An American healthcare worker who has been in Sierra Leone will be placed under close observation at a Nebraska hospital after high-risk exposure to the Ebola virus, doctors said on Saturday.

The unnamed patient will arrive on Sunday aboard a private air ambulance for observation and possible treatment.

The government of war-torn Somalia has moved to reassure residents that there was no outbreak of Ebola in the country, dismissing rumors that a man had brought the virus back with him from Guinea.

"As soon as we heard the rumors of a case of Ebola virus in Somalia, we acted quickly and decisively to isolate the alleged victim, a Somali citizen named Abdulkadir Jinow Barow, and those who had been in contact with him," Health Minister Ali Mohamed Mohamud told reporters.

A British nurse who contracted Ebola in Sierra Leone and was hospitalized in London this week is now in a "critical" condition, the hospital treating her said Saturday.

"The condition of Pauline Cafferkey has gradually deteriorated over the past two days and is now critical," the Royal Free Hospital in London said in a statement.

A member of a South Korean medical team treating Ebola patients in Sierra Leone has been flown to Germany after suffering an injury with a hypodermic needle.

Berlin's renowned Charite hospital said in a statement that the unidentified medic was taken to its special isolation unit Saturday.

West Africa still has a long way to go to beat Ebola, the United Nations' outgoing Ebola mission chief said Friday.

"I think the response has been successful but we have a long way to go," Anthony Banbury, head of the U.N. Mission for Ebola Emergency Response (UNMEER) said, warning of an "epic battle" still ahead to control the spread of the virus.

U.S. scientists encouraged 20 obese people to eat extra fast food for several months, and found that about a quarter stayed in good health despite the additional pounds they gained.

The study in the January 2 edition of the Journal of Clinical Investigation was led by a team of scientists at Washington University School of Medicine in St Louis, Missouri.

Randy Gross hopes a new law allowing children into Illinois' medical marijuana program will reunite his family, nearly a year after his wife moved to Colorado so their son could receive a controversial treatment to ease his epileptic seizures.

Gross lives and works in Illinois. His wife, Nicole, moved with their two sons so their 8-year-old could legally swallow a quarter-teaspoon of marijuana oil each day. While the medical evidence is thin, some parents — including the Grosses — say marijuana works for their children and they're willing to experiment.

The tequila sure looks real, so do the beer taps. Inside the hospital at the National Institutes of Health, researchers are testing a possible new treatment to help heavy drinkers cut back — using a replica of a fully stocked bar.

The idea: Sitting in the dimly lit bar-laboratory should cue the volunteers' brains to crave a drink, and help determine if the experimental pill counters that urge.

Cancer is often caused by the "bad luck" of random mutations that arise when cells divide, not family history or environmental causes, U.S. researchers said Thursday.

The study in the January 2 edition of the journal Science was led by researchers at Johns Hopkins University and based on a statistical model that includes many types of cancer in a range of human tissues.

An Italian doctor who contracted Ebola in west Africa has recovered from the disease after undergoing experimental treatment, local media reported on Thursday.

The 50-year-old from Sicily, who has not been named, has been in isolation at Rome's Spallanzani institute since he was evacuated from Sierra Leone in mid-November.