Transmission characteristics, replication patterns and clinical manifestations of human monkeypox virus—an in-depth analysis of four cases from Germany

OBJECTIVE: Since April 2022, increasing numbers of monkeypox (MPX) cases have been reported outside endemic areas as part of an international outbreak. Our study shows aspects of clinical manifestations as well as epidemiological and virological features impacting transmission, for which only scarce data are available so far. METHODS: We present a descriptive study consisting of epidemiological, clinical and virological data of four patients with confirmed MPX diagnosis. Follow-up examinations included in-depth virological investigations, including MPX virus-specific quantitative PCR and virus isolation. RESULTS: Between 22 May 2022, and 21 June 2022, four patients with MPX were evaluated. The number of lesions ranged between one and more than 30, with asynchronous eruptions. The periorificial distribution of initial lesions together with the case histories strongly suggest human-to-human transmission during intimate contacts in sexual activities. None of the patients reported about memorable lesions on the skin of potential risk contacts. Virological sampling showed positive MPX virus-specific quantitative PCR results from swabs of the primary lesions (until day 22 after symptom onset), pharyngeal and anal mucosa, urine, seminal fluid, blood and samples of non-affected skin. Virus isolation was positive in 6/14 samples (lesional skin, anal and pharyngeal mucosa). One patient required inpatient treatment for bacterial superinfection; in another patient, three sexually transmitted co-infections were present. CONCLUSIONS: Our report demonstrates asynchronous multiple-site lesions of MPX with prolonged PCR positivity in mucosal swabs, swabs of non-affected skin, urine and seminal fluid. In addition, infectious virus was confirmed on lesional skin and mucosal swabs. The observed virological kinetics together with the suspected pre-symptomatic transmission may lead to effective and sustained human-to-human transmission, particularly in sexual networks. Preventive measures such as vaccination and post-exposure prophylaxis may become important for MPX control in vulnerable groups.