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Key found to spread of SARS

Chinese scientists analyzing the genome of the SARS virus have documented the startling rapidity of its evolution from an animal pathogen into one able to infect human cells.

Their analysis, being reported today in the journal Science, shows that as the virus perfected its human attack mechanism, its potency soared. Early on, it was able to infect only 3 percent of the people who came in contact with a patient; a few months later, the infectivity rate was 70 percent.

The speed of the transformation indicates the importance of identifying and isolating patients at the earlier possible stage to prevent widespread viral epidemics.

X-rays, CT scans called

small source of cancer risk

LONDON _ The risk of cancer from common X-rays and increasingly popular CT scans ranges from less than 1 percent to about 3 percent, according to a new study.

In the United States, doctors have urged caution about unnecessarily using the scans on children. They are more sensitive to radiation and exposure is cumulative.

The new research indicates the cancer risk _ ranging from 0.6 percent to 3.2 percent _ varies depending on the frequency of X-rays and scans in 15 countries surveyed. Experts not involved in the study wrote in the journal the Lancet, which published the findings, that the benefits of X-rays and CT scans far outweigh the risk.

NIH chief explains basis

of sexual behavior studies

Responding to criticism from conservatives, the director of the National Institutes of Health has told lawmakers that the government should continue to pay for studies of sexual behavior because they could have a powerful impact on public health.

Last fall, the Traditional Values Coalition accused the institutes of paying for studies of "bizarre sexual practices with little or no bearing on public health." The group asked Rep. Billy Tauzin, R-La., chairman of the House Energy and Commerce Committee, to investigate.

Among the projects were a study of truckers, prostitutes, drug use and sexually transmitted diseases, and studies of sexual behavior in older men, sexual risk-taking and sexual dysfunction.

In a letter sent late Wednesday to lawmakers, the institutes' director, Dr. Elias Zerhouni, said the battle against disease must include behavioral and social factors, not just biological ones.

Even 3-year-olds

can be couch potatoes

New research suggests even 3-year-olds aren't getting enough exercise, raising concerns over their weight, future disease risk, psychological well-being, behavior and learning ability.

In the first study to rigorously track the movements of preschoolers, scientists found that the average 3-year-old is physically active for just 20 minutes a day, well short of the recommended hour a day.

In the Lancet study published this month, scientists from the University of Glasgow in Scotland monitored 78 children. The toddlers were burning about 1,300 calories a day _ less than the 1,500 calories recommended.