April 3, 2006

Travel bans won’t stop bird flu: study

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - Travel restrictions and school
closures will do little to stop a pandemic of bird flu from
marching across the United States, but they may slow it enough
to distribute drugs and vaccines, according to a new study
published on Monday.

"It's probably not going to be practical to contain a
potential pandemic by merely trying to limit contact between
people such as by travel restrictions, quarantine or even
closing schools," said Timothy Germann of Los Alamos National
Laboratory in New Mexico, who worked on the report.

"But we find that these measures are useful in buying time
to produce and distribute sufficient quantities of vaccine and
antiviral drugs."

Their study, published in the Proceedings of the National
Academy of Sciences, supports the approach being pursued by the
U.S. government and recommended by the World Health
Organization for preparing for a possible influenza pandemic.

"Our model suggests that the rapid production and
distribution of vaccines, even if poorly matched to circulating
strains, could significantly slow disease spread and limit the
number ill to less than 10 percent of the population,
particularly if children are preferentially vaccinated," the
team at the U.S. Department of Energy's Los Alamos National
Laboratory and the University of Washington wrote.

Catherine Macken of Los Alamos said the computer model used
in the study provided a surprising finding -- using a weak
vaccine in many people would be better than trying to vaccinate
a smaller number of people with a more effective dose.

"If you reduce somewhat the length of time that someone is
infective ... you end up getting a significant impact," Macken
said in a telephone interview.

"You might be better off vaccinating twice as many people,
getting a lower level of protection, but still getting an
improvement in susceptibility."

No flu vaccine is perfect and experts have been uncertain
which approach would work better.


Using several million doses of drugs like Roche AG's
Tamiflu and GlaxoSmithKline's Relenza that can help prevent
influenza infection could also help, the researchers said.

The H5N1 strain of avian influenza is spreading rapidly in
birds around the world and experts believe it will soon be
found everywhere. It rarely infects people, but has sickened
190 people and killed 107 of them, according to WHO.

If the virus mutates slightly and gains the ability to pass
from person to person easily, it is likely to become much less
fatal but could cause a pandemic.

Scientists are racing to make a vaccine against it and
governments are trying to stockpile drugs that can prevent and
treat the infection, but supplies are low.

In the meantime, health experts are trying to work out the
best way to deal with a pandemic if it comes, and want to know
if schools, businesses and transportation should be closed to
try to slow the flu's spread.

The team at Los Alamos and the University of Washington ran
a complex computer simulation of what the spread of bird flu
might look like in the United States. They say their findings
would hold for any highly mobile society.

"In the event that a pandemic influenza virus does reach
the U.S., according to our results, the U.S. population could
begin to experience a nation-wide pandemic within 1 month of
the earliest introductions," the researchers wrote.

The model assumes that about a third of the population
would become infected -- the rate seen in the past two
pandemics, in 1957 and 1968.

They included several circumstances for people to meet and
potentially pass the virus along, including households,
neighborhoods, preschools, playgroups, schools, shops and work.