Genetic factors might influence human bird flu infection: WHO
3/11/2006 15:51
Genetic factors might influence human infection of bird flu, which may
explain why some people get the disease and others don't, and why it remains
rare, the World Health Organization (WHO) said yesterday.
Scientists suspect
some people have "a genetic predisposition" for bird flu infection, and others
don't, the UN agency said in a report, which generalized conclusions of a WHO
expert meeting in September.
The theory is based on data from rare instances
of human-to- human transmission in genetically-related persons.
"This
possibility, if more fully explored, might help explain why human cases are
relatively rare, and why the virus is not spreading easily from animals to
humans or from human to human," the WHO said.
The evidence to the theory is
mainly from a family cluster of cases last May in North Sumatra, Indonesia, when
seven people in an extended family died.
Only blood relatives were infected
in the Karo district of North Sumatra, the largest cluster known to date
worldwide, " despite multiple opportunities for the virus to spread to spouses
or into the general community," the WHO said.
Bird flu has infected 256
people since late 2003, killing 152 of them, according to the WHO.
Although
it remains mainly an animal disease, experts fear the virus could mutate and
spark a human influenza pandemic, which could kill millions.
The present
situation is still serious and the risk that a pandemic virus might emerge is
not likely to diminish in the near future, the agency has warned.
According
to the WHO, the development of a pandemic vaccine has become more difficult
following the divergence of circulating viruses into distinct genetic and
antigenic groups.
"To date, results from clinical trials of candidate
pandemic vaccines have not been promising, as these vaccines confer little
protection across the different genetic groups," it said in the
report.
International standards, or "benchmarks", for evaluating the efficacy
of vaccines are urgently needed, and integrated studies of sera from individuals
being vaccinated in various clinical trials would be equally useful - for
industry as well as for national authorities, it added.
Xinhua News
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