The magnitude of the 2022 multi-country monkeypox virus outbreak has surpassed any preceding outbreak. It is unclear whether asymptomatic or otherwise undiagnosed infections are fuelling this epidemic. We aimed to assess whether undiagnosed infections occurred among men attending a Belgian sexual health clinic in May 2022. We retrospectively screened 224 samples collected for gonorrhoea and chlamydia testing using a monkeypox virus (MPXV) PCR assay, and identified MPXV DNA-positive samples from four men. At the time of sampling, one man had a painful rash, and three men had reported no symptoms. Upon clinical examination 21 to 37 days later, these three men were free of clinical signs and they reported not having experienced any symptoms. Serology confirmed MPXV exposure in all three men, and MPXV was cultured from two cases. These findings show that certain cases of monkeypox remain undiagnosed, and suggest that testing and quarantining of individuals reporting symptoms may not suffice to contain the outbreak.

2022 年多国猴痘病毒爆发的规模超过了以往任何一次爆发。目前尚不清楚无症状或未确诊的感染是否加剧了这一流行病。我们的目的是评估 2022 年 5 月到比利时性健康诊所就诊的男性中是否存在未确诊的感染。我们使用猴痘病毒 (MPXV) PCR 检测对收集的 224 份淋病和衣原体检测样本进行了回顾性筛查，并从 4 份样本中鉴定出了 MPXV DNA 阳性样本。男人。采样时，一名男子出现疼痛性皮疹，三名男子报告没有任何症状。 21 至 37 天后进行临床检查，这三名男子没有出现任何临床症状，并且他们报告没有出现任何症状。血清学证实所有三名男子均接触过 MPXV，并且从两例病例中培养出 MPXV。这些发现表明，某些猴痘病例仍未确诊，并表明对报告症状的个人进行检测和隔离可能不足以遏制疫情爆发。