Friday, January 13, 2006
Associated Press
LONDON — Analysis of samples of the H5N1 bird flu virus from two of
its
victims in Turkey has detected a change in one gene in one of two
samples
tested, but it is too early to tell whether the mutation is important,
the
World Health Organization said Thursday.
The mutation, which allows the virus to bind to a human cell more
easily
than to a bird cell, is a shift in the direction of the virus being
able to
infect people more easily than it does now. However, that does not mean
the
mutation has taken root.
"We assume this could be one small step in the virus' attempt to adapt
to
humans," said WHO virologist Mike Perdue. "But it's only seen in one
isolate
and it's difficult to make sweeping conclusions. We just have to wait
and
see what the rest of the viruses [from Turkey] look like."
Turkey has seen an unusually high number of cases in a short period of
time.
Experts are investigating why.
Health authorities there raised the number of people infected with H5N1
from
15 to 18 on Thursday, after the virus turned up in preliminary tests on
two
people hospitalized in southeastern Turkey and in a lung of an
11-year-old
girl who died last week in the same region.
All the victims are thought to have close contact with infected
poultry.
Samples from several of those cases are being sent to a laboratory in
Britain for analysis.
Perdue said the U.N. health agency is not alarmed by the finding in a
single
virus sample because this exact genetic change has been seen before, in
samples from southern China in 2003, and it had no impact on the course
of
the disease, the behavior of the virus or the pattern of human
infections.
"If we saw it in more than 50 percent of samples, it would suggest the
virus
is really trying to adapt to humans and it would be problematic," he
said.
Even if the mutation is confirmed in more samples, that does not
necessarily
mean it is an important enough change on its own to make the virus
easily
transmissible between humans, Perdue said.
The 1918 flu pandemic, the biggest in recorded history, became a global
killer only after the virus slowly made a series of genetic mutations.
Influenza viruses are notoriously volatile, and experts expect to see
mutations frequently. Many mutations are meaningless, or happen in only
a
minority of the virus samples, but specialists are watching the H5N1
virus
carefully to pick up any important changes as early as possible.
Although nothing can be done to stop the mutations, tracking them is
considered the best way to anticipate the next human flu pandemic.