The main semen is a virus reservoir.

Scientists point out that semen can contain more than 27 viruses including Ebola, HIV and herpes virus.

Semen is a favorable environment for viruses , NPR reports in Emerging Infectious Diseases.

Scientists from Oxford University (UK) analyzed more than 3,800 works, found that at least 27 viruses can exist in semen including Ebola, chikungunya, Lassa, herpes and HIV. Most of them appear temporarily after a person is infected, some cases exist for many years.

The testicles are not under the control of the immune system, making them an ideal place for virus to stay.(Photo: NPR).

"This finding shows that semen contains genetic or viral proteins , " said lead researcher Alex Salam. However, he insisted this did not prove that all viruses were sexually transmitted.

Regarding the reason the virus exists in semen, Dr. Amesh Adalja from John Hopkins Hospital (USA) explains that male testes are "prioritized" in particular, not under the control of the immune system, so they become a reason ideal for viruses to hide.

Dr. Adalja identified the next step to do is to determine the ability to develop, reproduce in semen medium as well as the risk of transmission through sex of viruses. This result will bring great significance to disease prevention. In fact, amid the Zika outbreak in the Americas, thanks to early detection of sexually transmitted viruses, people were promptly recommended to use condoms or abstain from sex.

In addition, if the virus stays in the semen for too long, even if it is suppressed, it can still come back again due to unprotected sex like the Ebola case. Scientists have noted that an African man still has the Ebola virus in his semen after a year and a half of the disease.