He has written at length in the July/August 2005 issue of Foreign Affairs on the pandemic threat.
According to a recent report by the Center for Infectious Disease Research and Policy, influenza pandemics are the greatest threat of a worldwide infectious disease crisis, and the world needs to be better prepared for the possibility of a pandemic.
Ten influenza pandemics have hit the world over the last 300 years, the two most recent were in 1957-58 and 1968-69, and although several tens of thousands of Americans died in each one, these were considered mild compared to previous ones.
In the 1918-19 pandemic recent analysis estimates that 50 to 100 million people were killed globally. With the present world population at 6.5 billion, more than three times that of 1918, even a "mild" pandemic could kill many millions of people.
Concern has been heightened in recent years of an impending pandemic due to a number of events and factors. H5N1, the avian influenza strain currently circulating in Asia is a major worry. At this point in time scientists are uncertain if, when or where a pandemic will hit.
Osterholm says that in reality a pandemic once underway cannot be avoided, and only its impact can be lessened and although some important preparations are being made, more needs to be done by institutions at many levels of society.
There are apparently three significant types of influenza virus, and influenza type A infects and kills the greatest number of people each year and is the only type that causes pandemics. It usually starts in wild aquatic birds and does not cause illness in these birds, and although it is widely transmitted among them, it does not undergo any significant genetic change.
To date, direct transmission from the birds to humans has not been proven, but when a virus is transmitted from wild birds to domesticated birds such as chickens, it undergoes changes that allow it to infect humans, pigs, and potentially other mammals. Once in the lung cells of a mammalian host, the virus can lead to an entirely new viral strain, capable of sustained human-to-human transmission. If such a virus has not circulated in humans before, the entire population will be susceptible and most people will lack immunity from previous infection.