The World Health Organization have announced that the Ebola virus in the new outbreak in the Democratic Republic of Congo is not derived from strains circulating in the current outbreak in West Africa.

“Results from virus characterization, together with findings from the epidemiological investigation, are definitive: the outbreak in DRC is a distinct and independent event, with no relationship to the outbreak in West Africa,” says a situation statement the World Health Organization (WHO) released on Tuesday.

Virus sequencing of samples shows the Democratic Republic of Congo (DRC) strain is the Zaire strain, which is indigenous to the DRC and closely related to the strain that caused DRC’s 1995 Ebola outbreak.

Ebola first emerged in humans in 1976 in simultaneous outbreaks in Nzara in Sudan (now South Sudan) and Yambuku in Zaire (now DRC). The DRC outbreak occurred near the Ebola river, from which the virus takes its name.

The new DRC outbreak, the seventh since 1976, is centered around the remote district of Boende in the province of Equateur in the northwest of the country.

The lab report from a WHO collaborating centre in Franceville, Gabon, clearly states that “the virus in the Boende district is definitely not derived from the virus strain currently circulating in West Africa.”

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WHO state that “the virus in the Boende district is definitely not derived from the virus strain currently circulating in West Africa.”

WHO describe the finding “reassuring” because it excludes the possibility that the virus has spread from West to Central Africa.

The authorities are linking the index case in the new DRC outbreak to bushmeat consumption.

The index case was a pregnant woman who fell ill after butchering a bush animal. This is consistent with the pattern set at the start of previous outbreaks in DRC, where the virus moves from animals (usually fruit bats or monkeys) to humans via contact with their meat.

So far, 53 cases consistent with the definition for Ebola virus disease, including 31 deaths, have been identified. More than 160 contacts are being traced.

The authorities say human-to-human transmission has been established in the new DRC outbreak. The deceased include relatives and health workers who cared for the pregnant woman, and other clinic staff who came into contact with them. Other individuals who handled the bodies of the dead to prepare them for funerals have also died.

Unlike the outbreak in West Africa, the new one in DRC has not affected well-populated areas. The area with the most intense transmission is remote, located about 1,200 km from the capital Kinshasa, and there are no paved roads connecting it to the city.

“However,” the WHO statement cautions, “cases have been detected or transmission is ongoing at three sites, underscoring the need to watch the outbreak’s evolution closely.”

DRC already has an established infrastructure of emergency committees at national, provincial and local levels, and is activating these and setting up isolation centers and ensuring community leaders are made aware of the facts about the disease. The DRC government says it will also ensure that burials are safe.

WHO describe the level of collaboration between DRC authorities and its key partners as “excellent.” The UN agency says canoes, motorcycles and satellite phones – and soon a helicopter – are being supplied to help with investigations and tracing the contacts.

WHO do not recommend travel restrictions to and from DRC for people who have not been in contact with cases of Ebola.

Meanwhile, a recently published gene study of 99 virus genomes has traced the origin of the current Ebola outbreak in West Africa. It found over 300 mutations that distinguish the current strains from those of previous outbreaks, and the outbreak likely started from a single introduction into humans that then spread over many months.