A CNN article has several scenarios thought up an Australian think tank that could occur should the H5N1 virus mutate and cause an outbreak in humans. The worst case scenario would be 142 million deaths worldwide and an economic cost of $4.4 trillion.
The study, prepared for the Sydney, Australia-based Lowy Institute think tank, says there are "enormous uncertainties" about whether a flu pandemic might happen, and where and when it might happen first.
But it says even a mild pandemic could kill 1.4 million people and cost $330 billion.
In its "ultra" or worst-case scenario, Hong Kong's economy is halved, the large-scale collapse of Asian economic activity causes global trade flows to dry up, and money flows out to safe havens in North America and Europe. Deaths could top 28 million in China and 24 million in India.
The Lowy Institute also provided four different scenarios:
Mild, in which the pandemic is similar to the 1968-69 Hong Kong flu;
Moderate, similar to the 1957 Asian flu;
Severe, similar to the 1918-19 Spanish flu (which infected an estimated 1 billion people and claimed as many as 50 million lives);
An "ultra" scenario that is worse than the Spanish flu outbreak.
The two Spanish flu scenarios would also have to take into account the possibility of government's failing in some countries that are overwhelmed by the sick and the dead.