Bird Flu in Asia--Looming Implications for Humans

By Michael T. Osterholm, Ph.D, M.P.H.

Well over a hundred million chickens and ducks across Asia have died of or been killed to contain the spread of avian influenza, also known as bird flu, in the past year. This is of no concern to us, right? Wrong.

Flu comes in three types—A, B, and C. We humans can get all three. Birds get only type A, for which wild birds serve as the natural hosts. Serious epidemics in humans and birds have been of type A. Subtypes of flu are named according to the exact combination of two proteins on the surface of the virus. For example, the type currently circulating in birds in Asia is called influenza A (H5N1). New flu strains emerge, evolve, and replace old strains continuously, making influenza a complex and dangerous disease.

Avian flu commonly spreads from wild birds to domesticated poultry. The current outbreak of H5N1, however, has seen an historically unprecedented rate of spread, affecting nine Asian countries over the past year, and has been particularly lethal. This has had huge economic implications in Asia and elsewhere, but it has even larger implications for human health worldwide.

H5N1 flu has already jumped from birds to a number of mammals in Asia, including cats, leopards, tigers, and pigs. Most important, it has also been confirmed in 44 humans to date, 32 of whom have died of the disease. In the large majority of the human cases, the disease was caught directly from diseased birds.

The big concern currently is that H5N1 flu will evolve to a form that is easily transmitted among humans, who have no immunity to it. It is really not a question of if, but of when, this will occur. With global travel, it is easy to see how quickly a contagious disease can spread across the world. In other words, H5N1 could easily cause the next influenza pandemic, meaning a global epidemic of a new strain.

Flu pandemics have occurred throughout history with some regularity. The most serious of the 20th century was the Spanish flu of 1918-19 (H1N1), which infected over 200 million people worldwide and killed 40 million. U.S. and international public health agencies have been planning for the next flu pandemic, but their concern and efforts have been accelerated greatly by the current situation in Asia.

A vaccine for humans against H5N1 flu is in development and is expected to be available for clinical trials early next year. No one knows, though, how fast H5N1 will evolve, and there is no guarantee that the vaccine now in development will be effective against the exact strain that emerges to infect humans in large numbers.

The current shortage of human flu vaccine in this country is bringing to light some of the severe limitations in our vaccine production and distribution systems. Public health workers have been caught off guard, and consumers have been upset with the vaccine shortages. Imagine the serious problems and the resulting hysteria that are likely with an H5N1 pandemic.

We are indeed in a race to develop vaccine for H5N1, to significantly increase our international production capabilities, and to greatly improve our distribution systems worldwide before the virus outsmarts us. Stay tuned, and stay informed.

Michael Osterholm is director of the Center for Infectious Disease Research and Policy (CIDRAP), associate director of the Department of Homeland Security's National Center for Food Protection and Defense(NCFPD), and a professor in the School of Public Health, University of Minnesota. This column is an educational service of the University of Minnesota. Advice presented should not take the place of an examination by a health-care professional. For more health-related information, go to http://www.healthtalk.umn.edu/