Though Ebola cases declined a bit last week in Guinea and Sierra Leone, responders still face a tough battle getting cases to zero with the virus expanding its range in some areas, infections spawning high-risk contacts, and illnesses reported in healthcare workers for the first time in weeks, the World Health Organization (WHO) said today.
With Liberia still free of the disease, the two remaining countries with active Ebola transmission reported 20 lab-confirmed cases last week, down from 24 the week before, the WHO said, adding that the weekly incidence has been stuck between 20 and 27 since the end of May.
Newly reported infections boost the overall number of confirmed, probable, and suspected cases to 27,443, including 11,207 deaths.
Unknown transmission still a problem
Guinea's 12 new cases were from the same four districts as the previous 2 weeks, which include Boke, Conakry, Dubreka, and Forecariah. However, the WHO said though the country's number of affected districts remained the same, the active transmission pattern has changed and in some cases expanded.
Last week Guinea reported 10 new cases.
Five of the new cases this week were in Boke district, where the transmission pattern has switched from the coastal Kamsar subdistrict to the more urbanized Boke Centre subdistrict, with no clear link between the two areas. Boke district is on the border with Guinea-Bissau.
Five infections were reported in Forecariah, which is still Guinea's most widely affected district. Three were from previously undetected transmission chains, and the WHO said it's likely that more cases will be detected in the same chain.
Dubreka and Conakry each reported a new case, and the WHO said the case in Conakry is concerning, because it came from an unknown transmission source and, like other recent cases reported in the capital, resulted in a large number of high-risk, untraced contacts.
Overall, six of Guinea's cases arose from unknown transmission chains, three of which were detected only after the individual died in the community, a sign that a number of illnesses aren't being reported and that some Ebola patients aren't being isolated and treated, a key to stopping the spread of the virus.
Sierra Leone's eight new cases came from three districts that have been hot spots over the past several weeks: Kambia, Port Loko, and Western Area Urban.
Four of the cases were in Port Loko, include two from Marampa chiefdom, that area's first since early March. Those cases involved a woman whose Ebola infection wasn't detected until she died during childbirth and the baby. The WHO said there is a substantial risk of further transmission related to the two cases, given risks posed by childbirth.
Two of the country's cases were reported in Freetown's Magazine Wharf area, the first from Western Area Urban district in 2 weeks. One is linked to a previous case, but both are associated with many high-risk contacts, the WHO said. Last week Sierra Leone reported 14 Ebola cases.
Infected healthcare workers
Three healthcare workers infections were reported, two in Guinea and one in Sierra Leone, the first since the middle of May. The WHO said that until last week Guinea had gone 2 months without a health worker infection, and Sierra Leone's last such case was reported on May 14.
Guinea's two infected health workers were from Boke district, one from Kamsar subdistrict and one from Boke Centre.
Meanwhile, the health worker who got sick in Sierra Leone is from Port Loko district's Kaffu Bullom chiefdom, an area that reported most of the country's cases over the past 3 weeks, according to the WHO. It added that the health worker is a registered contact of an earlier case and was in quarantine when symptoms began.
The trio of cases in healthcare workers pushes that total in the outbreak to 872 infections, of which 507 were fatal.
Three virus variants in Guinea
In other news, three distinct Ebola virus variants have been cocirculating in Guinea, especially in Conakry and neighboring towns, according to a gene sequencing study published in Nature today by researchers based at the Pasteur Institute in Dakar and Paris.
Their goal was to characterize how the Ebola virus evolved in Guinea between July and November 2014. They were able to sequence the virus from samples containing only small amounts of biological material based on collaboration with scientists from Harvard University's Broad Institute who were working in Sierra Leone.
They found that variant cocirculation in Guinea showed a different pattern than seen in Sierra Leone or Liberia. The investigators reported that the first variant closely resembled those seen early in the epidemic, which started in Guinea, and is detected only in Guinea, in both urban areas such as Conakry and in forested regions.
The second variant is related to the virus circulating in Sierra Leone, but could have evolved similarly in Guinea, the group reported. The sequences confirm two separate Ebola introductions into Mali in October and November 2014.
The third variant they identified came from Conakry and surrounding locations, and similarities to viruses from Sierra Leone and epidemiologic data hint at multiple Ebola reintroductions from Sierra Leone into the area around Conakry.
Though the study shows genetic diversity in the viruses that circulated in Guinea, investigators found that the mutation rate was well within those reported earlier for the Ebola virus.
Jun 24 WHO Ebola situation update
Jun 24 Nature abstract