Immunologists expressed concern Friday about the "dangerous" work of scientists in China who created a hybrid bird flu virus that can spread in the air between guinea pigs, and now lives in a lab freezer.

The team from the Chinese Academy of Agricultural Sciences and Gansu Agricultural University wrote in the journal Science they had created a new virus by mixing genes from H5N1 "bird flu" and H1N1 "swine flu".

Five Saudis who died after contracting a new SARS-like virus last week had not travelled abroad, a health ministry doctor said on Saturday.

"After questioning relatives, it turned out that none of these people had been abroad before being infected," Dr Ziad Mimish, who heads the ministry's disease prevention unit, told Agence France Presse.

The U.S. food and drug regulator on Friday called the addition of caffeine to children's foods like chewing gum and jelly beans "dangerous" and warned of a possible crackdown.

Food and Drug Administration deputy commissioner Michael Taylor said the rise in such caffeine-added products outside the beverage industry was "very disturbing," after candy giant Mars Inc. announced a caffeinated version of its Wrigley gum.

Some of the most devastating forms of cancer have genetic similarities even though they strike different body parts, according to new studies out Thursday.

The new research -- one study focused on a form of leukemia, in the New England Journal of Medicine, and a second on endometrial cancer, in Nature -- could offer a pathway to new, more effective treatments.

Suicide rates are rising dramatically among middle-aged Americans, according to U.S. government statistics, which showed a 28 percent spike from a decade ago in the number of people taking their own lives.

The U.S. Centers for Disease Control and Prevention said the figures show more people taking their own lives than dying in car accidents, and attribute the increase to the sharp rise in suicides among adults aged aged 35 to 64.

China has detained 900 people for meat-related crimes including selling rat and fox meat as beef and mutton, the public security ministry said, in another blow to the nation's food safety.

News of the three-month operation added to a string of scandals that have galvanized public concern from recycled cooking oil to dangerous chemicals in baby milk powder.

Chinese police have arrested the head of a kindergarten and her associate over the deaths of two children from a rival school who ate yogurt injected with rat poison, state media said Friday.

The five- and six-year-old girls from northern Hebei province died after eating the yogurt which they had found in a bag on the side of the road while walking to school with their grandmother.

Playing videogames can prevent and even reverse deteriorating brain functions such as memory, reasoning and visual processing, according to a study released Wednesday.

The University of Iowa study of hundreds of people age 50 and older found that those who played a videogame were able to improve a range of cognitive skills, and reverse up to seven years of age-related declines.

An international team of surgeons has successfully given a South Korean-Canadian toddler a life-saving windpipe transplant made from plastic fibers and some of her own stem cells.

Hannah Warren, 2, was born without a trachea and is now the youngest person to ever receive a bio-engineered organ, after an operation in the United States.

A U.S. doctor has created a website to make it easier for the world's sickest people to connect with research that could potentially save their lives.

The non-profit endeavor known as MyClinicalTrialLocator.com aims to become "the Wikipedia of clinical trials," by allowing a quick and free search for studies at academic centers around the globe, said its founder Bruce Moskowitz.