GENEVA — A third person has died of a new strain of bird flu in eastern China, as cases of the deadly virus were reported in a fourth location.
Two people in Hangzhou city were infected with the H7N9 strain of avian influenza, one of whom died, China’s official Xinhua News Agency said today. The virus has infected at least nine people and killed three of them since China’s health ministry reported the first cases last month. The other two deaths were in Shanghai. Cases have also been reported in Anhui and Jiangsu provinces.
There’s no evidence of human-to-human transmission of the virus, the World Health Organization said in an April 1 statement. The extent of the outbreak, the source of infection and the mode of transmission are being investigated, and it’s too early to tell whether the cases may signal a pandemic, according to the WHO.
“Until we know what the source of infection is, it’d be premature to say one way or the other,” Gregory Hartl, a WHO spokesman in Geneva, said by phone Wednesay. “We wouldn’t be dealing with a full deck.”
China’s Ministry of Agriculture said that tests have found no H7N9 infections in animals, and that it remains unclear where the virus came from and how it spread, Xinhua reported.
Data from the ministry showed that a total of 25 H7N9 bird flu strains have been detected in wild birds around the world and that the virus had not been found in poultry, according to Xinhua. China is on the flight path of migratory birds, the agency reported, citing the ministry.
Roche Holding’s Tamiflu and GlaxoSmithKline’s Relenza are both effective against the virus, Hartl said.
“There was some initial doubt but those doubts seem to have been put aside after a lot of work done in our collaborating center in Beijing,” he said.
Shanghai issued a level-3 flu alert Tuesday, the second- lowest of four levels, following the deaths of the two men, ages 87 and 27, in China’s financial hub last month. Municipal authorities will strengthen monitoring of influenza and will require daily reporting of pneumonia cases where the causes are unknown, Xu Jianguang, head of Shanghai’s health and family planning commission, said at a briefing Tuesday.
Investigations still haven’t uncovered how the two men contracted the virus, and tests have yet to prove whether it can be transmitted among humans, said Wu Fan, head of the city’s disease control center.
There’s also no evidence that the virus is related to dead pigs found in a Shanghai river last month, according to Wu. More than 11,000 hog carcasses were pulled from the Huangpu river, which supplies about 22 percent of the city’s water, and thousands more were found in neighboring Zhejiang province.
The discovery of the new virus has prompted other cities in the region to intensify checks. Beijing, the Chinese capital, started monitoring for H7N9 influenza, Xinhua reported, while Taiwan’s Central News Agency said March 31 the island is on the alert for the bug. Officials in Hong Kong activated the alert response level, the lowest of three in the island’s pandemic preparedness plan, and advised people to avoid direct contact with birds.
“The mutation potential of the virus is high,” Leung Ting-hung, controller of Hong Kong’s Centre for Health Protection, said in an emailed statement Tuesday.
H7N9 hasn’t previously appeared in humans, the WHO said. The virus’s genetic sequence shows it’s still an avian pathogen and hasn’t mixed with human or pig pathogens, Hartl said. The WHO is looking into whether the virus has evolved to become more of a threat to humans, he said.
The flu pandemics of the past century, including the 1918 Spanish flu that killed as many as 50 million people, have all been triggered by the mixing of human and animal flu viruses to create new pathogens to which people have no pre-existing immunity.
More than 600 people have been infected with the H5N1 bird flu strain since 2003, and almost 60 percent have died, according to the WHO. Most had direct contact with infected poultry, and the virus hasn’t acquired the ability to spread easily between people.
The H1N1 virus responsible for the 2009 swine flu pandemic originated in pigs, then mixed with human and avian viruses, touching off the first global influenza outbreak in more than 40 years and killing about 284,500 people, according to the U.S. Centers for Disease Control and Prevention.