A new study shows that people living in areas where uptake of HIV treatment is high are less likely to acquire the virus than in places where few are given care, UNAIDS said Thursday.

The research by the Africa Centre for Health and Population Studies marks the first time that the positive impact of antiretroviral therapy on infection rates has been proven for a community, said the U.N. agency.

About 13 million people living in west and central Africa face a major food crisis unless immediate action is taken, humanitarian group Oxfam warned Thursday.

A dangerous combination of drought, high food prices, reduced harvests, poverty and conflict are driving an emerging crisis across several nations including Chad, Burkina Faso, Mali, Mauritania, Niger and northern Senegal, the group said.

About 1,000 women die each day in childbirth or from preventable complications related to pregnancy, humanitarian group Medecins Sans Frontieres (Doctors Without Borders) said Thursday.

"Worldwide, at any time, 15 percent of pregnancies incur the risk of a potential fatal complication," said Kara Blackburn, responsible for women's health at MSF in a statement to mark International Women's Day.

Married adults are more than three times more likely to survive the critical first three months after heart surgery than their single counterparts, according to a U.S. study released Wednesday.

"That's a dramatic difference in survival rates for single people, during the most critical post-operative recovery period," said sociologist Ellen Idler, lead author of the study in the Journal of Health and Social Behavior.

The most widely prescribed drug to treat mild Alzheimer's disease, Aricept (donepezil), has been shown for the first time to help patients with more severe cases too, a study said Wednesday.

The research was funded by the UK Medical Research Council and the Alzheimer's Society, and received donated pills from the pharmaceutical companies Pfizer-Eisa and Lundbeck but drug makers were not otherwise involved.

Scientists are reporting what could be very bad news for efforts to customize cancer treatment based on each person's genes.

They have discovered big differences from place to place in the same tumor as to which genes are active or mutated. They also found differences in the genetics of the main tumor and places where the cancer has spread.

More work needs to be done to keep young Americans from using tobacco, including creating smoking bans and increasing taxes on tobacco products to deter youth, the U.S. Surgeon General's office said in a report released Thursday.

The report said it's particularly important to stop young people from using tobacco because those who start smoking as teenagers can increase their chances of long-term addiction. They also quickly can develop reduced lung function, early heart disease and other health problems.

U.S. health authorities on Tuesday issued a warning to the maker of a new inhalable caffeine product sold in the United States and France, citing mislabeling and safety concerns.

"The Food and Drug Administration reviewed your website at www.aeroshots.com in February 2012 and has determined that the product AeroShot is misbranded," said the letter. "We also have safety questions about the product."

The United Nations Children's Fund on Tuesday appealed to western African governments to prevent a new cholera outbreak, after the disease claimed nearly 3,000 lives there last year.

Unicef's regional bureau said that "at least 105,248 cases of cholera were registered in 17 countries in 2011, and 2,898 people died" in what was one of the most severe outbreaks of the disease in years.

British scientists have discovered a type of antibody in mice that blocks a hallmark of Alzheimer's disease, offering a potential new route to treatment, according to research published on Tuesday.

The antibodies shut down a protein called Dkk1 that in turn stops the formation of amyloid plaque in the brain, a key factor in the progression of Alzheimer's, said the findings in the Journal of Neuroscience.