Monkeypox outbreak 2022 – an overview of all cases reported to the Cologne Health Department

Abstract Purpose: The international monkeypox outbreak in May 2022 marks the occurrence of another previously atypical infectious disease in Europe. This study’s objective was to present a comprehensive overview based on data gathered by the Health Department of the city of Cologne. Methods: In this retrospective observational study, 368 individuals reported to the Cologne Health Department as PCR-positive for monkeypox were included. Data were collected in structured telephone interviews and digitally processed. Results: The first monkeypox case in Cologne was recorded on May 24, 2022. The local outbreak lasted approximately 4 months and reached its peak in July. The last reported case in Cologne occurred on September 17. Transmissions mostly occurred through sexual contacts (67.4 %) or other close physical contacts (4.6 %) between men, but also through fomites, in the context of events or occasionally in the work environment. In 21.5 % of cases, no route of infection could be determined. The mean incubation period was 8.2 days. Clinically, monkeypox infections usually presented with skin and/or mucosal lesions accompanied by general symptoms. In 74.8 % of cases, a prodromal stage was absent. Initially, the rash often had an unspecific appearance, but in the further clinical course, it usually passed through the typical stages. Most infections resolved spontaneously under home care. In 3.5 % of cases, however, inpatient hospitalisation was required. Conclusions: Most transmissions occurred through sexual contact. Although the majority of infections in Cologne affected the MSM community, there were also cases outside this context. The observed average incubation period was shorter than initially assumed. Mucosal involvement and associated symptoms occur in a relevant number of cases and can lead to more severe clinical courses. In the case of an unclear rash or symptoms suggesting mucosal involvement, monkeypox should be considered as a differential diagnosis. The surveillance data collected in the health authorities provided important information for adapting the public health measures taken against the spread of monkeypox in the population.