Health officials have begun warning survivors of the Ebola virus against having unprotected sex after the virus was found in a male survivor's semen 175 days after he first developed symptoms of the virus, which it noted was 74 days longer than it has been found in other survivors.

The Centers for Disease Control and Prevention has previously stated as a part of its transmission guidelines that people should wait approximately three months after recovery before engaging in unprotected sexual activity. However, in light of this new development, they are now saying that "because sexual transmission of Ebola cannot be ruled out, Ebola survivors should not have sex (oral, vaginal, or anal) until more information becomes available." The CDC recommends that those who do choose to have sex use a condom.

According to the latest figures from the CDC, Guinea, Liberia and Sierra Leone, the countries in Africa that were most affected by the outbreak that began in 2014, have seen more than 25,500 likely cases that have resulted in more than 10,000 deaths.

Though the number of infections have dropped significantly, the World Health Organization still recently called it an international emergency.

Thus far, the information is consistent with sexual transmission, according to scientists. But it is not conclusive and they continue to study the possibility of sexual transmission. While scientists believe it is rare for the virus to be transmitted in this manner, it "cannot be ruled out," the CDC said. Researchers at the CDC are trying to determine if the sample provided by the man actually contained the infectious virus, harmless genetic material or RNA.

The World Health Organization is planning to study the survivors in an attempt to establish the range of time that various body fluids such as semen, urine and breast milk tend to contain Ebola even after it has been cleared from the bloodstream.

"The problem is we haven't looked at a large number of cases," said Stuart Nichol, an Ebola researcher at the C.D.C. Philip Ireland, a Liberian doctor who contracted Ebola while working last summer at John F. Kennedy Medical Center in Monrovia, the capital, said that despite the practical difficulty involved in collecting semen samples, all survivors should be offered the chance to know whether their body fluids still contain traces of Ebola. "Tests have to be made available, and have to be made next-to-free," he said.

Dr. Bruce Aylward, the lead Ebola official at the W.H.O., said the agency was exploring the feasibility of just such a program. "It's a smart thing to do," he said.