Screening for monkeypox virus infections in men who have sex with men in a sexual health clinic in Hanoi, Viet Nam.

In early 2022, an increase in mpox (formerly known as monkeypox) cases occurred in countries without previous mpox infections; there are now more than 81 000 cases reported from 110 countries.1WHO2022 monkeypox outbreak: global trends.https://worldhealthorg.shinyapps.io/mpx_global/Date: 2022Date accessed: November 28, 2022Google Scholar Infections during the current outbreak are associated with sexual transmission and disproportionately affect gay, bisexual, and other men who have sex with men (GBMSM).1WHO2022 monkeypox outbreak: global trends.https://worldhealthorg.shinyapps.io/mpx_global/Date: 2022Date accessed: November 28, 2022Google Scholar Approximately half of reported mpox cases are people living with HIV infection, and a large proportion of people without HIV infection are taking HIV pre-exposure prophylaxis (PrEP).1WHO2022 monkeypox outbreak: global trends.https://worldhealthorg.shinyapps.io/mpx_global/Date: 2022Date accessed: November 28, 2022Google Scholar, 2Thornhill JP Barkati S Walmsley S et al.Monkeypox virus infection in humans across 16 countries—April–June 2022.N Engl J Med. 2022; 387: 679-691Crossref PubMed Scopus (295) Google Scholar, 3Curran KG Eberly K Russell OO et al.HIV and sexually transmitted infections among persons with monkeypox—eight US jurisdictions, May 17–July 22, 2022.MMWR Morb Mortal Wkly Rep. 2022; 71: 1141-1147Crossref PubMed Google Scholar Asymptomatic monkeypox virus infections have been reported. A retrospective study of rectal and oropharyngeal specimens collected from 224 men in a sexual health clinic in Belgium in May, 2022, reported a 1·3% prevalence of asymptomatic infections.4De Baetselier I Van Dijck C Kenyon C et al.Retrospective detection of asymptomatic monkeypox virus infections among male sexual health clinic attendees in Belgium.Nat Med. 2022; 28: 2288-2292Crossref PubMed Scopus (32) Google Scholar A retrospective study of rectal specimens among 706 men in a sexual health clinic in France found a 6·5% prevalence of asymptomatic infections.5Ferré VM Bachelard A Zaidi M et al.Detection of monkeypox virus in anorectal swabs from asymptomatic men who have sex with men in a sexually transmitted infection screening program in Paris, France.Ann Intern Med. 2022; 175: 1491-1492Crossref PubMed Scopus (22) Google Scholar There is uncertainty about the extent to which asymptomatic infections occur and contribute to monkeypox virus transmission. In September, 2022, there were no reported cases of mpox in Viet Nam and there was little diagnostic testing capacity. However, cases were reported in several nearby countries, leading to concern for under-detection of monkeypox virus infections in Viet Nam.1WHO2022 monkeypox outbreak: global trends.https://worldhealthorg.shinyapps.io/mpx_global/Date: 2022Date accessed: November 28, 2022Google Scholar The objective of the current study was to establish if undiagnosed and asymptomatic mpox infections occurred in GBMSM enrolled in an HIV PrEP programme in Hanoi, Viet Nam. The study used remnant rectal specimens, collected from July 1, 2022, to Aug 31, 2022, as part of an ongoing research study for the detection of multisite Chlamydia trachomatis and Neisseria gonorrhoeae infections. Rectal specimens were self-collected swabs placed in an Alinity m multi-collect tube (Abbott Molecular, Des Plaines, IL, USA). Specimens were stored at –20°C and were thawed before monkeypox virus testing. DNA extraction was done with DNeasy Blood and Tissue Kits (Qiagen, Germantown, MD, USA). The real-time PCR assay was done with monkeypox virus generic (G2R_G) primers and probes6Li Y Zhao H Wilkins K Hughes C Damon IK Real-time PCR assays for the specific detection of monkeypox virus West African and Congo Basin strain DNA.J Virol Methods. 2010; 169: 223-227Crossref PubMed Scopus (108) Google Scholar and LightCycler 480 Probes Master mix (Roche Diagnostics, Meylan, France) on an ABI 7500 Fast platform (Applied Biosystems, Foster City, CA, USA). Phocid herpes virus was used as an internal control for the extraction and amplification steps7Niesters HG Clinical virology in real time.J Clin Virol. 