Several American healthcare workers who may have come in contact with a US volunteer who tested positive for Ebola in Sierra Leone are being monitored for signs of illness, officials said Friday.

The patient, whose identity has not been revealed, was in serious condition after arriving by private charter plane at the National Institutes of Health Clinical Center near the US capital early Friday.

South African doctors announced Friday that they had performed the world's first successful penis transplant, three months after the ground-breaking operation.

The 21-year-old patient had his penis amputated three years ago after a botched circumcision at a traditional initiation ceremony.

Ten more people have died in Saudi Arabia from the MERS virus since last week, health ministry data showed on Friday, adding to a surge in cases over the past month.

The latest deaths occurred between March 6 and 12, mostly in the capital Riyadh, bringing to 17 the number of MERS deaths so far this month, according to the ministry.

The global death toll from the Ebola outbreak centered in west Africa has topped 10,000 out of more than 24,000 recorded cases, the World Health Organization said Thursday.

Almost all the deaths and cases have been reported in the three west African countries worst hit by the outbreak: Sierra Leone, Liberia and Guinea.

A German biologist who promised to pay 100,000 euros to anyone who could prove that the measles was indeed a virus was ordered by a court on Thursday to hand over the money.

The man had made the promise in 2011 on his website, saying anyone who could offer scientific proof of the existence of the virus would receive the $106,000 reward.

Smoker numbers are declining in many parts of the world, but upward trends in African and Mediterranean countries mean the global total will not change much over the next 10 years, researchers said Friday.

The U.N.'s World Health Organization (WHO) estimates that about six million people die around the world every year from smoking-related causes -- more than five million from direct tobacco use and the rest from second-hand smoke.

Every evening for months the sky would turn orange as Liberia's Ebola crematorium roared into life, its towering flames reducing victim after victim to ash and blackened bone.

It was a ritual that the villagers of Boys Town came to dread, the thick black smoke and smell of death permeating their homes and spreading alarm in the community.

The world can beat the liver-attacking hepatitis B virus, which results in some 650.000 deaths a year, the World Health Organization said Thursday, releasing its first treatment guidelines for the disease.

"Viral hepatitis is certainly an epidemic, a pandemic, but it is one that remains silent," said Gottfried Hirnschall, head of WHO's HIV/AIDS department.

Can a tetanus shot help treat brain cancer? A small study hints that it might.

A dose of tetanus vaccine let patients live longer when added to an experimental treatment for the most common and deadly kind of brain tumor, researchers report.

A female British healthcare worker who contracted Ebola in Sierra Leone was being flown home for treatment on Thursday, the Ministry of Defense said.

A Royal Air Force plane sent to the west African country on Wednesday is bringing the military servicewoman back to be treated in London's Royal Free Hospital, an MoD spokeswoman said.