Researchers describe viral shedding of monkeypox virus in patients to better understand the possible role of different bodily fluids in disease transmission

By Pooja Toshniwal PahariaReviewed by Danielle Ellis, B.Sc.Jul 20 2022

In a recent study published in Eurosurveillance, researchers described the shedding of the monkeypox (MPX) virus (MPXV) in Barcelona city of Spain.

Background

MPX was initially detected in the Democratic Republic of Congo in 1970, and a subsequent non-endemic MPX outbreak occurred in 2003 in the United States (US). Thereafter, MPX was considered an emerging infectious disease and a potential threat to public health. To date, MPX continues to expand globally, with >9,000 confirmed MPX cases reported across 57 nations by July 11, 2022.

From 2018 to 2021, seven cases were detected in the United Kingdom with MPXV deoxyribonucleic acid (DNA) detected in urine, blood, and nasopharyngeal samples. Additionally, four cases detected in Italy showed the presence of MPXV DNA in saliva, feces, and semen. The continual upsurge of MPX cases warrants a further understanding of MPXV shedding.

About the study

In the present study, researchers characterized MPX shedding to improve understanding of the potential role of body fluids in MPXV transmission.

The study was conducted between May and June 2022, for which 147 samples comprising saliva, rectal swabs, semen, nasopharyngeal swabs, urine, and feces were obtained from 12 MPXV-positive patients at 23 different time points by real-time polymerase chain reaction (PCR). In addition, Sanger sequencing was performed for the first three diagnosed MPX cases. Epidemiological and clinical data were retrieved from the patients’ medical records and were reviewed retrospectively.

Samples were obtained from two lesions for MPX diagnosis, and additionally, samples were screened for other sexually transmitted infections (STIs) by PCR: Mycoplasma genitalium, Chlamydia trachomatis, Neisseria gonorrhoeae and in the rectum, urine, and pharynx, respectively. In addition, serological screening was performed for Lymphogranuloma venereum, Treponema pallidum, and herpes virus in anal genital ulcers and human immunodeficiency virus (HIV), hepatitis B, and C viruses, and syphilis.

Results and discussion

All participants were young men who had sex with men (MSM), their median age was 38.5 years, most of them (nine patients) had prior STI history, and concurrent STIs were reported among three participants. All participants had active sex and had ≤10 sexual partners in the previous month, seven of which were taking HIV pre-exposure prophylaxis (PEP) medications.

 Five participants attended sex-on-premises or chemsex sessions, and three participants traveled within Spain, although none of them visited Madrid or Canary Islands, where MPXV transmission was initially detected in the country. Four participants had sex with confirmed cases of MPX, and four patients had received smallpox vaccination.

MPXV DNA was detected in saliva and skin lesion swabs of all (12/12) cases, with high viral loads [quantification cycle (Cq) values ranging between 16 and 21] in the skin pustules. In addition, MPXV DNA was detected in samples obtained between day 4 and day 16 following the onset of MPX symptoms.

Other samples were frequently MPXV-positive: nasopharyngeal swabs (10 cases), rectal swabs (11 cases), semen (seven cases), feces (eight cases), and urine (nine cases). Intermittent MPXV shedding (PCR-negative samples that became PCR-positive) was observed in the saliva and urine samples of two participants.

The study results are in accordance with previous studies reporting MPXV DNA detection in semen, blood, nasopharyngeal swabs, saliva, and feces. Of interest, saliva was previously tested only once in one patient. In the present study, MPXV DNA was detected in salivary samples of all patients obtained four to 16 days post symptom onset.

Conclusions

Overall, the study findings highlighted the routes of MPX transmission in Barcelona and enhanced knowledge of MPXV shedding. The study results could provide valuable information for MPX diagnostics and developing interventions for improved public health. However, further research must be conducted to determine MPXV’s capability to cause proctitis and several other unusual clinical manifestations.

In addition, future studies with larger sample sizes must further assess the infectivity of body fluids and their potential role in MPX transmission by close physical contact during sex. Further, data on smallpox vaccination history from large case series coupled with serological tests should be analyzed to improve knowledge of the beneficial role of smallpox vaccinations in protecting against MPXV infections. Furthermore, the frequency of asymptomatic and secondary cases must be assessed, and the impact of MPX on behavioral and social factors affecting MPX transmission must be evaluated.