A new strain of bird
flu that is causing a deadly outbreak among people in China is a threat to
world health and should be taken seriously, scientists said on Wednesday.
The H7N9 strain has
killed 24 people and infected more than 125, according to the Geneva-based
World Health Organization (WHO), which has described it as "one of the
most lethal'' flu viruses.
The high mortality
rate, together with relatively large numbers of cases in a short period and the
possibility it might acquire the ability to transmit between people, make H7N9
a pandemic risk, experts said.
“The WHO considers this
a serious threat,” said John McCauley, director of the WHO Collaborating Center
for Influenza at Britain's National Institute for Medical Research.
Speaking at a briefing
in London, experts in virology said initial studies suggest the virus has
several worrisome characteristics, including two genetic mutations that make it
more likely to eventually spread from person to person.
“The longer the virus
is unchecked in circulation, the higher the probability that this virus will
start transmitting from person to person,” Colin Butte, an expert in avian
viruses at Britain's Pirbright Institute, said.
Of the some 125 people
infected with H7N9 so far, around 20 percent have died, approximately 20
percent have recovered and the remainder are still sick. The infection can lead
to severe pneumonia, blood poisoning and organ failure.
“”This is a very, very
serious disease in those who have been infected. So if this were to become more
widespread it would be an extraordinarily devastating outbreak,” Peter
Openshaw, director of the center for respiratory infection at Imperial College
London, told the briefing.
Scientists who have
analyzed genetic sequence data from samples from three H7N9 victims say the
strain is a so-called “triple reassortant” virus with a mixture of genes from
three other flu strains found in birds in Asia.
Recent pandemic
viruses, including the H1N1 “swine flu” of 2009/2010, have been mixtures of
mammal and bird flu - hybrids that are likely to be milder because mammalian
flu tends to make people less severely ill than bird flu.
Pure bird-flu strains,
such as the new H7N9 strain and the H5N1 flu, which has killed about 371 of 622
the people it has infected since 2003, are generally more deadly for people.
Human cases of the H7N9
flu have been found in several new parts of China in recent days and have now
been recorded in all of its provinces.
Last week a man in
Taiwan became the first case of the flu outside mainland China, though he was
infected while travelling there. The H7N9 strain was unknown in humans until it
was identified in sick people in China in March.
Scientists say it is
jumping from birds - most probably chickens - to people, and there is no
evidence yet of the virus passing from person to person.
Jeremy Farrar, a
leading expert on infectious diseases and director of Oxford University's
research unit in Vietnam, said the age range of those infected so far stretched
from toddlers to people in their late 80s - a range that appeared to confirm
the virus is completely new to the human population.
“That suggests there
truly is no immunity across all ages, and that as humans we have not seen this
virus before,” he said. “The response has to be calm and measured, but it
cannot be taken lightly,” he said.
Sources :
http://www.voanews.com/content/scientists-new-bird-flu-poses-serious-threat/1652860.html
No comments:
Post a Comment