Human Interference May Have Caused SARS To Jump Species

In April 2003, the disease was conclusively identified as a type of coronavirus unlike any other known human or animal virus in the Coronavirus family.

Sanjay Kapil, a Kansas State University associate professor of diagnostic medicine pathobiology, says human interference with domestic and wild animals could be a factor in the development of the disease.

Samples of the pathogens identified in severe acute respiratory syndrome look similar to coronaviruses found in animals. Because the sequences found in human samples are unique, the virus must have changed substantially when it transferred from animals to humans, Kapil said.

Coronaviruses are known to cause severe illness and respiratory disease in animals. They are known primarily for causing the common cold in humans and have the ability to cause moderate upper-respiratory illness.

Kapil, who has studied coronaviruses since 1986, said the severe acute respiratory disease virus probably originated in animals and then jumped species to infect humans.

"When humans interfere with domestic and wild animals, viruses jump species," Kapil said. "Animals play a role in transmission by acting as mixing vessels. AIDS and the West Nile Virus entered the population in the same way."

Coronaviruses can pick up sequences from other sources, which gives them the ability to evolve and recombine with other coronaviruses. By examining the published severe acute respiratory syndrome sequences, the coronavirus can be observed as unlike previously known coronaviruses and possessing genetic sequences from various coronavirus groups, Kapil said.

"Viruses can mutate or spontaneously change, which means that two different coronaviruses can combine to create a third monster," Kapil said. "It is very likely that the virus causing severe acute respiratory syndrome has evolved from a virus that first infected animals and has evolved to a point that it has started creating a strange disease that causes high fever and high mortality in humans."

The number of suspected severe acute respiratory syndrome cases has grown to more than 3,500 and has killed more than 180 people worldwide according to the World Health Organization. Symptoms include high fever, dry cough, difficulty breathing and shortness of breath. The disease is believed to have originated in Southeast Asia and has spread elsewhere including Canada, Europe and the United States.

Kapil said it is likely that China's high population density, eating of exotic foods and close contact with animals on a regular basis has contributed to the spread of the disease.

"Now that the virus has been identified, scientists can begin to predict its behavior," Kapil said. "Predictions can be made about how the disease affects the body, how it spreads and what vaccines may be effective in treating it."