BEIJING » The toll from China’s new strain of bird flu climbed to seven on Monday (Sunday in Hawaii) with the death of a 64-year-old retiree in Shanghai and the number of cases spread to 24, but officials expressed confidence the outbreak could be contained.

The World Health Organization’s representative for China, Michael O’Leary, said the flu known as H7N9 did not appear to be transmitted between humans, which should limit its spread.

“The recent reports from China are the first cases of human infection with H7N9 viruses. Although we do not yet know the source of infection, at this time there is no evidence of sustained human-to-human transmission,” O’Leary said at a joint press conference with Chinese health officials.

The international agency also offered to send a team of researchers to help the Chinese.

The cases so far have all come from Shanghai and four surrounding provinces. Most have involved people who had direct contact with infected poultry. However, there might be milder cases of the illness that have gone undetected, acknowledged Liang Wannian, director of the Chinese health agency’s H7N9 flu prevention and control office.

What has frightened researchers is the speed with which the confirmed victims sickened and died. The 64-year-old man who was the latest victim sought medical treatment for a pneumonia-like illness on Wednesday, was admitted to the hospital on Sunday and died a few hours later. However, a 4-year-old boy from Shanghai was reported to have made a full recovery.

Shanghai residents appeared to be avoiding chicken restaurants. Even the ever-popular Kentucky Fried Chicken outlets were emptier than usual. A panic broke out Saturday when passengers on one Shanghai subway line discovered a live chicken left behind in a bag.

As of Saturday night, nearly 100,000 birds had been killed and their bodies cremated to prevent the spread of the illness, according to the state media.

All live poultry markets have been closed and sales of live birds banned. Poultry sales have been banned as well in nearby Nanjing and other cities. Aviaries at zoos have been temporarily closed.

Zhong Nanshan, a Guangzhou-based expert on respiratory diseases, also called for screening of wild birds that could be carrying the disease.

“Analysis shows that the H7N9 virus comes from fowl, including poultry, wild fowl, migrating birds and pigeons,” Zhong said on state television on Sunday.

The Chinese public remains wary of government disease response measures after scandals involving government cover-ups during the SARS outbreak in 2002-03. This time around, there was a delay of several weeks, but government officials say that was because of uncertainty of the diagnosis.

The H7N9 strain was previously recognized, but infected only birds.

Last month, thousands of dead pigs were found washed up along the banks of Shanghai’s main waterway, a phenomenon that has yet to be fully explained. Government assurances that the flu is not related to the pigs have been received with skepticism.

John Hannon of the Beijing bureau contributed to this report.