First detection and autochthonous transmission of monkeypox virus clade Ib in the Netherlands, October to November, twenty twenty-five

RAPID COMMUNICATION First detection and autochthonous transmission of monkeypox virus clade Ib in the Netherlands, October to November, twenty twenty-five

In October-November twenty twenty-five, eight autochthonous cases of monkeypox clade Ib virus infection were reported in the Netherlands. All cases were men who have sex with men aged twenty-five to sixty-five; none required hospital admission or antiviral treatment. Phylogenetic analysis combined with contact tracing suggest multiple introductions or cryptic circulation with onwards transmission within the community. Highly related international sequences were identified dating back to August twenty twenty-five, indicating sustained global community transmission of clade Ib outside the African continent.

In October twenty twenty-five, the first case of autochthonous mpox caused by infection with monkeypox virus clade Ib was diagnosed in the Netherlands. Following this initial case, seven additional cases were diagnosed by late November. Here, we describe the clinical presentation, transmission dynamics, public health response and phylogenetic analysis.

Clinical presentation

In early October twenty twenty-five, a man who has sex with men living with HIV, aged thirty-five to forty years, presented with malaise, abdominal pain, rectal tenesmus and mucous anorectal discharge in the emergency department at a hospital in Amsterdam. Physical examination showed four to five small pustular peri-anal lesions, without other skin lesions. Based on the similarities to mpox clade Ilb clinical presentations in the Netherlands since twenty twenty-two, mpox infection was suspected. Rectal swabs were PCR-positive for MPXV clade Ib.

In the following six weeks, seven more clade Ib mpox cases were diagnosed in the Netherlands, and later confirmed with whole genome sequencing. The main clinical findings for all eight cases are summarised in the Table. No indication for a major difference in clinical presentation of clade Ib infections was noted compared to clade Ilb infections. None of the eight cases required hospitalisation or antiviral treatment. None of them had received a recent vaccination for mpox. Concomitant bacterial sexually transmitted infections were identified in three of eight cases (chlamydia, gonorrhoea, syphilis) and, in one case, a gastrointestinal infection (Campylobacter spp.).