A study from France is raising questions about whether monkeypox can be transmitted asymptomatically, after researchers collected anorectal swabs from 200 men who have sex with men – all having routine STD testing – tested them for monkeypox, and despite no symptoms, found 13 were positive.
Critically, none had a single monkeypox symptom when their tests were conducted, nor did they have any tell-tale early signs of infection – no lesions, no fever, no swollen lymph nodes, reports Business Insider SA.
That doesn’t necessarily mean that those 13 men were capable of spreading monkeypox without knowing it, but it does raise the question: is asymptomatic transmission of monkeypox possible?
‘Body weakness’ as a potential early sign of monkeypox, before a rash emerges
The question of asymptomatic transmission during sex is also one that Nigerian Dr Dimie Ogoina – who was one of the very first clinicians to raise the alarm about high numbers of young and active men contracting monkeypox back in 2017 – has been asking himself.
Ogoina, medical director at Niger Delta University Teaching Hospital, told Insider he recently saw a monkeypox patient in his clinic who said that “when they had a sexual relationship, there was no ulcer, no rash” and no fever, they only felt some “body weakness.
It was only “after the sexual relationship that he noticed a genital rash”, Ogoina said. Then, five days later, his sexual partner also noticed a rash.
Can monkeypox transmit via semen?
It’s unclear whether monkeypox can be transmitted asymptomatically, perhaps via bodily fluids, and before people start feeling sick, but some have already shown the virus can be detected in some infected people’s semen.
“It’s not necessarily unusual to see viral particles in body fluids – it doesn’t mean they are replication competent, able to cause disease,” Ogoina added. “But I think it’s also a signal we need to deeply explore.”
As is the case with COVID-19, a positive PCR test doesn’t necessarily mean a person is infectious, either.
Dr Lawrence Purpura, an infectious disease expert at Columbia University Irving Medical Centre, studies how viruses transmit in semen. For some diseases (like Ebola) it’s pretty clear that semen plays a role in transmission, while for others (like COVID) there’s almost no evidence of that.
“Detecting monkeypox virus in semen is not entirely surprising,” Purpura has said previously. “First you want to ask: is the detected virus viable and infectious?”
The “gold standard” for answering the question properly, he says, is “not just detect using PCR, but trying to grow the virus in a laboratory”.
“And this is called virus isolation.”
The research, published in the Annals of Internal Medicine, is still careful to emphasise that it’s yet unknown whether monkeypox can transmit asymptomatically.
But they said it would have huge implications.
If monkeypox is spreading from some people without any symptoms, vaccinating only those who are exposed to a known case isn’t enough to stop the outbreak.
After five years of sounding the alarm on monkeypox, Ogoina is well aware there are plenty of mysteries left to unravel about how this virus spreads.
“There are a lot of things that are still not known about monkeypox: the natural history is not well described, because, of course, it has been a neglected disease,” he said. He’s hopeful that with more of the world’s attention – and resources – trained on the problem, better answers will surface.
“Since the global north is now having cases, I’m sure there will be investments in research,” he added.
“If we’re able to, for instance, show that viable viruses can be isolated from the semen and it lingers for a while, then it completely transforms the type of public advice we need to give, and how we look at transmission.”
And if it were the case that monkeypox can spread without symptoms, “it changes everything”, he said.
Study details
Detection of Monkeypox Virus in Anorectal Swabs From Asymptomatic Men Who Have Sex With Men in a Sexually Transmitted Infection Screening Program in Paris, France
Valentine Marie Ferré, Antoine Bachelard, Meryem Zaidi, et al.
Published in Annals of Internal Medicine on 16 August 2022
Background
A monkeypox virus (MPXV) outbreak emerged in May 2022, affecting mostly men who have sex with men (MSM). Although most infections were characterized by cutaneous lesions, a recent report described 3 asymptomatic men with no cutaneous lesions but with positive results on anorectal MPXV polymerase chain reaction (PCR) testing (1). Determining whether MPXV infection can be asymptomatic may better inform epidemic management.
Objective
To assess the presence of MPXV in anorectal samples among asymptomatic MSM routinely tested for bacterial sexually transmitted infections (2).
