Despite its lower profile in the news, the battle against Ebola Virus Disease has not yet been won. Liberia has been declared Ebola-free, for the second time, but there’s ground to cover in neighboring countries Guinea and Sierra Leone. After this epidemic is finally stopped, the threat of Ebola remains as outbreaks have plagued the African continent since the virus emerged in 1976.
The number of new Ebola cases have waned in West Africa, but every new case is a threat to as many as thousands of others. A new case of Ebola had been found in Kambia district in northern Sierra Leone over the weekend, said the World Health Organization in a news release. Under heightened surveillance policies, all people who have died at home are being tested for the virus. A deceased woman around 60 years of age had been swabbed for the virus on August 29 and tested positive.
“Although no-one wanted to see more cases of Ebola virus disease in Sierra Leone, we kept all our teams on alert and ready to respond and close down any new transmission” said Dr. Anders Nordstrom, WHO representative in Sierra Leone.
A rapid response team has been deployed to Kambia to identify contacts and test people who may have been exposed, said a WHO report. Strategies to quash the spread of the virus, which has caused 11,290 deaths to date, has been surveillance and containment as well as using an experimental vaccine.
The Phase 3 efficacy trial of the VSV-EBOV vaccine (Merck) has now been extended from Guinea to Sierra Leone based on interim results published by the Lancet that found the experimental vaccine to have 100% efficacy. Health workers will use a “ring vaccination” strategy is meant to develop Ebola immunity within a group of people who are most likely to get infected. Direct and indirect contacts associated with the confirmed case in Kambia will be offered the vaccine.
Despite the astonishingly good results, this particular Ebola vaccine probably won’t end Ebola for good on its own. Because it’s a single-dose vaccine, immunity will wear off. Ebola outbreaks Africa happen periodically, which means that the vaccine’s temporary immunity is not enough to stop Ebola.
Ongoing surveillance and testing of any suspected cases of or exposures to Ebola throughout West Africa is critical, even in Liberia which is in a 90 day watch period.
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“If you look at the latest statistics — 4 to 5 cases, but there may be 4,00o to 5,000 contacts,” said Dr. David Persing, chief medical and technology officer of Cepheid, the maker of the Xpert Ebola Assay. “Five cases is not a lot, but a [rapid testing team] has the ability to go in and look at the 2,000 contacts and treat people early.”
The WHO said there is an urgent need for rapid Ebola tests because conventional methods took days, even weeks to deliver a test result. People with undiagnosed Ebola were out in their communities unaware they needed urgent help. Those without Ebola, but in isolation were cut off from their families and were at risk of acquiring the virus in the health center.
Cepheid’s assay can produce results in under an hour, but getting rapid tests to be adopted has been challenging.
“Healthcare providers need confidence in the result. They don’t believe a [negative] test result,” said Dr. Persing.
The tests need to be sensitive (identify Ebola cases), but also need to be specific (avoid false positives). With the current prevalence being low, false positives are “unacceptable, panic ensues,” said Dr. Persing.
