A global pandemic of bird flu claiming millions of lives could be stopped if governments work together, say experts.
Poultry carry the virus
UK and US teams used computer models to work out the possible scenarios if the virus H5N1 mutated and became capable of spreading from human to human.
The result could be deaths on the scale of the 1918 Spanish flu which claimed between 20 and 40 million lives.
However surveillance, plus targeted use of anti-viral drugs, could halt it, they told Nature and Science journals.
The models used by both teams looked at Thailand, one of the places at highest risk from avian flu.
More than 50 people have died from bird flu in south east Asia since the first human cases were reported in 1997.
At present, H5N1 flu strain poses only a limited threat to humans as it cannot be easily spread from person to person.
But experts fear the strain will might acquire this ability, causing a flu pandemic which could kill as many as 50,000 people in the UK.
Looking at this scenario, Professor Neil Ferguson, from Imperial College London, and his colleagues found two key conditions would have to be met to limit an outbreak of human-transmissible bird flu to fewer than 200 cases.
Firstly, the virus would have to be identified while confined to about 30 people, they told Nature.
In addition, antiviral drugs would have to be distributed rapidly to the 20,000 individuals nearest those infected.
They estimate an international stockpile of three million courses of the treatment would be enough to contain an outbreak.
But it would mean having to deploy the drug anywhere in the world at short notice.
Another team from Emory University in Atlanta, the US, led by Dr Ira Longini, simulated an outbreak in a population of 500,000 in rural Thailand, where people mixed in a variety of settings, including households, schools, workplaces and a hospital.
Provided targeted use of antiviral drugs was adopted within 21 days it would be possible to contain an outbreak, they found, as long as each infected person was not likely to infect more than an average of 1.6 people.
If it was more infective than this, household quarantines would also be necessary, they said.
Computer model map of new cases (red) and where the epidemic has finished (green) 60-90 days after an uncontrolled outbreak
Co-researcher Elizabeth Halloran said: "Our findings indicate that we have reason to be somewhat hopeful.
"If - or, more likely, when - an outbreak occurs in humans, there is a chance of containing it and preventing a pandemic.
She told Science journal early intervention could at least slow the pandemic, helping to reduce mortality until a well-matched vaccine could be produced.
Professor Ferguson said: "It's an enormous undertaking and will require cooperation among governments on a large scale."
The World Health Organization said the models would help to improve pandemic influenza preparedness planning.
A spokesman said: "Several countries have already purchased stockpiles of antiviral drugs and WHO has taken steps to establish an international stockpile.
"National and international stockpiles of antiviral drugs may be an essential component of comprehensive international pandemic preparedness, that also includes vaccine development and disease surveillance."