People around the world are still contracting monkeypox – including in Germany. It is therefore important to know how the virus is transmitted from person to person. Now there are indications of a previously undisclosed transmission route.
The causative agents of monkeypox are also found in the testicles and semen of infected monkeys. This is what researchers led by Jun Liu from the US Army Medical Research Institute of Infectious Diseases (USAMRIID) in Fort Detrick found out. The results of their investigations, which were published in the journal “Nature Microbiology”, indicate that the monkeypox virus can also be transmitted sexually to humans.
Until now, it was assumed that monkeypox was not a sexually transmitted infection. Transmission has been limited to close physical contact between people, through airborne droplets, but also through contact with the clothing, bedding, towels and eating utensils of a person who has contracted monkeypox. Infection through semen or vaginal secretions was only considered possible, but has not yet been proven. The results of the USAMRIID researchers now provide further evidence that people can also be infected directly through sex.
For the study, the research team examined testicular tissue from 21 long-tailed macaques (Macaca fascicularis) infected with the virus at different stages of the disease. “We examined tissue samples taken both during the acute phase of the disease and during the convalescent phase, i.e. when the infection gradually subsides,” explains Xiankun Zeng, who was also involved in the study, according to the institute’s statement.
The research team found monkeypox antigens in 18 of the 21 tissue samples. Evidence of monkeypox has also been found in cells and seminiferous tubules associated with sperm production and maturation. The researchers also saw that while the viruses were no longer detectable in most organs and even in healed skin lesions during convalescence, the pathogens were still present in the testicles of the macaques up to 37 days after infection.
“Our data show that monkeypox virus can be shed in the semen of macaques during both the acute and convalescent phases of the disease,” said Zeng. “It therefore seems plausible that transmission to humans in convalescent male patients could also occur via the sperm,” says Zeng. Even when the infected people feel healthy again and no longer have skin lesions. The researchers can imagine that the immune system is the reason for this. They were able to show in previous studies that the pathogens of Ebola, Marburg, Nipah and Crimean Congo fever can persist in certain organs of primates. These include the eyes, the brain – and the testicles. These organs are only partially accessible to the immune system.
However, further studies are urgently needed to be able to say with certainty whether the semen of infected individuals also leads to human-to-human transmission of the monkeypox virus, particularly after the skin lesions have healed. However, one thing is certain: monkeypox has the potential to become a sexually transmitted disease.
