A day after the World Health Organization declared on Jan. 14 that no known cases of Ebola-virus transmission or active infection had been identified in West Africa for more than 42 days, the agency revealed the existence of a new, single case of Ebola-virus infection in Sierra Leone.

The appearance of the new case highlighted the challenges that remain in fully stamping out the West African Ebola–virus outbreak. The crisis began in December 2013, raged throughout 2014, and only wound down toward a sputtering halt near the end of 2015.

Dr. Peter Graaff (left) and Dr. Rick Brennan speaking at Jan. 14, 2016, press conference.

When Dr. Rick Brennan, the World Health Organization (WHO) director for Emergency Risk Management and Humanitarian Response, announced during a press conference on Jan. 14, “the end of Ebola-virus transmission in West Africa” and “the first time since 2014 that all know chains of transmission have stopped in Guinea, Liberia, and Sierra Leone,” he and his colleague, Dr. Peter Graaff, also underscored the ongoing risk for sporadic, isolated cases. The main threat for new cases comes from men who survived Ebola-virus infection but harbored significant quantities of infectious virus in various body fluids and tissues, including their semen, for a period of about 1 year following their infection.

During the press conference, both Dr. Brennan and Dr. Graaff spoke of a new, strengthened infrastructure that WHO had placed in West Africa to better monitor and react quickly to these flare-up cases – the mechanism that led to quick identification of the new Sierra Leone case.

“I think you’ll see a more responsive and effective WHO,” said Dr. Graaff, WHO’s director of Ebola response. “We will use the Ebola experience to be more agile, more operational, and better able to react more quickly to whatever future problems come our way,” including infectious-disease outbreaks by pathogens other than Ebola virus.

The 42-day period without new infections that had led to the announcement of an end to Ebola-virus transmission in West Africa represents two 21-day incubation cycles for the virus. Until the Sierra Leone case reported on Jan. 15, the last confirmed West African case had been identified in Liberia in mid-November. Liberia had previously been declared Ebola free in last May, but four new, isolated infections appeared subsequent to that transmitted by Ebola-infection survivors who still harbored infectious virus. Before the Jan. 15 case, an additional three such flare-ups occurred in Sierra Leone and another three in Guinea since last March, Dr. Brennan said.

CDC/Daniel J. DeNoon

The current tally on the West African Ebola outbreak stands at roughly 28,500 confirmed cases identified, and about 11,300 deaths. Nearly three-quarters of infections occurred during 2014. The case fatality rate at the start of the outbreak ran about 80%, noted Dr. Graaff, but gradually fell as infected patients began receiving better care. Near the outbreak’s end, the case fatality rate stood at roughly 35%, when most patients were receiving optimal clinical care.

WHO staffers are maintaining close surveillance of people who recently survived Ebola-virus infection so that they can identify and isolate any new infections. WHO personnel have also counseled these survivors on the risk they pose for potential transmission, primarily by unprotected sex by men for up to 12 months following the end of active infection. The WHO also plans to launch an investigational protocol to vaccinate sexual partners and other close contacts of adult male survivors with an as-yet unapproved Ebola vaccine to further reduce risk of new infections.

“The WHO and world community reacted slowly at the start of the Ebola outbreak” in early 2014, admitted Dr. Brennan. “Without question, the disease got away from us. In retrospect, there were a number of things that we should have done better and sooner,” he said. “We have done a lot of soul-searching and we [at WHO] have identified a number of weaknesses in our structures and systems. We have already taken several important steps, and we are undergoing major reforms of our emergency operations. I think you’ll see a much more effective WHO in the future.”

Reform of WHO systems for infection prevention and control “will be much better able to detect new cases, not only of Ebola, but of other important diseases,” said Dr. Graaff.

The United States is also strengthening its health screening and monitoring system for travelers coming from affected countries and improving its hospital preparedness to manage cases, said Alice C. Hill, senior adviser for preparedness and resilience at the National Security Council and special assistant to President Obama. Hill, who spoke Jan. 6 at the Public Health Emergency Medical Countermeasures Enterprise stakeholders workshop, acknowledged that challenges still exist that must be addressed, including the development of safe and effective diagnostics, treatments, and vaccines for existing infectious diseases such as influenza and more emerging threats such as Ebola or MERS (Middle East Respiratory Syndrome), developing accurate disease forecasting capabilities to predict what will be the next threat, building rapid clinical trial networks and manufacturing capabilities, and the abilities for mass dispensing of medical countermeasures.

Gregory Twachtman also contributed to this story.

mzoler@frontlinemedcom.com

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West African Ebola–virus transmission ends, then resumes