AUG. 16, 2005 | Avian flu in Asia may seem a world away, but if history repeats itself, one University of Arkansas for Medical Sciences (UAMS) professor says the emerging disease could lead to the next influenza pandemic.
Aubrey J. Hough, M.D., distinguished professor in the Department of Pathology and associate dean for translational research and special projects in the UAMS College of Medicine, recently shared his concerns about Influenza A (H5N1) with the 27th Annual Family Practice Intensive Review held in June.
“We’re in for a potentially serious problem,” Hough told the doctors as he reviewed what is known about the virus strain. While just more than 100 people have contracted the disease, mostly from direct contact with poultry, it has about a 75 percent mortality rate. Hough said that would make the strain about 30 times more virulent than the flu strain of 1918, when about 675,000 Americans died.
How Influenza Mutates
While H5N1 is referred to in the media as avian flu, Hough said that all influenza A viruses originally come from wild birds. When domestic poultry is housed in close quarters with other livestock, which happens in many Asian markets, viruses can quickly spread from wild birds to poultry and then to pigs. The adaptations of the virus during that progression make it even easier for it to be transmitted to humans, and more importantly, from human to human
The fact that the H5N1 virus now is transmitting directly to humans from poultry is creating concern because influenza viruses typically “drift”, or go through slow, steady mutations and move from birds to pigs to humans. In order to jump directly to humans, the virus may have gone through a “shift” – a sudden change that could indicate that it is extremely adaptable and unpredictable.
Influenza was first described in eastern Asia in the 4th century B.C., about 150 years before the beginning of the construction of the
Soon after coming to
The 1918 Spanish Flu
“October 1918 was the deadliest month in American history,” Hough said, laying out the scenario for the pandemic which killed more people in less time than all the plagues in history. The worldwide pandemic killed as many as 40 million people, including 600,000 in the
While most influenza viruses create typical head and chest congestion, which can last for a week or more, the 1918 virus killed people within hours and included hemorrhagic symptoms. Typical influenza viruses are usually the most deadly to children and the elderly, but the 1918 virus killed mostly healthy people between ages 20 and 40. Older individuals may have had partial immunity from earlier epidemics.
The Significance of the 1918 Influenza Virus Today
Hough said pathologists who have studied the 1918 virus (H2N2) believe it went through an antigenic shift, changing from a typical flu virus that infected mostly children and the elderly earlier that year. The earlier version of the disease may have given those populations antibodies to protect them.
The H5N1 virus also may go through such a shift either in swine or during human passage, and with the global marketplace, once it changes to easily spread from person to person, it could be spread around the world within a few days.
“The conditions for a disaster will then have been created,” Hough said.
Currently there is no vaccine for the H5N1 virus, and Hough said one cannot be sure which viral form to use in vaccine development until that virus actually begins spreading through person to person contact. However, several pharmaceutical companies are already working to develop vaccines based on a form that did transmit from person to person in
Hough chaired the Pathology Department in the UAMS College of Medicine for more than 21 years and served two terms as
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