This story is part of a partnership between MedPage Today and VICE News.

Preliminary study results published today show what public health experts have feared for months: the Ebola virus can linger in semen long after patients recover from its life-threatening symptoms.

Semen samples from several recovered Ebola patients in Sierra Leone tested positive for virus fragments up to nine months after onset of the virus, according to a report published in the New England Journal of Medicine today.

"The main message from these papers is that long after the Ebola outbreaks end, the survivors and their partners and families will still face and be dealing with huge challenges, requiring strong national and international support for the next 6-12 months," WHO spokeswoman Margaret Harris said, adding that the affected countries are working to make sure survivors know the virus can linger and provide them with condoms and testing.

Dr. Gibrilla Fadlu Deen, of Connaught Hospital in Freetown, Sierra Leone, and his team enrolled 100 male Ebola survivors over 18-years-old who had been diagnosed with Ebola between two and 10 months prior to launch of the study, and 93 of them were included in the analysis. Deen and his team found that 11 of the 43 who were tested between seven and nine months after Ebola onset (26 percent) still had detectable levels of the virus in their semen.

"That's critical because the patient is otherwise well and is going to resume normal activities including sexual intimacies with partners," said Dr. William Schaffner, chair of preventive medicine at Vanderbilt University, who was not involved in the study. "That can set up transmission of the virus and set up a new chain of transmissions. That's the time bomb that's ticking."

Ebola survivors' semen also tested positive for Ebola between two and three months after onset (nine of nine, or 100 percent), and between four and six months after onset (26 of 40, or 65 percent). The one man who provided a semen sample to researchers 10 months after Ebola onset had "indeterminate" results.

Until men who have survived Ebola have had two negative semen test results, they should abstain from sexual activity or use condoms, the Centers for Disease Control and Prevention (CDC) said in a statement today. Health officials also recommended washing hands after they've had contact with Ebola survivors' semen. Harris said everyone discharged from Ebola treatment units has been given a supply of as many as 90 condoms, but this number can vary from unit to unit.

However, Deen and his team acknowledge in their study that there have been fewer than 20 suspected cases of sexually transmitted Ebola cases reported.

Although sexual transmission of Ebola is considered rare, a 44-year-old Liberian woman was diagnosed with Ebola in March, a few weeks after having unprotected vaginal intercourse with a man who survived the virus the previous fall, according to a supplemental case report published in NEJM. Health workers determined that the woman had 192 other contacts, but none of them had clinical signs of Ebola.

The woman died on March 27, but the Ebola survivor with whom she'd had intercourse provided blood and semen samples to health workers. Although the man's blood tested negative for Ebola, his semen tested positive for the virus's RNA, or genetic code, according to the report.

As of October 11, there have been 28,454 reported Ebola cases in Guinea, Liberia, and Sierra Leone, including 11,297 deaths, according to the World Health Organization (WHO). The West African Ebola outbreak, which began in March 2014 is considered the largest Ebola outbreak in history.

"We had thought initially that once the patient had recovered, they had recovered and that was the end of it," said Schaffner, a former president of the National Foundation for Infectious Diseases.

But because of the size and duration of this outbreak, public health workers have been made aware of post-Ebola symptoms, which include arthritis in the lower back and hips, central nervous system problems and forgetfulness, Schaffner said. The virus can also survive in parts of the body that are protected from the immune system: the eye and the testicles.

One of Schaffner's former students, Dr. Ian Crozier, who contracted Ebola while working as a WHO volunteer in Sierra Leone and was treated at Emory University in Atlanta, authored a study and spoke to the New York Times earlier this year about how the virus survived in his eye and turned it from blue to green.

This week, a nurse in the UK was hospitalized with symptoms attributed to post Ebola syndrome and listed in critical condition, according to the BBC.

Of the 881 health workers who contracted the virus as part of the West African outbreak, 513 have died, according to WHO.

There have been five new confirmed Ebola cases per week or fewer for the past 11 weeks, according to the latest WHO Ebola situation report. There have been no new confirmed Ebola cases for the past two weeks in West Africa, but there are 150 patient contacts still under follow-up in Guinea with 118 at high risk for contracting the virus. There are also 259 contacts that have been identified but not traced.