South Korea reported Friday a fourth death from Middle East Respiratory Syndrome (MERS), as an infected doctor fueled fears of a fresh surge in cases and prompted Seoul's mayor to declare "war" on the virus.

Five new cases overnight took the number of infected people to 41 in what has become the largest MERS outbreak outside Saudi Arabia, with close to 2,000 people in quarantine or under observation.

The use of traditional drugs such as heroin is falling, but new, often toxic "legal highs" are appearing at a record rate of two per week, according to a new EU report released Thursday.

A total of 101 new psychoactive substances were detected in the European Union last year, up from 81 in 2013.

A bird flu vaccine doesn't work well enough to approve it for emergency use against the outbreak that's shaken the American poultry industry, the U.S. Department of Agriculture said Wednesday.

The USDA's Animal and Plant Health Inspection Service said in a statement Wednesday that the current vaccine is not well matched against the highly pathogenic H5N2 virus and doesn't provide enough protection.

A drug nicknamed the "female Viagra" because it could help increase women's sex drive, will be discussed for a third time at a meeting of an advisory committee to US regulators Thursday.

If the US Food and Drug Administration gives flibanserin the go-ahead, it would be the first drug on the market to boost female libido.

Clutching a tiny Bible, Gilda Velasquez leans over her son as he falls asleep with the help of a powerful sedative and a catchy cartoon jingle playing on a hand-held TV.

"Remember, you're a Christian, you're a Christian," she repeats amid her tears to Yin Carlos as orderlies wheel the 6-year-old into the operating room where he will get a new liver.

Hundreds of schools closed Thursday in South Korea as officials struggled to ease growing panic over an outbreak of the MERS virus that has infected 35 people, killed two and caused thousands to cancel travel plans.

More than 900 schools -- from kindergartens to colleges -- have now shut their gates in response to public fears over what has become the largest outbreak of Middle East Respiratory Syndrome (MERS) outside Saudi Arabia.

One in three American teenagers have changed their behavior after looking up health information online, according to a major study on adolescents and technology released on Tuesday.

Of 1,156 U.S. teens aged 13 to 18 years old surveyed, 84 percent said they have used the Internet to seek out health information.

Secretary-General Ban Ki-moon warned Tuesday that as long as there is one Ebola case in West Africa "all countries are at risk" and urged all nations to support the final battles to wipe out the deadly disease in Sierra Leone and Guinea.

"We are on the home stretch now and what happens now is critical," the U.N. chief told a General Assembly meeting on efforts to end the Ebola epidemic that has killed over 11,100 people mainly in Liberia, Sierra Leone and Guinea since it was first reported in March 2014.

Nearly one in three cases of depression among young British adults may be traced to having been bullied as adolescents, a study said Tuesday.

Researchers published figures in The BMJ journal to back anecdotal evidence that victimized teenagers often go on to struggle later in life.

More than 200 primary schools shut down Wednesday as South Korea struggled to contain an outbreak of the MERS virus that has infected 30, killed two and triggered widespread fear.

With the World Health Organisation predicting further infections and the government under fire for its initial response, President Park Geun-Hye convened an emergency meeting with top health officials and medical experts to map out a comprehensive quarantine strategy.