People who are obese in middle age run a lower risk of developing dementia later, said a large and long-term study Friday whose findings challenge the prevailing wisdom.

On the other end of the scale, however, being underweight in the 40-55 age bracket was associated with a higher risk, the researchers found.

Drug-resistant tuberculosis is a major health challenge across much of Africa, but a new medicine being pioneered in South Africa could be a breakthrough after decades of frustration.

Bedaquiline is being made available to 3,000 people suffering side effects of the usual drug-resistant tuberculosis treatment, or who have developed complete drug resistance.

Short people face a greater lifetime risk of clogged arteries, according to a study out Wednesday that confirmed the long-known link between height and heart disease by examining genetics.

The study is the first to show that the higher risk is primarily due to a variety of genes that influence whether a person is tall or short, and not potentially confounding factors like poverty or poor nutrition.

Canadian health officials broadened a quarantine around two turkey farms to nine Wednesday, after H5 bird flu was detected in one of them.

The virus was detected on a farm near Woodstock, Ontario, about 100 kilometers southwest of Toronto, after the sudden deaths of birds over several days.

A 27-year-old U.S. woman from New York state who killed her five-year-old son by poisoning him with salt was jailed for 20 years on Wednesday.

Judge Robert Neary said while Lacey Spears suffered from the mental illness known as Munchausen by proxy, she was guilty of a crime "unfathomable in its cruelty."

A Japanese research team said Thursday it had developed a field test for Ebola that gives results in just over 11 minutes -- down from the 90-minute test used now.

The breakthrough by Nagasaki University's Institute of Tropical Medicine will allow medics to move much more quickly in treating people with the haemorrhagic fever, Professor Jiro Yasuda told Agence France Presse.

The United Nations launched a food safety campaign Tuesday for an era in which millions are dying of hunger or tainted produce even as more and more people fall ill from eating too much.

"Food safety, quality and quantity must go together," Margaret Chan, director general of the U.N. World Health Organization (WHO), said at Paris' Rungis wholesale market, where she launched World Health Day 2015 under the theme: "From farm to plate, make food safe."

Two turkey farms in Canada have been placed under quarantine after H5 bird flu was detected in one of them, Canadian health authorities said.

The Canadian agency responsible for food inspections said it was conducting further tests to determine the precise strain of the virus and the severity of the infection.

Workers in Chile began harvesting the country's first medical marijuana crop Tuesday, breaking new ground in cancer treatment in a nation where cannabis is outlawed as a hard drug.

With the blessing of local authorities, the Daya Foundation, a charitable group, began harvesting some 400 plants sown last October under a special permit to extract cannabis oil to be given free of charge to 200 cancer patients as pain treatment.

Sierra Leone said on Tuesday it had wrongly reported Ebola as the cause of a baby's death in a part of west African country which had been declared free of the virus weeks ago.

Villagers in the eastern district of Kailahun were dismayed when the government said on Monday a nine-month-old boy had tested positive after his death, more then three months after the last confirmed Ebola case.