2002; 25: S3-12Crossref PubMed Google Scholar and synthetic monkeypox virus DNA was used as an external positive control. Specimens were considered positive if the cycle threshold value was 40 or more. Demographic and clinical information were collected from study participants. All study participants provided informed consent for additional analyses on stored specimens and the study was approved by the Institutional Review Board at Hanoi Medical University (HMUIRB580). In total, remnant rectal specimens from 152 participants were submitted for testing. All participants were male, reported having sex with male partners, and were taking HIV PrEP. The median age was 25·9 years (IQR 21·7–30·3). The median number of male sex partners in the previous month was 1 (IQR 1–3) and 15 (9·9%) of the 152 participants reported having group sex in the previous 6 months. In the previous 3 months, 12 (7·9%) of the 152 participants reported a diagnosis of a sexually transmitted infection. On the day of specimen collection, 53 (34·9%) of the 152 participants reported any sexually transmitted infection symptoms in the previous week and 24 (15·8%) reported rectal symptoms. Among the rectal specimens submitted for testing, 32 (21·1%) were positive for C trachomatis and 23 (15·1%) were positive for N gonorrhoeae. All the remnant rectal specimens submitted for testing were negative for monkeypox virus. Monkeypox virus was not detected in rectal specimens from 152 GBMSM enrolled in an HIV PrEP programme in Hanoi, Viet Nam from July 1, 2022, to Aug 31, 2022. During the study period, diagnostic testing for mpox in Viet Nam was not widely available and data on the prevalence and incidence of infections were not available. Subsequently, the first case of mpox in Viet Nam was reported on Oct 3, 2022, in a woman aged 35 years who was admitted to hospital on Sept 22, 2022, after returning from Dubai, United Arab Emirates.8Vietnam PlusVietnam announces first case of monkeypox.https://en.vietnamplus.vn/vietnam-announces-first-case-of-monkeypox/239428.vnpDate: 2022Date accessed: December 8, 2022Google Scholar Currently, there does not appear to be sustained monkeypox virus transmission within Viet Nam. Increased testing capacity for monkeypox virus infections is needed for surveillance and disease control. The need for testing is especially important in low-income and middle-income countries where access to testing is already low.9Chamas C Malheiros Barbeitas M Correa M Kameda K Dias De Oliveira AC Villarinho L Innovation in diagnostics: addressing gaps in low- and middle-income countries.Bull World Health Organ. 2022; 100: 467Crossref Scopus (0) Google Scholar Moreover, screening for asymptomatic infections in populations at increased risk for infections can allow for early case detection and a fast response to outbreaks.10Reda A Ehab El-Qushayri A Shah J Asymptomatic monkeypox infection: a call for greater control of infection and transmission.Lancet Microbe. 2022; 4: e15-e16Summary Full Text Full Text PDF Scopus (1) Google Scholar The deployment of a diagnostic test for mpox in Viet Nam and the use of retrospective specimens allowed for the rapid assessment of undetected transmission. Based on epidemiological data, our study population of sexually-active GBMSM was at increased susceptibility for monkeypox virus infections. Therefore, monkeypox virus infections not being detected during this time is an important finding. Integrating mpox testing into settings where populations at increased risk of infections seek care can aid in surveillance efforts. This work was supported by the National Institutes of Allergy and Infectious Diseases (R21AI157817 to JDK and GML), Fogarty International Center (K01TW012170 to PCA), and the Wellcome Trust (106680/B/14/Z). We thank Nguyen Thi Thu Hong (Emerging Infections group, Oxford University Clinical Research Unit, Ho Chi Minh City, Viet Nam) and Nguyen Cong Thanh (Hanoi Medical University, Hanoi, Viet Nam) for their logistical support. We declare no competing interests.