Investigation finds evidence sexual transmission of Ebola sparked new outbreak in Guinea more than a year after survivor’s recovery

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Persisting virus in survivor’s semen apparently remained infectious 470 days after symptoms began

Case underscores value of enhanced surveillance, improved diagnostic, care and outbreak response capacities, authors say

The Ebola outbreak in Guinea had been declared over in December 2015, more than three months earlier, this last March when health officials investigating three recent deaths in N’Zérékoré, the district that is home to the nation’s second largest city, uncovered a new outbreak of the virus that had spread through a family and into neighboring Liberia.

N’Zérékoré is in the forest region of the country, where the epidemic that swept through West Africa had begun in December 2013, when a child caught the virus from a fruit bat, and authorities wondered if that had happened again. Either that, they reasoned, or a chain of transmission among humans had continued, and somehow gone unnoticed for several months. But tests of blood collected from the new patients found the form of the virus that had last been detected in 2014, the first year of the epidemic. That meant it wasn’t the result of a new animal to human transmission. And because the virus had continued to mutate over the course of the epidemic, it also meant the current outbreak wasn’t likely to have been the result of ongoing transmission.

A closer examination found the nearest match for the virus causing illnesses in March 2016 had been collected in a diagnostic test for a man who had been treated in a neighboring Gueckedou Ebola treatment center in November 2014. He had survived, and adhered to instructions to abstain from sex for the next nine months. Then in January 2016, he had sex with a man who had subsequently fallen sick with Ebola.

That man, a separate investigation tracing contacts of patients in the current outbreak had by then found, was “Case 1” the first patient among them. Semen collected from the man who had recovered in Nov. 2014 confirmed it still carried virus that was infectious, and that was identical to that causing illness in March 2016, more than 470 days later.

Authors of an article detailing the investigation released this week in Clinical Infectious Diseases note that prior to this case the longest period between a patient’s illness onset and confirmed sexual transmission of the virus had been 179 days. While saying that they can’t rule out the possibility that the November 2014 survivor was “silently reinfected,” they add that seems unlikely as no such cases have previously been confirmed. The case highlights both the need to further examine the persistence of transmissable virus in semen, and the value of resources that have enabled improved case detection, monitoring, and responses.

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