Methods and Findings
We retrospectively performed testing for MPXV on all anorectal swabs that were collected in our centre as part of a screening program for Neisseria gonorrhoeae and Chlamydia trachomatis. Per French guidelines, this screening is performed every three months among MSM with multiple sexual partners who are either taking HIV preexposure prophylaxis (PrEP) or living with HIV and receiving antiretroviral treatment. Patients could have urine samples and anal swabs collected at our clinic or a private laboratory. After the first case of MPXV infection was identified in France on 19 May 2022, screening was halted in patients who had lesions suspicious for MPXV. We report on asymptomatic MSM who tested negative for N gonorrhoeae and C trachomatis on MPXV anal swabs collected at the Infectious Disease Department and the Sexual Health Clinic of Bichat-Claude Bernard Hospital in Paris from 5 June to 11 July 2022. All participants attended a clinical visit on the day of sampling as part of routine PrEP or HIV treatment follow-up. Participants gave written informed consent to have their data recorded in Nadis, an electronic medical record designed for follow-up of persons living with HIV or receiving HIV PrEP and use of their data for research. The local review board did not require specific consent to use remnant routine biological samples in the setting of the MPXV epidemic.
After heat inactivation (12 minutes at 70 °C), nucleic acids were extracted using a STARMag 96 X 4 Universal Cartridge Kit (Seegene) on the MICROLAB NIMBUS system (Seegene). MPXV-specific PCR was performed using a previously published protocol.
During the study period, 706 MSM visited our clinic, 383 had symptoms suggestive of MPXV infection (40% had anal lesions), and MPXV infection was confirmed in 271 of those with symptoms. Screening for C trachomatis and N gonorrhoeae infection was not performed when MPXV infection was suspected because of laboratory biosafety restrictions. Of the 706 MSM, 323 had no MPXV symptoms, and 213 had anal swabs collected and were negative for C trachomatis and N gonorrhoeae . Among these 213 MSM, the median age was 38 years (IQR, 29 to 48 years), and 110 (52%) were living with HIV and receiving antiretroviral therapy, with a median of 9 years (IQR, 4 to 18 years) since diagnosis. Among those with HIV, 78% had undetectable viral load (median viral load was 74 copies/mL [IQR, 37 to 2270 copies/mL] in the others), and the median last CD4 T-cell count was 0.766 × 109 cells/L (IQR, 0.560 to 1.001 × 109 cells/L).
MPXV PCR was successfully performed on 200 of 213 anal swabs and was positive in 13 (6.5%). Of those testing positive, 8 were living with HIV; all had undetectable HIV-1 viral load, and all had a CD4 T-cell count above 0.500 × 109 cells/L, except 1 who had a CD4 T-cell count of 0.123 × 109 cells/L. We contacted all 13 MPXV-positive participants who were initially asymptomatic to assess symptom status and advised them to limit sexual activity for 21 days after the test date and to notify their recent sexual partners. None reported symptoms suggestive of MPXV infection, but 2 subsequently presented to our clinic with symptoms. One had a cycle threshold (Ct) value of 20.7 on PCR of the sample taken during the asymptomatic stage and a Ct value of 33.0 seven days later, when he presented with anal rash. The other presented with pharyngitis and fever but no anal symptoms; PCR on the anal swab taken during the asymptomatic phase showed a Ct value of 38.2, and PCR on a pharyngeal swab 9 days later showed a Ct value of 24.
Of the 187 asymptomatic participants who tested negative for MPXV, 3 presented to our clinic more than 3 weeks after the initial MPXV-negative anal swab with symptoms suggestive of MPXV infection and tested positive.
Discussion
This report documents positive MPXV PCR results from anal samples in asymptomatic MSM. Whether this indicates viral shedding that can lead to transmission is unknown. If so, the practice of ring postexposure vaccination around symptomatic persons with probable or confirmed MPXV infection may not be sufficient to contain spread. Recent French recommendations have advised vaccination for all MSM with multiple partners.
See more from MedicalBrief archives:
Fauci says monkeypox spread ‘very reminiscent’ of early days of HIV
WHO declares monkeypox a global health emergency
Monkeypox: forecasters predict the global outlook for 2022