Public health scientists say millions of human deaths in an avian flu outbreak in Southeast Asia could be prevented if authorities rapidly impose quarantines and travel restrictions and widely distribute antiviral medications.
To work, they said such an emergency plan must be enacted within two days and the spread of the virus limited to a few dozen cases, even though communications in much of the region are rudimentary and entire economies and transportation networks could be disrupted.
“Containment is challenging,” said Neil Ferguson of Imperial College in London and lead author of one of a pair of studies examining avian flu control measures. “We just can’t cherry-pick the more easily implemented solutions.”
Since 2002, the virus has swept through poultry populations, killing at least 60 people, most of whom were farmers and poultry workers in Thailand and Vietnam who contracted the illness directly from infected birds.
The virus has been carried as far north as western Siberia by migrating wild birds, which have infected poultry farms there. Authorities have killed millions of birds to stem its spread.
Global outbreak could spread quickly
There are very few cases of the H5N1 influenza virus spreading from person-to-person. But the H5N1 virus is so lethal that a global pandemic could spread quickly and agencies are beginning to develop emergency plans.
According to some predictions, the virus could spread unchecked once as few as 40 people are infected in an untreated community.
Some scientists predict the containment effort probably would be concentrated in poor, hard-to-reach villages in Thailand, Vietnam and other countries. That’s where most of the region’s poultry stocks are located, which serve as a reservoir for the virus.
Others predict it will erupt in an urban setting because flu spreads so quickly and that’s where poultry markets and distribution centers are located.
Either way, as many as 3 million doses of antiviral drugs like Tamiflu could be needed, researchers said.
And, according to a second analysis by researchers in the United States, early intervention is so essential that even prevaccination with a poorly effective vaccine would buy precious time for scientists looking for ways to keep the new flu strain out of southeast Asia’s surging cities — and beyond.
Many unknown factors remain
Public health officials said the British and U.S. studies, based on computer simulations, offer good advice. However, a real outbreak probably would be harder to contain because so many unknown factors remain. They include how contagious the virus will be, how severely ill people get and who is at greatest risk.
“We need to look at these models in a balanced manner,” said Margaret Chan, director of infectious disease surveillance and response at the World Health Organization.
Plus, the models used in both studies assume that drugs would work against the virus.
“It’s possible that we end up with a strain that doesn’t respond to the type of drug stockpiled,” she said.
In the British study, which appears in Thursday’s issue of the journal Nature, Ferguson’s team simulated an outbreak in rural Thailand. Researchers said that to limit the outbreak to 200 cases, the problem would have to be recognized when as few as 30 people were infected. Antiviral drugs would need to be distributed to 20,000 people living in the surrounding area, they said.
Ferguson recommends stockpiling 3 million doses of antiviral, while also closing schools, airports, workplaces and other venues.
In a second paper appearing in Friday’s issue of the journal Science, Ira Longini of Emory University and others report that vaccinating half of an urban population in a city would limit the infection rate to one case for every 1,000 people within two weeks. Currently there is no effective vaccine against H5N1.
Starting with a single infection, Longini simulated the spread of the virus in a population of 500,000 in which individuals mixed in settings such as households, neighborhoods, schools, workplaces, a hospital, markets and a temple.