1 INTRODUCTION

Monkeypox virus (MPXV) human-to-human transmission occurs through close contact with respiratory droplets, skin and mucosal lesions, and body fluids of infected people.¹ As of September 2022, more than 61 000 MPX cases have been reported in more than 50 countries,² with the majority of cases diagnosed in men who have sex with men. The nearly exclusive spread within this community and the predominant clinical involvement of the anal/genital region with lesions, along with the detection of the virus in semen, anal, and urethral secretions led to the hypothesis of a sexual transmission, as previously suggested: the 2017 outbreak in Nigeria involved many young adult males who experienced genital lesions, concomitant syphilis, and HIV infection.^{3, 4} Unprotected sexual intercourse and recent history of multiple partners are thus believed to facilitate MPXV transmission.⁵ Recently, a large case series, that included 528 MPX patients from the current outbreak, identified sexual activity as the most frequently suspected route of transmission.⁶ Supporting this thesis, one or more concomitant sexually transmitted infections (STIs) (e.g., Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, Trichomonas vaginalis, or HIV) have often been documented in MPX patients.^{7, 8}

In this study, we investigated the presence of STIs in patients evaluated for suspect MPX infection, regardless to the presence of symptoms.

2 MATERIALS AND METHODS

Patients with papular-vesicular rash compatible with human MPX, attending our sexual health clinic from May 23 to September 5, 2022 were tested for MPXV and screened for STIs, even when asymptomatic. Along with epidemiological and clinical history (including HIV, HCV, HBV, and Treponema pallidum previous infection), oropharyngeal, urethral, and anal swabs were collected and tested for both MPXV and STIs. The study was conducted in the framework of clinical protocol on MPXV monitoring; all subjects provided written informed consent. The presence of MPXV DNA was investigated also in plasma and skin lesions. Nucleic acids were extracted by means of QIAsymphony SP instrument (Qiagen) and the Real-Time PCR RealStar® Orthopoxvirus PCR Kit 1.0 (Altona Diagnotics), targeting Orthopoxvirus genome, was used as screening assay, confirming the presence of MPXV DNA with Monkeypox Virus Real Time PCR Kit (Bioperfectus). C. trachomatis, N. gonorrhoeae, M. genitalium, and T. vaginalis presence was investigated by means of STI PLUS ELITe MGB® Kit on InGenius® platform (ELITechGroup).

3 RESULTS

A total of 49 patients were tested. MPXV infection was confirmed in 32 (65%) patients (Table 1), while at least 1 STI-related pathogen was found in 15 (31%) subjects, with an overall coinfection rate of 20% (N = 10). M. genitalium and N. gonorrhoeae were the most frequent STIs in the coinfected patients (50% and 40%, respectively) and C. trachomatis the main 1 in absence of MPXV (4/5 patients). Features of the MPXV-STI coinfection are resumed in Table 2. Patients 1, 3, and 6 reported a previous infection with N. gonorrhoeae, while subjects 1, 2, 5, 6, 8, and 9 had a confirmed history of syphilis. In addition, 4 individuals were known PLWH (people living with HIV) on ART with controlled viremia. Patients 5, 8, and 10 tested positive for HBcAb and HBsAb, and negative for HBsAg (Table 3). Interestingly, N. gonorrhoeae and M. genitalium were the most frequent STIs in 648 patients with no clinical evidence of MPX and routinely tested solely for STIs in the same period (49% and 37% of cases, respectively).

4 DISCUSSION

Concomitant STIs were frequent in our MPX patients, in line with previously reported results.⁹ N. gonorrhoeae and M. genitalium were the most frequent infections in both MPX patients and in those tested only for STIs. Our results about gonorrhoea confirm World Health Organization (WHO) observation, being the second most common sexually transmitted infectious disease in the world.¹⁰ The detection of M. genitalium, common in patients with non-chlamydial non-gonococcal urethritis, was higher than expected. However, it must be noted that M. genitalium can be often asymptomatic, thus its prevalence might be underestimated, particularly in patients not regularly attending sexual health clinic.¹¹

Urethral, rectal and pharyngeal are the recommended specimens to collect for STIs screening¹² while limited data are available on their usefulness in the context of MPXV diagnosis, as for WHO recommendation on using skin lesion specimen.¹³ In a previous study we reported the presence of replicant MPXV in anal and urethral swabs³: similarly, 9/10 and 5/10 of our patients resulted positive for MPXV in rectum and urethra, respectively. If confirmed by further studies and convenient to the epidemiological contest, the same anogenital swabs might be considered as a screening tool for both MPXV and STIs: such evidence could also drive the development of multiplex diagnostic assays, requiring a single specimen collection.

The prevalence of STIs among MPX cases confirms that this population is sexually active and recently got engaged in sexual close contact. The proportion of the bacterial infectious agents are similar in MPX and general population, attesting the representativity of the sample in our case mix, although limited in numbers. Further larger studies are encouraged to verify the observation that MPX patients appear not to be at higher risk for sexually transmitted diseases.

We still recognize that our study has three main limitations: the limited size of the sample; no systematic longitudinal testing for STIs after MPX diagnosis; STIs testing on those patients suspected for MPX (n = 49) was performed only on a clinical basis, while the group tested only for STIs (n = 648) includes both symptomatic and asymptomatic patients.

Despite the limitations, our data from coinfected patients suggest that MPXV and STIs may share the same route of inoculum, corroborating the hypothesis of possible sexual transmission for the emerging poxvirus. Also, Thornhill et al.⁶ recommended consideration of MPX in persons presenting with traditional STI symptoms. Since MPX and STIs might masquerade each other, with our findings, we reinforce the following indications: (1) MPX patients should be screened for STIs as it should be done for any other sexually transmitted pathogen, without the stigmatizing misconception of an implied higher-risk behavior (2) STI patients should be tested for MPXV as well, despite the presence of specific skin lesion, as reported in a retrospective study by De Baetselier et al.¹⁴ Like other infectious diseases, MPX is a public health issue that involves all people, all people might acquire it.¹⁵ Since there must not be shame about current STIs, considering MPXV a sexually transmitted pathogen could make more people to get tested, just like they do for any other STI.

AUTHOR CONTRIBUTIONS

Alberto Rizzo and Federica Salari contributed to writing the article. Amedeo Capetti, Giacomo Pozza and Andrea Giacomelli visited the individuals. Davide Mileto and Alessandro Mancon contributed to the reviewing of the article. Gloria Gagliardi and Bianchi Micol performed microbiological assays. Maria Vittoria Cossu, Spinello Antinori, and Pietro Olivieri coordinated clinical activities. Valeria Micheli, Maria Rita Gismondo and Alessandra Lombardi coordinated laboratory activities. All authors have read and agreed to the published version of the manuscript.

CONFLICT OF INTEREST

The authors declare no conflict of interest.

ETHICS STATEMENT

Approval on monkeypox study activity from local institution: Comitato Etico Milano Area 1, protocol number n. 2022/ST/124. All subjects provided written informed consent.