Story highlights Preliminary study finds virus fragments can persist in semen of survivors at least nine months

Study follows case of nurse's apparently relapse in Britain

Earlier this year, supposedly cured doctor found virus still lurking in eyes

(CNN) The Ebola virus is craftier and more persistent than had been thought, a new study has found, adding a fresh layer of worry over how to eradicate the virus and mitigate the threat.

A new study by the World Health Organization has found that the disappearance of Ebola symptoms does not mean the virus is gone. Far from it.

Instead, the preliminary study discovered that the virus can still be found in the semen of survivors for at least nine months after the onset of symptoms.

The study only adds to concerns about the persistence of the virus, and its potential to be transmitted, in people previously thought to have been cured.

Those thought cured can still carry virus

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