WHO emergencies chief Dr. Michael Ryan told reporters in Geneva that disease surveillance has improved even as the number of attacks against health workers rose three-fold over the last five months. Five health workers have died since the outbreak began in August.
"We've also managed to improve surveillance performance in terms of the proportion of cases coming off contact lists," he said. Disease transmission has "decreased significantly" over the last couple of weeks in the epicenters of Butembo and Katwa though challenges remain there, he added.
Doctors Without Borders, which pulled out of Ebola treatment centers in Butembo and Katwa earlier this year because of the violence, said contact tracing is still too low. "As few as 32 percent of the new confirmed cases were linked back to known contacts," the group said in a statement. "This means that the listing of contacts and surveillance are not effective. Contact tracing is essential to control the evolution of the outbreak."
More than 1,200 people have now died in the second-deadliest Ebola outbreak in history. Virus containment efforts are particularly challenging because the highly volatile security situation makes it too dangerous for surveillance teams to access some areas.
The real number of Ebola cases is "likely to be even higher" because of the difficulties in tracing cases, Doctors Without Borders said. The disease is spread mainly through contact with the bodily fluids of Ebola patients and victims. In an effort to contain the virus, health workers monitor those who are known to have come into contact with an Ebola patient for a period of 21 days.
If new cases haven't previously been identified as possible contacts by outbreak responders that suggests authorities have little idea where the virus is spreading. The violence also has kept workers from being able to vaccinate people in some communities.
Larson reported from Dakar, Senegal.
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