[A-List] modeling avian flu diffusion

[Autoplectic <autoplectic@xxxxxxxxx>]

<http://society.guardian.co.uk/health/story/0,7890,1542250,00.html>

Flu could infect half world's people in year

WHO in talks to stockpile antiviral drugs in case of global outbreak

Ian Sample, science correspondent
Thursday August 4, 2005
Guardian

An outbreak of flu in rural south-east Asia could spread around the
globe in three months and infect half the world's population within a
year, unless strict measures to contain it are introduced, scientists
said yesterday.

The warning comes from researchers who used computer models to
investigate what would happen if the avian flu virus, which is
currently rife among poultry in areas of China, Cambodia, Thailand and
Vietnam, mutated into a form that spread easily among humans.

Scientists believe it is only a matter of time before the virus, known
as H5N1, mutates to become more infectious to humans, possibly by
swapping genes with the human flu virus.

"This is the event we're all scared might happen at any time," said
Neil Ferguson of Imperial College London and the leading author of the
study. "We'd be faced with an event worse than the 1918 Spanish flu
pandemic."

The avian flu virus has killed more than 50 people in Asia, more than
half of those who have been infected. Almost every death was traced
back to the person coming into contact with infected poultry in the
countryside. The Spanish pandemic of 1918 is believed to have claimed
up to 40 million lives worldwide.

Professor Ferguson's team modelled the spread of a mutated avian flu
virus among 85 million people living in Thailand and a strip of
neighbouring countries. After watching how quickly the virus spread
around the globe, they tested various strategies for containing an
outbreak. "Until now, the idea of stopping an outbreak hadn't been
investigated," he said.

If an outbreak was detected in its infancy, with less than 50 people
infected, models show it could be contained by administering antiviral
drugs to the 20,000 people closest to those infected, the researchers
report in the journal Nature today. Combined with other measures, such
as shutting schools and workplaces, it would take around 60 days to
contain the outbreak, with the number of cases totalling no more than
around 200.

To deal with the worst case scenario of an avian flu outbreak, the
scientists called for an international stockpile of 3m courses of
antiviral drugs to be set up, ready to be deployed anywhere in the
world within a few days of an outbreak being detected.

A spokeswoman for Roche, which manufactures the antiviral drug
Tamiflu, confirmed that the company is in talks with the World Health
Organisation about building a stockpile of the drug, but refused to
give further details. The WHO already has 120,000 courses of Tamiflu,
but with Britain and France each waiting for orders of 15m courses
from Roche, the company will have to decide which takes priority.

Prof Ferguson's research is reported alongside a second study
published online today by the US journal Science, which modelled an
outbreak of flu among half a million people living in Thailand.

Ira Longini and his team at Emory University in Atlanta also found
that antiviral drugs could be used to contain an outbreak by giving
them to healthy people closest to those infected. Flu vaccines, even
relatively poor ones, would also help quash a nascent outbreak, he
said.

According to Professor Longini's model, 100,000 courses of Tamiflu
would be enough to prevent a flu outbreak becoming a pandemic as long
as the virus had a "reproductive number" - the average number of
people each infected person goes on to infect - of no more than 1.6.
Measles, one of the most infectious diseases has a reproductive number
of around 15. Typically, each person infected with flu infects two
others.

Prof Longini said the creation of an international stockpile of drugs
should take precedence over orders from individual countries. "The WHO
should get priority ... and the richer nations should chip in, because
it's in their interests to stop it before it reaches their shores," he
said.

Creation of the stockpile is just the first hurdle. The WHO, in
conjunction with the US Centres for Disease Control and Prevention in
Atlanta, will have to tread carefully with governments to ensure the
policies are adopted and that outbreaks are spotted quickly enough.

A scientist close to the programme said: "The big issue is
surveillance. If these models are right, and there may be problems
with them, the outcome depends on getting an early warning of an
outbreak."

-- 
"I'll judge you all and make damn sure that no-one judges me" [Jethro Tull]