Queen Elizabeth II will pay tribute in her annual Christmas Day broadcast on Thursday to the "selflessness" of medical staff and aid workers fighting the Ebola epidemic.

She will say how "deeply touched" she was by the volunteers who have gone to work in areas affected by the deadly virus, according to extracts released ahead of the broadcast.

Sierra Leone's government has declared a five-day lockdown in the country's north to step up efforts to contain the Ebola epidemic, while making an exception for Christmas.

"Muslims and Christians are not allowed to hold services in mosques and churches throughout the lockdown except for Christians on Christmas Day (Thursday)," Alie Kamara, resident minister for the Northern Region, told Agence France Presse.

British scientists said Wednesday they had discovered 12 genes linked to developmental disorders in children that can cause heart defects, seizures and intellectual disability.

The genes were found in a trawl of the genomes of 1,133 children with severe, undiagnosed disorders and their parents, said the authors of a study published in the journal Nature.

A lab worker may have been exposed to a live sample of the deadly Ebola virus, the U.S. Centers for Disease Control and Prevention said Wednesday, adding the accident is under investigation.

The technician is not currently showing any symptoms of the hemorrhagic fever, which has killed more than 7,500 people in an outbreak in West Africa. 

A lawyer representing a 17-week-old fetus living inside the clinically dead body of its mother says the unborn child's right to life trumps the woman's right to a dignified death.

Conor Dignam made his closing arguments Wednesday to three Dublin High Court judges who must decide whether Ireland's anti-abortion laws permit the woman's life support machines to be turned off. Their judgment is expected Friday.

U.S. Federal officials have moved closer to overturning a decades-old ban on blood donations from gay and bisexual men, but activists say the proposed alternative would continue to stigmatize men who have sex with men.

The Food and Drug Administration said Tuesday it will recommend lifting the lifetime ban early next year, replacing it with a policy barring donations from men who have had sex with another man in the previous 12 months. The change would overturn a 31-year-old policy that many medical groups and gay activists say is no longer justified, given advances in HIV testing.

A village chief has become the first person in Sierra Leone to be jailed under laws aimed at preventing the spread of the Ebola virus, court officials and lawyers said Tuesday.

Amadu Kargbo was sentenced to six months in jail by a court in the southwestern city of Moyamba for secretly burying the dead and failing to report a sick patient, court official Foday Fofanah told Agence France Presse.

India's birth rate declined dramatically in the last two decades due in part to rising female literacy, a new study shows, but experts warned against complacency in the country of 1.2 billion.

The Total Fertility Rate -- the number of children the average woman will have in her lifetime based on current trends -- fell to just 2.3 last year from 3.6 in 1991, according to official figures released on Monday.

The Food and Drug Administration is building a legal case against companies that sell pure powdered caffeine, which can be fatal even in small doses.

The FDA warned consumers to avoid pure powdered caffeine this summer after the death of an Ohio teen. Some major retailers have stopped selling it in bulk, but the substance is still widely available on the Internet and in some stores.

More than 7,500 people have now died from the Ebola virus, as the number of cases climbs towards 20,000, the World Health Organization said Monday.

The UN health agency reported that as of December 20, 19,340 people had been infected with the deadly virus in Guinea, Liberia and Sierra Leone, and that 7,518 of them had died.