Washington, Jan 30 (IANS): The number of new cases of Ebola Virus Disease (EVD) in the three worst-affected countries of Guinea, Sierra Leone and Liberia has fallen to the lowest level since late June, the World Health Organisation (WHO) said Thursday.

The three countries had a combined total of 99 new cases for the week ending Jan 25, CNN reported , citing the WHO.

Out of this total of 99 new cases, 65 were reported from Sierra Leone, 30 from Guinea and four from Liberia.

The number of cases continued to fall in Liberia and Sierra Leone, WHO said, but Guinea's figure rose from 20 confirmed cases in the previous week.

The western Guinean district of Forecariah, where the local community has shown high resistance to measures for limiting the spread of the disease, was the worst hit, reporting half of the new cases for the week.

WHO said that the response to the Ebola epidemic has now moved to a second phase, "as the focus shifted from slowing down transmission to ending the epidemic".

"To achieve this goal as quickly as possible, efforts have moved from rapidly building infrastructure to ensuring that capacity for case finding, case management, safe burials, and community engagement is used as effectively as possible."

There have been more than 22,000 reported confirmed, probable and suspected cases since the Ebola outbreak began, with almost 8,800 known deaths.

According to the latest WHO report, children are less susceptible than adults to contracting the virus, which spreads through direct contact with an infected person's bodily fluids.

People aged 15 to 44 years are approximately three times more likely to be affected than children aged up to 14 years, while adults aged 45 years and above are almost four times more likely than children to be affected.

Even as the number of cases drops, scientists around the world continue to study the virus to understand how it works and help develop more effective vaccines against it.

Anavaj Sakuntabhai, human geneticist at the Pasteur Institute in Paris, is part of a team working to sequence the virus and monitor how it mutates.

"It's very important for us to follow what happens with the virus sequence," he told CNN.

While the virus is not that mutated yet, he said: "It's important for us to monitor how it changes and see whether it is more contagious or more lethal."

His team is using blood samples collected from Guinea and processed by colleagues based in Dakar in Senegal.

Sakuntabhai's team has sequenced about 20 samples so far and hopes to do another 100 in the coming weeks, ultimately sequencing several hundred.

People have been anxious to know if the virus could mutate to become airborne, but it does not appear to be easy for it to mutate sufficiently to alter the mode of transmission, according to Sakuntabhai.

He said that it was normal for the virus to change and that it was "not something to be frightened of at the moment".

The Ebola virus disease, previously known as the Ebola hemorrhagic fever, is a severe illness in humans, often fatal, according to the WHO. The virus is passed on to people from wild animals and can be transmitted from humans to humans. The average Ebola death rate is about 50 percent.

The first outbreaks of EVD occurred in remote Central African villages, near tropical rainforests. However, major urban and rural areas have been involved in the outbreak in western Africa.

No licensed treatment has yet been proven to be able to neutralise the virus, but a number of blood, immunological and drug medications are under development.