Iowa Alumni Magazine | December 2005 | Features

On Wings of Fear

By Tina Owen
"These birds don't worry about a passport or visa."

Mary Gilchrist, 67BA, director of the UI Hygienic Laboratory, is referring to the flocks of wild ducks and geese that migrate from Asia and Russia across the Bering Strait to the United States. Gilchrist and other public health officials worry about what these feathered visitors could carry with them on their long, cold journey: the avian flu virus that poses a potentially dire threat to human health.

Many wild birds are natural carriers of the H5N1 strain of avian influenza virus. With the discovery that the pathogens can hop from birds to humans and create a much deadlier illness—as in the 1918 flu pandemic that killed millions of people worldwide—researchers are understandably concerned.

Worries about a pandemic reached a new high this past fall, when the media reported widespread infection of bird flocks across Asia and Europe. Some 130 humans have succumbed to the disease—about half with fatal results. "Most of these people had close contact with domestic poultry but there are some indications of human to human transmission, which is a cause for concern," says Gilchrist. "Whereas the normal influenza virus kills about 36,000 predominantly young or elderly Americans every year, the highly pathogenic bird flu strain would be much more dangerous if it were to become easily transmissible from human to human."

More so than other viruses, influenza changes and mutates frequently. Depending on the magnitude of the changes, scientists refer to "drifts" or "shifts" in the virus. A drift happens when the virus alters slightly, whereas a shift signifies a much more dramatic change, such as the jump from H1N1 virus prevalent at the beginning of the 20th century to the H2N2 virus that killed some 500,000 people worldwide during the 1957 pandemic. "New strains that haven't been experienced by humans before are bound to be the most dangerous," says Gilchrist. Almost no one has been exposed to the current H5N1 bird flu virus and therefore there's no immunity. It's a substantial concern."

The vaccines that are used for protection from influenza each year don't work against H5N1 or other new viruses. "Lack of the public's inerest in vaccination for 'garden variety' influenza has caused the industry to avoid innovation of newer, faster methods of vaccine production," says Gilchrist. "The U.S. government is contracting production of vaccines against H5N1 but the production is slow."

An optimist, Gilchrist sees the current situation as an opportunity to prepare for the inevitable pandemic, whether it is due to H5N1 or another influenza strain. "Never before in history have we had such a warning about an infectious disease," she says. "We're in a race with the virus and we must invest our efforts. Let's not ignore the warnings as we did for Pearl Harbor."

As well as changes in the virus, human behavior also contributes to the severity of an influenza outbreak. Influenza pandemics in the 17th and 18th centuries were naturally limited by the fact that humans traveled less then. With our modern global transport systems, an infected person can journey from one continent to another in a matter of hours. Pre-flight screenings to identify unhealthy passengers offer little protection, as signs of infection may not show up until long after the passengers disembark.

"In 1900, a plague outbreak in the U.S. started with a rat on a ship that docked in San Francisco harbor," notes Gilchrist. "Now, planes are bringing plagues."

Unsuspecting airline passengers carried the viruses that caused several cases of measles in Iowa in 2004 and the Severe Acute Respiratory Syndrome (SARS) outbreak in Toronto in 2003. "In the case of a new pandemic, not only would we face a new virus that could become easily transmissible, but our modern transit system could enable such transmission to happen rapidly," says Gilchrist. "An estimated 170-340 million people could die if we have a flu pandemic."