrant birds and parks, in addition to halting the flying of domestic pigeons.