A new study is the first to confirm that the H7N9 bird flu virus is passed
from birds to people. But the study did not find evidence of person-to-person
In the study, Chinese scientists provide details about four cases of human
H7N9 infection in the eastern Zhejiang province. All four patients had been
exposed to poultry, either through their jobs or by visiting poultry
How the study was done
The study authors tested samples taken from 20 chickens, four quails, five
pigeons and 57 ducks at six poultry markets where the patients were likely to
have been. Two of the five pigeons and four of the 20 chickens tested positive
for H7N9, but the virus was not found in any of the ducks or quails tested.
Then researchers analysed the genetic makeup of H7N9 viruses from one of the
patients and one of the chickens and found similarities between the viruses,
confirming that the H7N9 virus can be transmitted from poultry to people,
according to the study published online in The Lancet.
The scientists also tracked 385 family members, co-workers and health care
staff who had unprotected contact with the patients. None of them showed any
symptoms of H7N9 infection over 14 days of follow-up, which suggests that the
virus currently cannot be spread among people.
However, there is evidence that the H7N9 virus has developed some genetic
characteristics that adapt it specifically to infection in mammals. Further
genetic changes might enable the virus to be transmitted from person-to-person,
the researchers noted.
"Overall, the evidence, in terms of epidemiology and virology, suggests that
it is a pure poultry-to-human transmission, and that controlling [the epidemic
in humans] will therefore depend on controlling the epidemic in poultry," study
co-lead author Kwok-Yung Yuen, of the University of Hong Kong, said in a
Lancet news release.
That would include measures such as temporary closure of live bird markets,
comprehensive programmes of surveillance, culling and segregation of poultry
species, and possibly vaccination of poultry.
World Health Organization (WHO) officials said that they are concerned about
the ability of the H7N9 virus to jump from birds to humans and to infect birds
without causing obvious symptoms, according to the Associated
"This is definitely one of the most lethal influenza viruses we have seen so
far," Dr Keiji Fukuda, the top influenza expert at WHO, said during a briefing
in Beijing. However, a large number of milder cases may also be going
undetected, he added. WHO officials investigated the H7N9 cases with Chinese
authorities this week, the AP reported.
More than 100 people in China have been infected with the H7N9 virus, with
most getting seriously sick and more than 20 dying, the AP noted. The
first case in Taiwan was confirmed that a 53-year-old man who became sick after
returning from a visit to the eastern Chinese province of Jiangsu.