Objectives Outbreaks of shigellosis among men who have sex with men (MSM) have been reported since the late 1990s. HIV infection is an important risk factor. Since 2014, the global shigellosis epidemic has intensified. Whether chemsex (the use of crystal methamphetamine, γ-hydroxybutyrate or mephedrone to enhance sex) is a new risk factor has not been previously examined.
Methods We conducted a population-based, case–control study in Taiwan. Acute shigellosis cases diagnosed during the 2015 outbreak among MSM living with HIV were compared with those without shigellosis. CD4+ counts, plasma viral load (pVL), gonorrhoea, syphilis and amoebiasis records were obtained from the Notifiable Disease Surveillance System database. We invited cases/controls to provide information on illicit drug use and sexual behaviours, using a structured questionnaire.
Results Seventy-five shigellosis cases were compared with 225 controls. High pVL (>100 000 copies/mL; adjusted OR (aOR): 4.9, 95% CI 1.4 to 16.9), gonorrhoea (aOR: 29.4, 95% CI 2.3 to 340.2) and syphilis (aOR: 4.3, 95% CI 1.6 to 11.6) were independent risk factors of shigellosis. Twenty shigellosis cases and 59 controls completed the questionnaire. Oral-to-anal sex (aOR: 15.5, 95% CI 3.6 to 66.7), chemsex (aOR: 5.6, 95% CI 1.4 to 22.7) and poppers use (aOR: 10.9, 95% CI 1.9 to 64.2) within 12 months were independent behavioural risk factors of shigellosis.
Conclusions Chemsex is a new risk factor for shigellosis among MSM living with HIV, as identified in the 2015–2016 outbreak. Additional risk factors include poppers use, sexual risk behaviours and high pVL. Further studies on chemsex among MSM, which is a rising public health concern, are urgently required.
- bacillary dysentery
- sodium oxybate
- amyl nitrite
- sexual behaviour
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H-HW and Y-TS contributed equally.
C-TF and Y-CL contributed equally.
Handling editor Joseph D Tucker
Contributors C-TF and Y-CL conceived and designed the study. H-HW conducted the matched case–control analyses on the roles of CD4, pVL, past gonorrhoea, syphilis and amoebic infections. Y-TS enrolled the cases and controls through telephone interview, obtained information on illicit drug use and sexual behaviours, and conducted the unmatched case–control analyses on the roles of chemsex, poppers use and oral-to-anal sex. C-SC conducted laboratory confirmation of Shigella isolates, species identification and performed antimicrobial susceptibility testing. H-HW wrote the first manuscript. C-TF wrote the revised manuscript. H-HW, Y-CL, C-SC and Y-TS read and approved the final submitted version.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Ethics approval The study procedures were approved by the Institutional Review Board of Taiwan Centers For Disease Control (TCDC: registration numbers 1-04 301 and 105 303).
Provenance and peer review Not commissioned; externally peer reviewed.
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