Geneva, Sep 23 (IANS/EFE): Cases of the deadly Ebola virus disease (EVD) could exceed 20,000 within five to six weeks if measures to control the epidemic are not immediately strengthened, leading experts said in an article published Tuesday.

Liberia, Guinea Conakry and Sierra Leone were, in order of severity, the countries where the Ebola virus is most intensely circulating, according to the article in The New England Journal of Medicine.

According to experts from the World Health Organisation (WHO) and Imperial College London, nearly half of the 20,000 cases will be in Liberia, followed by 5,700 in Guinea Conakry and 5,000 in Sierra Leone if the disease's current trends continue.

Imperial College London epidemiological statistics professor and co-author, Christl Donnelly, said the estimates were obtained using two different methodologies and they match the predictions of other medical organisations.

The difference, however, is that until a few weeks ago, it was believed that 20,000 cases would not be reached until next February or March, not just over a month from now.

The most recent data provided by WHO indicates that there have been 5,800 cases registered so far with 2,800 deaths.

In formulating the projections, scientists have taken into account that a week ago the number of infected individuals in Guinea Conakry had doubled in just 15.7 days, in 23.6 days in Liberia, and in 30.2 days in Sierra Leone.

The study highlights that this Ebola epidemic has not seen any changes in clinical characteristics, the severity of the infection or in transmission mode compared to previous outbreaks.

"The incubation period, duration of illness, case fatality rate and reproduction number (people infected by each patient)) are all within the ranges reported for previous EVD epidemics," the article said.

The exceptionally large nature of this epidemic is due to the characteristics of the infected population and the efforts made to halt transmission, which have been insufficient, according to the researchers.

The extremely poor healthcare systems of the three countries after years of armed conflict, have also been a factor.

Nigeria, however, which boasts a better healthcare system, quickly had the epidemic under control with a limited number of cases and has apparently managed to stop transmission.

This came despite the fact that the virus was introduced in Lagos, a city of 20 million people, and Port Harcourt, another large metropolis.