At the beginning of May this year, health authorities in the UK raised the alarm over a spate of unexpected infections. Monkeypox, a disease most usually seen in West or Central African countries like Nigeria and the Democratic Republic of the Congo, has since spread to more than 500 people in the UK, with more cases turning up in at least 36 countries across the world.
The appearance of this poxvirus so far outside of its usual home is – and continues to be – mysterious, and so naturally, people started looking for explanations. And one thing was noticed pretty early on which seemed to hint at precisely that: the people contracting the virus were predominantly men who had sex with men. Could monkeypox be sexually transmitted?
Well – probably not, was the consensus of the scientific community. “It is probably too early to … assume that sexual activity was necessary for transmission, unless we have clear epidemiological data and analysis,” Michael Skinner, a reader in virology at Imperial College London, noted at the time.
“By nature, sexual activity involves intimate contact, which one would expect to increase the likelihood of transmission, whatever a person’s sexual orientation and irrespective of the mode of transmission,” he pointed out.
But this week, scientists in Italy and Germany reported detecting fragments of monkeypox DNA in the semen of infected patients, raising the possibility that perhaps the virus can be transmitted sexually after all. Is it time to upend the theories once again?
The answer to that is a pretty resounding “no” – at least, not yet. “It’s early days,” said Hugh Adler, Honorary Research Fellow in the Department of Clinical Sciences, Liverpool School of Tropical Medicine.
“Importantly the detection of viral DNA in semen does not itself alone constitute evidence of sexual transmissibility,” he added. “We already knew that monkeypox virus can be found in blood and urine – therefore it had the potential to be detected in genital secretions, either through sample contamination … or genuine viral spillover into genital secretions.”
But even if it does turn out to be true that monkeypox can be transmitted sexually, would it really make much difference?
“The whole question of whether the virus is in semen … as if it enables us to label hMPXV [monkeypox] as an STI and that this designation has particular importance is a distraction,” said David Tscharke, Professor of Immunology and Infectious Disease at the Australian National University, and a specialist in poxviruses.
“It also has no bearing on whether the virus in the current outbreaks has significantly changed its properties or mode of transmission,” he told IFLScience. “We do not know if this is typical of the hMPXV infections that have been occurring for decades in various countries in Africa, simply because no one has bothered to look.”
Of course, the more we know about the virus and its transmission methods, the better, and if the virus does turn out to be present in semen that would certainly be valuable information. It would help us understand the extent of the infection inside the body, Tscharke told IFLScience, and could inform future studies into transmission sites. But he stressed that the importance of the question is mostly limited to “an academic (and apparently social media) and somewhat semantic debate,” with the public health messaging – that the virus is spread through close contact, not necessarily sexual contact – being unchanged.
It's a message echoed by the World Health Organization (WHO). While they are investigating the reports from Italy and Germany in closer detail, the possibility that the virus is spread through semen “doesn't change our assessment of the current transmission route we are seeing at the moment, which is skin-to-skin contact, skin-to-mouth. That's what's driving the transmission,” said Catherine Smallwood, the monkeypox incident manager at the WHO Regional Office for Europe.
These early reports are certainly intriguing – but if living with COVID-19 has taught us anything, it’s that we shouldn’t get carried away with early and misleading narratives.
“It is imperative that public health messaging continues to appropriately highlight the role of close contact during sex in spread of the virus,” Tscharke told IFLScience. “But equally, labelling this as an STI might be counter-productive if it leads to people thinking that the only way the virus can be caught is through sexual activity.”
We know for sure that monkeypox can be transmitted through close contact with an infected person – and generally speaking, sexual contact falls under that category. “Even if monkeypox were not present in semen, we can confidently state it would be transmissible during sex anyway,” Adler pointed out, “since it is present in the skin rash … and likely can spread short distances via respiratory droplets.” There could be compelling evidence for the virus being transmitted sexually, he explained, such as patients becoming infected after having sex with someone no longer symptomatic – but so far, we just don’t have reports of this happening.
“For now, we don’t know if monkeypox can be transmitted sexually after the acute illness, and I am unaware of any public health reports to the contrary,” Adler concluded. “If data were to emerge suggesting sexual transmission from people who were otherwise asymptomatic, then we would have to look at our guidelines again.”
“For anyone having sex with a new partner, there are lots of reasons to practice safe sex and use condoms, regardless of whether monkeypox is in the mix or not.”