Epidemiology and the public health response of monkeypox

Monkeypox is a zoonotic disease, ie it can be transmitted between animals and humans through direct or indirect contact. After the eradication of smallpox and the end of universal smallpox vaccination, monkeypox is currently the most common orthopox virus infection in humans.

Since May 2022, a developing outbreak of monkeypox cases has been reported by several countries around the world, mainly affecting young men who self-identify as having sex with men. Four quick notices published in Eurosurveillance today describe cases diagnosed in Italy, Portugal, the United Kingdom (UK) and Australia.

UK: One outbreak, three separate incidents

Vivancos et al. describe the epidemiology and public health response to a monkeypox outbreak in the UK with 86 confirmed cases of monkeypox virus infections between 7 and 25 May 2022.

The authors grouped the currently known cases into three separate incidents: an isolated laboratory-confirmed case after a trip to Nigeria, two confirmed cases of monkeypox from a separate household cluster, including one case where the infections had already cleared up clinically (no laboratory confirmation), and the third. incident, 82 laboratory confirmed cases of monkeypox unrelated to the other two incidents, nor did patients report travel to areas where monkeypox is endemic.

While it is still under investigation whether the cases in Incident 3 may have been infected outside the UK, sexual health histories have found links to on-site sex, private sex parties and the use of geospatial dating apps, both in the UK and abroad. In the group linked to the third incident, gender information was available for 79 cases, all males. Of these, a vast majority 66 identified as gay or bisexual or other men who have sex with men.

So far, no single factor or exposure linking the cases has been identified.

According to Vivanco et al. “the current outbreak signals a change in basic assumptions about the epidemiology of MPXV in Europe with profound implications for surveillance and control” and constitutes the first reported sustained transmission of MPXV in the UK with evidence of human transmission on human beings through close contact, including in sexual networks.

Possible previously undetected spread of monkeypox suspected in Portugal

Portugal confirmed the first-ever case of human monkeypox in the country on 17 May 2022, and Duque et al. describe the outbreak detection of 96 confirmed cases of monkeypox so far from the Lisbon region and the Tagus Valley. The onset of symptoms of the first cases in Portugal was reported as early as April 29, 2022.

Most patients were not part of identified chains of transmission, nor could it be associated with travel or contact with symptomatic individuals or animals. According to the authors, this suggests a possible previously undetected spread of monkey pox.

Among the 23 confirmed cases described by Duque et al., 14 were HIV positive and the most common symptoms were exanthema (n = 14), inguinal lymphadenopathy (n = 14), fever (n = 13), genital ulcers (n = 6 ). The authors hypothesize “that MPX is circulating under the detection of the surveillance systems. While some cases have a clear epidemiological link, the lack of identified exposure raises unanswered questions in others.”

Samples of seminal fluid in Italy positive for monekypox

Vita et al. provide the clinical description of the four cases of monkeypox reported in Italy, in adult males with different clinical pictures from the existing literature, as the skin lesions were asynchronous, ranging from a single or clustered spot to an umbilical cord with progressive central ulceration and, finally, to scabs . Lesions were mostly localized to genital and perianal sites.

Biological samples of seminal fluid were positive for monkeypox viral DNA in all four patients, with a cycle of quantification ranging from 27 to 30. On this basis, the authors hypothesize that “although these findings cannot be considered definitive evidence of infectivity, they demonstrate viral shedding whose efficiency in terms of transmission cannot be excluded.”

Risk of bacterial superinfection

In their case description, Hammerschlag et al. share data on a virally suppressed HIV-positive patient who showed a genital rash in Australia in May 2022 after a visit to Europe, who was later hospitalized.

The clinical presentation was considered atypical in this case due to the presence of rash exclusively at the site of sexual contact 3 days before developing fever and due to the predominance of lesions in a central distribution with the fewest lesions present on the face and extremities distributed after the results.

The authors emphasize that “our patient’s hospitalization was not for severe manifestations of the Monkeypox viral infection, but to allow for diagnostic evaluation, pain management, and treatment of bacterial superinfection” and that the patient’s normal CD4+ infection T-cell counting and suppressing HIV viral load on antiretroviral therapy “were potentially important factors in preventing more serious consequences of his monkeypox infection”.