People with an algae virus in their throats had more difficulty completing a mental exercise than healthy people, and more research is needed to understand why, US scientists say.

A study in the Proceedings of the National Academy of Sciences showed that the virus was present in about half of 92 human subjects studied, and those who had it performed worse on certain basic tasks.

A second person from Mali has died from Ebola, just as hardest-hit Liberia hailed a dramatic drop in infections and the last-known sufferer in the United States was declared cured on Tuesday.

The death of a nurse who had treated an Ebola patient from neighboring Guinea came as a blow to authorities in Mali, just as they were beginning to lift quarantine restrictions on more than 100 people exposed to the country's first victim of the virus.

A group of more than 300 prominent doctors, religious leaders and ethicists on Wednesday urged President Barack Obama to change the current system for organ donation, saying too few people get life-saving transplants.

In an open letter to the Obama administration, the group called for the government to start researching ways to make organ donation more appealing to the general public, in order to end a chronic shortage of organs that is getting worse each year.

Health Minister Wael Abu Faour raised the alarm on Tuesday over food safety in the country, warning that “the food that the Lebanese are eating is full of diseases.”

“A large number of foodstuffs firms are operating without licenses and without meeting the proper health conditions,” the minister announced at a press conference.

Scientists said Monday they had found a variant of a gene that confers a near five-fold protection against typhoid fever, which affects millions of people each year.

The discovery, that came from screening the genomes of hundreds of infected people and healthy controls in Vietnam and Nepal, may aid the development of better vaccines for typhoid and other bacterial diseases, said the authors of a study published in Nature Genetics.

Canada on Monday ramped up travel restrictions for people returning from Ebola-stricken countries, officials said, and said "high risk" travelers should be closely monitored for symptoms or admitted to a special facility.

People returning from Liberia, Guinea or Sierra Leone who have come into contact with the virus are told to report to local health officials and self-monitor for up to 21 days, Canada's Public Health Agency said.

Eight women have died in India and dozens more are in a critical condition after a state-run sterilization program designed to control the country's billion-plus population went badly wrong.

More than 60 women are in hospital after suffering complications from the surgery over the weekend and 24 of them are seriously ill, authorities in the central state of Chhattisgarh said Tuesday.

A Maine nurse who battled politicians over her quarantine after she returned from treating Ebola patients in West Africa said she will continue speaking out on behalf of public health workers.

Monday marks the 21st day since Kaci Hickox's last exposure to an Ebola patient, a 10-year-old girl who suffered seizures before dying alone without family.

Uzbekistan has temporarily suspended travel to and from Ebola-hit African countries, and issued an alert about visits to Western and East European nations.

The Central Asian state's anti-Ebola commission has banned anyone travelling from Guinea, Sierra Leone, Liberia, the Democratic Republic of Congo, Nigeria, Senegal and Mali from entering the country.

The last region of Sierra Leone to be affected by Ebola, Koinadugu, in the north-east of the country, has seen 50 people die from the virus in recent weeks, according to the Red Cross.

"Fifty people have died since mid-October," the head of the Red Cross in Sierra Leone, John Marah, told Agence France Presse.