LONDON – One month in, and the World Health Organization (WHO) is cautiously optimistic that the Ebola virus outbreak threatening the city of Mbandaka in the Democratic Republic of Congo (DRC) has been contained by the ring vaccination program that was started on May 21, 2018.

There also is cautious optimism about Bikoro, one of two rural areas involved in the outbreak. However, there remain concerns about Iboka, described as one of the most remote areas on earth, where a new case was confirmed on June 7, 2018.

There has been very good progress in the response to the outbreak, particularly in Mbandaka and Bikoro, said Peter Salama, WHO's deputy director general for emergency preparedness and response.

The last confirmed cases in these two places were in the middle of May. "We have reached more than 98 percent of contacts with vaccinations and the majority were [vaccinated] more than 10 days ago, so we think they are protected," Salama said, in a briefing after returning from a visit to DRC to assess progress last week.

The focus of the response has now shifted to rural, isolated areas, which as well as being remote, are heavily forested. "It's not even territory that can be traversed with four-wheel drive vehicles; it's motorcycles only," said Salama.

WHO still needs to strengthen its operational base. It has 80 people on the ground at a treatment center in Iboko, who currently are having to sleep 15 to 20 to a tent.

"It's an enormous logistical effort to reach every alert of a case and then every contact of a case," said Salama.

With a new case confirmed on Thursday June 7, "there is still a lot of tough work to do," Salama said. "We learnt the hard way in the past, not to underestimate Ebola."

WHO's epidemiological data tracking the chains of transmission, show different chains are inter-related and can become self-propagating. One single case, an infected nurse, led to many contacts contracting the virus.

"That's why we always need to be concerned about a single case becoming a 'super-spreader' – it only takes one case to result in an upsurge of cases," said Salama.

As of June 6, there were 38 confirmed cases, 14 probable cases and 10 suspected cases in DRC. There have been 27 deaths.

A range of treatments available

On June 4, an ethics committee in DRC approved the use of five experimental Ebola therapies on a compassionate use/expanded access basis. This will be the first time a range of treatments has been available during an Ebola outbreak.

Four of the five drugs, Mapp Biopharmaceuticals Inc.'s Zmapp, Gilead Sciences Inc.'s remdesivir (GS-5734), REGN-3470-3471-3479 from Regeneron Pharmaceutical Inc., and Mab114 (VRC-EBOMAB092-00-AB), which is being developed by the U.S. National Institutes of Health Vaccine Research Center, are in DRC and ready to use.

WHO is arranging for supplies of the fifth, Toyama Chemical Co. Ltd.'s favipiravir. However, independent experts convened by WHO on May 17 to evaluate which experimental therapies should be considered for use in the DRC outbreak were circumspect about the product.

Favipiravir was tested in a single arm proof-of-concept trial that took place in four treatment centers in Guinea during the West Africa epidemic of 2014-2015. The study, which recruited 126 patients, showed the drug was well-tolerated, but did not show high efficacy in treating Ebola.

Tokyo-based Toyama has approval for the product as a treatment for influenza under the brand name Avigan and the decision to test it against Ebola was based on data showing it to be effective in mouse models of the infection.

Based on the available data, the WHO expert group said there is "considerable uncertainty" as to whether favipiravir provides benefits for patients with Ebola infection. Favipiravir may be considered in select circumstances where ZMapp, remdesivir or REGN 3470-3471-3479 are not available.

Salama was unable to confirm if any Ebola patients had yet received any of the four drugs. But he said, he was sure there would be a discussion going on among clinicians treating the most recently diagnosed case about what would be the most appropriate treatment.

Since the launch of the vaccination program on May 21, a total of 1,199 people have been immunized with Merck and Co. Inc.'s rVSV-Zebov vaccine.

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