(Updated @ 1:55 pm CT)
At least 11 human cases of H7N9 influenza have been confirmed in China, although to date there is no evidence of human-to-human transmission, according to the World Health Organization.
The first known human cases of H7N9 infection were reported in China on March 31, which included 2 fatal cases in Shanghai caused by pneumonia associated with infection and a third case involving a patient who was hospitalized in Anhui province. Since then, 4 additional cases in nearby Jiangsu province have been confirmed by laboratory tests, according to a WHO statement on April 3. On April 4, WHO announced 4 more laboratory confirmed cases, including 3 deaths. One of the deaths occurred in a man from Shanghai; the other cases were all patients from nearby Zhejiang province.
So far, WHO said there is no evidence of human-to-human transmission, which would be necessary for a pandemic to occur. The agency said that it and authorities in China are closely monitoring 400 individuals who were in close contact with the case patients, and an investigation is under way to determine the cause of 2 cases of pneumonia, 1 fatal, that occurred in relatives of one of the patients from Shanghai.
It is unclear how the patients became infected. In another WHO statement released yesterday, the organization noted that some of the individuals who were infected had contact with animals. Although a clear animal source of infection had not yet been identified and confirmed by WHO at press time, Chinese authorities were presuming an avian source because H7 strains of influenza have previously been isolated from birds.
Genetic analysis of the strain infecting the Chinese individuals suggests that it did indeed evolve from influenza viruses in birds. However, there were signs that this strain has adapted to infect mammals and is able to bind to mammalian cells and grow at body temperatures typical of humans, which are lower than those found in birds.
To prevent the spread of H7N9 virus or other infectious agents, WHO suggests that individuals continue to use good hygiene practices, such as hand-washing and carefully handling and thoroughly cooking raw meat.