U.S. President Barack Obama and the Red Cross have offered hope that the battle against the deadly West African Ebola outbreak is being won, amid a dramatic drop in bodies collected in Liberia's capital.

Obama on Tuesday hailed progress in the fight against the disease, which has already killed almost 5,000 people, but said Washington would remain "vigilant," and stressed that science, not fear, should guide the response to the virus.

The Red Cross said Tuesday the weekly total of Ebola victims collected by its body disposal teams around the Liberian capital is falling dramatically, indicating a sharp drop in the spread of the epidemic.

The announcement appears at odds with an assessment by the World Health Organization (WHO), which said last week transmission "remains intense" in the capitals of Liberia and neighbouring Guinea and Sierra Leone.

Is a violent criminal born that way, or shaped by childhood experiences and circumstances?

Delving into one of oldest questions in psychology, some scientists have suggested genes may contribute to roughly half of the influence -- by affecting complex brain chemistry, for instance.

Niger has seen more than 1,300 cases of cholera since the beginning of the year, with 51 people dying of the disease, the United Nations said Monday.

In September alone there were 38 reported deaths from cholera, said the U.N.'s Office for the Coordination of Humanitarian Affairs (OCHA) in the capital Niamey on its website.

Straining to hear the radio held to his ear, Wesley Wudea gestures for his grandchildren to be silent as he picks up rare tips on Ebola prevention in his own language.

In Liberia, at the center of the west African outbreak, the airwaves are often the best way to disseminate information on the epidemic, yet swathes of the ethnically diverse country do not speak the lingua franca.

Australia said Monday it was suspending migration from Ebola-hit West African nations to try to prevent the virus from crossing its borders, as a teenager who arrived from Guinea tested negative for the disease.

Immigration Minister Scott Morrison told parliament the government had stopped issuing visas to people from those countries hit by the disease, which has claimed close to 5,000 lives in its worst outbreak.

Fujifilm said Monday it would buy a U.S. vaccine maker as the Japanese firm boosts its supply of an experimental Ebola drug to help stem the spread of the virus.

The deal would see Fujifilm take a 49 percent stake in Kalon Biotherapeutics, with plans to buy the whole company "in the future", the company said, without supplying financial details.

Bioactive ingredients found in cocoa sharply reversed age-related memory decline in a group of volunteers, scientists reported on Sunday.

The compounds, called flavanols, were taken in a specially-prepared cocoa drink, according to an experiment published by the journal Nature Neuroscience.

Scientists in Denmark said Sunday they had found genetic clues to explain why a small number of children have febrile seizures -- brief convulsions -- after receiving the measles, mumps and rubella (MMR) vaccine.

They stressed there was no need to scrap the MMR vaccine -- caught in a health scare in 1998 that watchdogs later declared groundless -- and described its use as a "great achievement" in saving lives.

The seven-inch scar runs diagonally across the left flank of his skinny torso, a glaring reminder of an operation he hoped would save his family from debt but instead plunged him into shame.    

Chhay, 18, sold his kidney for $3,000 in an illicit deal that saw him whisked from a rickety one-room house on the outskirts of the Cambodian capital Phnom Penh to a gleaming hospital in the medical tourism hub of neighboring Thailand.