Chronic fatigue syndrome is a disease with distinct stages that can be identified through biomarkers in the blood, researchers said Friday, offering hope that earlier diagnosis may improve treatment.

Scientists at Columbia University's Mailman School of Public Health said their findings represent "the first robust physical evidence" that the syndrome is "a biological illness as opposed to a psychological disorder, and the first evidence that the disease has distinct stages."

People who use personal audio players should consider limiting their use to one hour a day and turn down the volume to prevent permanent hearing loss, the World Health Organization said Friday.

The U.N. agency said young people are particularly at risk. with data from middle- and high-income countries showing that almost half of all 12- to 35-year-olds listen to their personal audio devices or cellphones at unsafe volumes. About 40 percent of young people are also exposed to damaging sound levels at nightclubs, bars and sporting events.

Liberian President Ellen Johnson Sirleaf on Friday praised President Barack Obama's "extraordinary" leadership in the fight against the Ebola outbreak in West Africa.

With Liberia now in recovery from the worst outbreak ever of the deadly virus, the United States ended its military mission in the region Thursday.

Ten more people in Saudi Arabia have died from MERS over the past week, health ministry figures showed on Friday, after an international mission urged extra measures to combat the virus.

Saudi Arabia is the country worst-hit by Middle East Respiratory Syndrome coronavirus (MERS-CoV).

People who drink four to six cups of coffee daily may be less likely to get multiple sclerosis, according to international research out Thursday.

"Caffeine intake has been associated with a reduced risk of Parkinson's and Alzheimer's diseases," said lead author Ellen Mowry of the Johns Hopkins University School of Medicine in Baltimore, Maryland.

Over a million people have received blood and marrow stem cell transplants for life-threatening diseases in the past 57 years, but too many are still waiting, a study said Friday.

Haematopoietic stem cell transplantation (HSCT) often offers the only possibility of a cure for blood diseases and rare cancers like myeloma or leukaemia.

Japanese health authorities said Friday that they have ordered the local unit of Swiss pharmaceutical giant Novartis to temporarily suspend its operations for failing to report drug side effects.

The health ministry's 15-day suspension -- reportedly a first for a pharmaceutical firm operating in Japan -- means the company will not be able to sell most of its drugs during that period, which is to start from March 5.

A small molecule derived from an Asian herb may help stop Ebola infection by preventing the virus from entering the cells of the body, researchers said Thursday.

So far the research using the calcium channel blocker Tetrandrine, found in some Chinese and Japanese herbs, against Ebola has only been done in lab animals and in petri dishes.

Australia is set to strengthen food labeling laws after a series of hepatitis A infections were linked to frozen berries from China, Prime Minister Tony Abbott said Thursday.

Nanna's and Creative Gourmet brand raspberries and mixed berries were recalled after being linked to some 19 hepatitis A cases across the country this month, with poor hygiene or contaminated water at their packing factory thought to be responsible.

A nasty intestinal bug sickens nearly twice as many Americans each year as was previously thought, according to the largest U.S. study to look at the problem.

The germ — Clostridium difficile, or C-diff — flourishes in the gut after antibiotics kill off other bacteria and causes diarrhea. It can be severe and is blamed for about 15,000 deaths annually — mainly in the elderly.