|SARS May Still Be Jumping from Animals to People|
By Kate Ruder
Posted: January 29, 2004
The finding strengthens the argument that the SARS epidemic originated in animals, the researchers report today online in the journal Science. It is part of a larger study by the Chinese SARS Molecular Epidemiology Consortium that tracked genetic changes in the virus during three stages of the epidemic.
Apparently, the virus successfully adapted to humans and became more infectious over time, the researchers conclude. The study underscores the importance of detecting infections early on as a way to contain the disease.
“When the [SARS] virus invaded the human population, it went through phases of adaptation, and it gradually found a comfortable niche in the human population,” says Chung-I Wu of the University of Chicago in Illinois, who was a member of the research team.
As the virus evolved, it became more infectious. Early on, only one percent of people that came in contact with infected people became infected themselves; later, the rate of infection was nearly 70 percent.
In the study, the researchers compared the genomes of about 60 SARS viruses isolated during the early, middle, and late stages of the epidemic. Several SARS-like viruses from Himalayan civet cats were also part of the analysis.
The SARS virus went through three distinct phases during its evolution in humans.
The middle phase of the virus’s evolution (January 31-February 21, 2003) was characterized by more person-to-person infections. Viruses from the middle phase all had a common genetic fingerprint.
By the late phase (after February 2003), the SARS virus had fully adapted to living in humans.
The person hospitalized last month with SARS was a television producer in the city of Guangzhou. How he contracted the virus is not clear, but his case indicates that there’s still a danger of SARS-like viruses moving from animals to people.