- WASHINGTON (AP) -- Genetic studies of a bird flu that has killed six people in
Hong Kong show that it has not mutated into a more dangerous virus and
is unlikely to cause a worldwide epidemic.
- Federal experts, however, say there remains
a need for caution. Just to be on the safe side, scientists at the Centers
for Disease Control and Prevention are working on a new vaccine.
- A report on the genetic study of the
bird flu virus appears today in the journal Science.
- ``It is good news for now,'' Dr. Kanta
Subbarao of the CDC flu laboratory in Atlanta said. She said experts, though,
worry that the Hong Kong bird flu still could make genetic changes that
would turn it into a more virulent human killer.
- ``We remain concerned that a reassortment
(genetic change) could occur at any time,'' said Subbarao, the first author
of the study.
- A 25-year-old woman died Wednesday, the
Hong Kong government announced Thursday. She was the sixth person in Hong
Kong killed by the bird flu since the outbreak began in May. At least 12
other people have been infected.
- Subbarao said she and other CDC experts
have not determined how the avian flu virus strain, called H5N1, managed
to infect humans. Usually a bird flu virus will not directly spread to
humans, and the fact that H5N1 made some people sick has alarmed international
flu experts, she said.
- Flu virus genes are highly changeable,
and slightly altered flu strains appear almost annually. Usually, the new
strain resembles previous strains and most humans have some immunity against
- Occasionally, a unique strain develops
that is particularly deadly. Many such flu strains originate in birds,
then spread to swine, which are capable of hosting both the bird flu and
human flu. When the two viruses genetically mix in the pig, the result
can be a totally new flu strain.
- There were fears, said Subbarao, that
this genetic mixing could have happened to H5N1 inside humans who got the
bird flu in Hong Kong. She said a bird flu that acquired internal human
flu genes could be capable of spreading rapidly from person to person.
- ``The human population would have no
immunity, no protection against such a virus,'' said Subbarao. ``The virus
could spread and cause a pandemic (a worldwide epidemic). ... It could
have a very high mortality rate.''
- A unique flu strain in 1918 killed 20
million people worldwide. Smaller outbreaks occurred in 1957 and 1968.
- Subbarao said studies at the CDC found
that the H5N1 that infected 18 people in Hong Kong has not changed genetically.
All of its genes are those of bird flu.
- This means, she said, that H5N1 is not
now highly virulent among humans, boosting confidence that the immediate
human threat is over.
- To contain the virus, health officials
slaughtered more than a million chickens in Hong Kong and blocked importation
of chickens from nearby provinces in China.
- Clearing Hong Kong of live chickens,
said Subbarao, may have ended the outbreak, at least for now.
- ``The slaughter was absolutely essential,''
virus expert Robert Webster of St. Jude Children's Research Hospital said
in Science. ``The big question is whether the stable door was shut in time.''
- Subbarao said no new human case of H5N1
has been recorded since Dec. 28. No cases have been reported outside Hong