HEALTH & SCIENCE

CLIMATE CHANGE SPURS THREAT OF PLAGUE

JAMES KILNER, REUTERS - Warmer, wetter weather brought on by global
warming could increase outbreaks of the plague, which has killed
millions down the ages and wiped out one third of Europe's population in
the 14th century, academics said. Migratory birds spreading avian flu
from Asia today could also carry the plague bacteria westward from their
source in Central Asia, Nils Stenseth, head of a three-day conference on
the plague and how it spreads, told Reuters on Monday. "Wetter, warmer
weather conditions mean there are likely to be more of the bacteria
around than normal and the chance of it spreading to humans is higher,"
he said. . .

The plague -- caused by the virulent, aggressive and mutating Yersinia
Pestis bacteria -- periodically breaks out in Kazakhstan and other
Central Asian countries and has been carried around the globe by fleas
on the back of rats, birds and in clothing for centuries, Stenseth said.
"If you treat it with antibiotics in a few days it should be all right,
but if you leave it any longer there is a 60 percent chance of death."

http://today.reuters.co.uk/news/newsArticle.aspx?type=scienceNews&storyID=2005-11-14T112352Z_01_DIT440964_RTRIDST_0_SCIENCE-PLAGUE-DC.XML


IN DEPTH LOOK AT THE AVIAN FLU THREAT

W. WAYT GIBBS AND CHRISTINE SOARES, SCIENTIFIC AMERICAN - The most
fundamental thing to understand about serious pandemic influenza is
that, except at a molecular level, the disease bears little resemblance
to the flu that we all get at some time. An influenza pandemic, by
definition, occurs only when the influenza virus mutates into something
dangerously unfamiliar to our immune systems and yet is able to jump
from person to person through a sneeze, cough or touch. . .

Some pandemics are mild. But some are fierce. If the virus replicates
much faster than the immune system learns to defend against it, it will
cause severe and sometimes fatal illness, resulting in a pestilence that
could easily claim more lives in a single year than AIDS has in 25. . .

Our first defense against a new flu is the ability to see it coming. . .

Speed is of the essence when dealing with a fast-acting airborne virus
such as influenza. Authorities probably have no realistic chance of
halting a nascent pandemic unless they can contain it within 30 days.
The clock begins ticking the moment that the first victim of a
pandemic-capable strain becomes contagious. . .

The U.S. has a sophisticated flu surveillance system that funnels
information on hospital visits for influenza-like illness, deaths from
respiratory illness and influenza strains seen in public health
laboratories to the Centers for Disease Control and Prevention in
Atlanta. "But the system is not fast enough to take the isolation or
quarantine action needed to manage avian flu," said Julie L. Gerberding,
the CDC director, at a February conference. "So we have been broadening
our networks of clinicians and veterinarians." . . .

Pandemics of smallpox and polio once ravaged humanity, but widespread
immunization drove those diseases to the brink of extinction.
Unfortunately, that strategy will not work against influenza--at least
not without a major advance in vaccine technology. Indeed, if an
influenza pandemic arrives soon, vaccines against the emergent strain
will be agonizingly slow to arrive and frustratingly short in supply.
Biology, economics and complacency all contribute to the problem.

Many influenza strains circulate at once, and each is constantly
evolving. "The better the match between the vaccine and the disease
virus, the better the immune system can defend against the virus,"
Gellin explains. So every year manufacturers fashion a new vaccine
against the three most threatening strains. Biologists first isolate the
virus and then modify it using a process called reverse genetics to make
a seed virus. In vaccine factories, robots inject the seed virus into
fertilized eggs laid by hens bred under hygienic conditions. The
pathogen replicates wildly inside the eggs.

Vaccine for flu shots is made by chemically dissecting the virus and
extracting the key proteins, called antigens, that stimulate the human
immune system to make the appropriate antibodies. A different kind of
vaccine, one inhaled rather than injected, incorporates live virus that
has been damaged enough that it can infect but not sicken. The process
requires six months to transform viral isolates into initial vials of
vaccine. Because people will have had no prior exposure to a pandemic
strain of influenza, everyone will need two doses: a primer and then a
booster about four weeks later. So even those first in line for vaccines
are unlikely to develop immunity until at least seven or eight months
following the start of a pandemic.

And there will undoubtedly be a line. Total worldwide production of flu
vaccine amounts to roughly 300 million doses a year. Most of that is
made in Europe; only two plants operate in the U.S. Last winter, when
contamination shut down a Chiron facility in Britain, Sanofi Pasteur and
MedImmune pulled out all stops on their American lines--and produced 61
million doses. The CDC recommends annual flu immunization for high-risk
groups that in the U.S. include some 185 million people. . .

The U.S. national vaccine advisory committee recommended in July that
the first shots to roll off the lines should go to key government
leaders, medical caregivers, workers in flu vaccine and drug factories,
pregnant women, and those infants, elderly and ill people who are
already in the high-priority group for annual flu shots. That top tier
includes about 46 million Americans. . .

If two billion become sick, will 10 million die? Or 100 million? Public
health specialists around the world are struggling to quantify the human
toll of a future flu pandemic. Casualty estimates vary so widely because
until it strikes, no one can be certain whether the next pandemic strain
will be mild, like the 1968 virus that some flu researchers call a
"wimp"; moderately severe, like the 1957 pandemic strain; or a
stone-cold killer, like the "Great Influenza" of 1918.

For now, planners are going by rules of thumb: because no one would have
immunity to a new strain, they expect 50 percent of the population to be
infected by the virus. Depending on its virulence, between one third and
two thirds of those people will become sick, yielding a clinical attack
rate of 15 to 35 percent of the whole population. Many governments are
therefore trying to prepare for a middle-ground estimate that 25 percent
of their entire nation will fall ill. . .

Even at the standard dosage, however, treating 25 percent of the U.S.
population would require considerably more Tamiflu, or its equivalent,
than the 22 million treatment courses the U.S. Department of Health and
Human Services planned to stockpile as of September. An advisory
committee has suggested a minimum U.S. stockpile of 40 million treatment
courses (400 million pills). Ninety million courses would be enough for
a third of the population, and 130 million would allow the drugs to also
be used to protect health workers and other essential personnel, the
committee concluded. . .

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