The number of people believed to have been killed by the Ebola virus in Guinea has passed 100, the World Health Organisation (WHO) says.
Another 10 have died in neighbouring Liberia, the BBC reports.
The disease is spread by close contact and kills up to 90 percent of its victims.
WHO assistant director-general Keija Fukuda said the organisation was the most challenging Ebola outbreak it had dealt with.
It was important people understood how the disease spread to prevent a panic, Mr Fukuda said.
"It's absolutely critical to get out as much accurate information as possible to the communities, to the countries that are affected, really to address the anxiety and reduce the rumours as much as possible so people have facts to work with, not just rumours."
This is the first known Ebola outbreak in Guinea; most recent cases have been thousands of miles away in the Democratic Republic of Congo and Uganda.
The tropical virus leads to haemorrhagic fever, causing muscle pain, weakness, vomiting, diarrhoea and, in severe cases, organ failure and unstoppable bleeding. There is no known cure for it.