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Monkeypox may be sexually transmitted in humans

New research highlights the potential for sexual transmission of monkeypox in humans. The 2022 monkeypox outbreak has been linked to sexual contact in patients through direct contact with bodily fluids and skin lesions. Understanding the biology of monkeypox infection of the testes has substantial public health implications.

Investigators at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) analyzed tissue samples from crab-eating macaques, which serve as a primate model for studying the disease and the efficacy of vaccines and treatments against monkeypox.

“We examined tissue samples obtained during both the acute phase of the disease, when infection is at its peak, and the convalescent phase, when infection is gradually subsiding,” explained study senior author Dr. Xiankun (Kevin) Zeng. “We detected monkeypox virus in interstitial cells and seminiferous tubules of the testes, as well as the epididymal lumina, which are the sites of sperm production and maturation.”

The team also found evidence of persistent monkeypox infection in two macaques that survived the virus. While the virus cleared from most organs, it could be detected for up to 37 days post-exposure in the testes.

The USAMRIID team had previously demonstrated that other viruses, including Ebola, can persist in the organs of primates where the immune system is suppressed. Similar to humans, these immune privileged sites include the eyes, brain, and testes.

“Our data provide evidence that monkeypox virus may be shed into semen during both acute and convalescent stages of the disease in crab-eating macaques,” said Dr. Zeng. “It seems plausible, therefore, that human transmission in convalescent male patients might occur via semen.” 

Further studies are needed to understand the origins and implications of viral DNA shed in semen, as well as to confirm whether semen from monkeypox patients contains infectious virus. 

The researchers noted that the macaque model may not fully reflect monkeypox in humans. This is because the animals demonstrate a more severe disease than in humans.  The incubation period in animals is also shorter. 

The study is published in the journal Nature Microbiology.

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By Katherine Bucko, Staff Writer

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