Study confirms virus originated in wild chimps

HIV/AIDS

Studies of chimpanzee feces collected from forest floors in Africa confirm long-held suspicions that HIV, the virus that causes AIDS in humans, originated in wild chimpanzees in southern Cameroon. Working with government officials and residents of Cameroon in west central Africa, an international team of researchers collected 599 fecal samples from 10 forest sites. In examining the samples, researchers found signs of chimpanzee simian immunodeficiency virus, a close relative to HIV-1, one of the strains affecting humans. Before now, the simian version had been detected only in captive chimpanzees.

BOTTOM LINE: Confirming the origin of HIV could provide important information for scientists seeking to understand the virus's history and future, said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. ``If you're looking at the evolution of a virus, it is of great interest to get as close to the point where it jumped into humans as you possibly can."

CAUTIONS: Fecal samples reveal only genetic information, said Beatrice Hahn, a virologist at the University of Alabama at Birmingham and the study's lead researcher. ``You don't actually have a growing virus that you can study in tissue culture for various properties."

WHAT'S NEXT: Hahn and her colleagues will continue their studies of chimpanzees in the wild, looking for the origins of another HIV group, called group O. Hahn also wants to know if there are additional chimpanzee-to-human transmissions of HIV and possibly other diseases that have gone unrecognized.

WHERE TO FIND IT: Science online, May 25, 2006

KELLI WHITLOCK BURTON

OBESITY

Bust-boom cycles of eating by the poor may boost weight

Past research has found that people living in poverty are at a higher risk of becoming obese. A new study suggests why. Parke Wilde of the Friedman School of Nutrition Science and Policy at Tufts University analyzed federal survey data for 10,000 men and women that indicated height, weight, and severity of ``food insecurity," a measure of consistent access to food. The heaviest women, it turned out, were those with a moderate level of food insecurity. The reason, Wilde and colleagues said, may be found in the ``boom and bust" cycle of eating too much when food is available and too little when it is not. The story was different with men, whose weight seems to be less sensitive to economic status, for reasons that are not entirely clear.

BOTTOM LINE: Unlike in other countries, where food shortages lead to underweight people, in the United States it may be leading to obesity.

CAUTION: The study suggests that food shortage may lead to obesity. More research is needed to prove this.

WHAT'S NEXT: In future research, the government should investigate changes in the food stamp program to prevent cycles of food shortage and abundance, says Wilde. Currently, food stamp benefits are received once a month and may run out by the end of the month. If the government delivered stamps twice a month, people could ``smooth" their food availability, he said.

WHERE TO FIND IT: Journal of Nutrition, May 2006.

SENA DESAI GOPAL

COLONOSCOPY

Once every 10 years is enough for screening test

Getting a clean bill of health after a colonoscopy is good news that lasts, according to new research. Many doctors recommend patients get colonoscopies every 10 years after age 50 to catch the early signs of colorectal cancer, the second-biggest cancer killer in North America. New research confirms that time interval. It finds that patients who have a normal colonoscopy still have less risk of developing cancer a decade later. Another study in the same issue of the Journal of the American Medical Association found that colonoscopies are not warranted for patients over 80 because older people face more risk from the procedure and fewer benefits.

BOTTOM LINE: Patients who had a clean bill of health from a colonoscopy were 72 percent less likely than the general population to develop colorectal cancer after 10 years.

CAUTIONS: The results are based on averages, so there's no guarantee that an individual patient won't develop colorectal cancer within 10 years of getting a colonoscopy.

WHAT'S NEXT: Doctors are working on ways of improving screening to catch more cases early, when they are easier to treat.

WHERE TO FIND IT: JAMA, May 24/31.

GARETH COOK