Viral hepatitis and syphilis remain important public health issues because of chronic forms and clinical complications. The omission of hard-to-reach and disadvantaged populations from public health and medical research is one of the current barriers to achieve the WHO target of reducing the burden of viral hepatitis and syphilis by 2030 [ 1 ]. Illegal gold miners in French Guiana, a French overseas territory in South America, are a perfect example of this type of population: they comprise about 10 000 people from Brazil living in a remote mining camp in the rainforest. We have previously shown that gold miners are a vulnerable population, notably with a human immunodeficiency virus (HIV) prevalence of 1.4% (95% CI 0.29–2.56) in a context where prostitution is frequent and condom access is difficult [ 2 ]. This study, nested in the Orpal study conducted in 2015 (NCT02903706) [ 3 ], aimed to estimate the prevalence of hepatitis B (HBV), D (HDV) and C (HCV) viruses, and syphilis in the specific population of illegal gold miners in French Guiana. The data collection method was previously reported [ 3 ]. Subjects provided informed consent. This ancillary study was approved by the Cayenne General Hospital Ethics committee.