University at Buffalo - The State University of New York

Published: May 1, 2003

By JOHN DELLA CONTRADA
Contributing Editor

Though there is much still to learn about the cause and spread of severe acute respiratory syndrome (SARS), a UB virologist says the behavior of other respiratory viruses suggests that SARS could either "collapse" within the next two months or continue into the winter as a flu-like illness of moderate severity.

"It's impossible to predict at this stage where the virus is going," says Ian Hay, professor and chair of the Department of Microbiology in the School of Medicine and Biomedical Sciences, "but as viruses pass through new hosts, they often tend to become less virulent over time and we can hope that this might happen with the SARS virus.

"Also, respiratory virus infections often are more prevalent in the winter months, so SARS could become endemic during those months, much like the flu," he adds.

Coronaviruses have been present for many years in domesticated farm animals and birds, and a human form of the virus is a cause of about a quarter of common colds, Hay says. Humans may have picked up a mutated form of the virus from animals, or a human virus could have mutated into the SARS virus, according to Hay.

"A human coronavirus may have mutated from a disease of the upper respiratory tract into a disease of the lower respiratory tract causing the respiratory problems that have affected SARS sufferers," Hay says.

And it's possible that many people have had the SARS virus without showing symptoms, he adds.

"It's not uncommon for people to be infected with a virus and not show any symptoms," Hay says. "During the polio outbreak, for example, most of the people who were infected had no symptoms. Only a small percentage of people got seriously sick. This is not true of all viruses, but it is more common than not."

Hay speculates that SARS "superspreaders"—those who spread the disease to many people—may have much higher levels of virus in secretions from their respiratory tract than other SARS sufferers. "So when they cough or sneeze, the amount of virus shedding is very high," Hay says.

Another possibility is that superspreaders are infected with a stronger strain of SARS, but Hay doubts the virus has had enough time to produce and select enough relevant mutants at this stage.

"There is so much we don't know about the way viruses grow in individuals," Hay says. "There may, for example, be a genetic component involved in why some people seem to be more susceptible to SARS than others."