Researchers at the Institut Pasteur in France, which first identified the outbreak last March, are investigating whether it could have become more contagious.

More than 22,000 people have been infected with Ebola and 8,795 have died in Guinea, Sierra Leone and Liberia.

Scientists are starting to analyse hundreds of blood samples from Ebola patients in Guinea.

They are tracking how the virus is changing and trying to establish whether it's able to jump more easily from person to person

"We know the virus is changing quite a lot," said human geneticist Dr Anavaj Sakuntabhai.

"That's important for diagnosing (new cases) and for treatment. We need to know how the virus (is changing) to keep up with our enemy."

It's not unusual for viruses to change over a period time. Ebola is an RNA virus - like HIV and influenza - which have a high rate of mutation. That makes the virus more able to adapt and raises the potential for it to become more contagious.

"We've now seen several cases that don't have any symptoms at all, asymptomatic cases," said Anavaj Sakuntabhai.

"These people may be the people who can spread the virus better, but we still don't know that yet. A virus can change itself to less deadly, but more contagious and that's something we are afraid of."

There were fewer than 100 new cases in a week for the first time since June 2014.

In the week to 25 January there were 30 cases in Guinea, four in Liberia and 65 in Sierra Leone.

The World Health Organization says the epidemic has entered a "second phase" with the focus shifting to ending the epidemic.

 

(BBC)