A recently published Chicago Department of Public Health (CDPH) -led study of people with mpox in the 2022-23 outbreak found a high rate of coinfections with sexually transmitted infections (STIs) including gonorrhea, chlamydia, syphilis, and HIV.

Epidemiologists from the Syndemic Infectious Disease Bureau analyzed surveillance and mpox case investigation data reported to the Chicago Department of Public Health (CDPH) between June 1, 2022, and March 9, 2023 and examined STI s and HIV diagnoses among people with confirmed and probable mpox.

The analysis, published as a Correspondence in The Lancet Infectious Diseases on Aug. 4, 2023 found that among mpox cases, co-infections with STIs were common; specifically, having a rectal site of gonorrhea infection was associated with a 7% increase in having an HIV and mpox coinfection as compared to genito-urinary site of infection and similarly, having a rectal site of chlamydia infection was associated with a 29% increase in having an HIV and mpox coinfection as compared to genito-urinary site of infection. In addition, those with a positive syphilis serology had a 55% increase of having an HIV and mpox coinfection.

Data showed that racial minorities also had increased rates of HIV and mpox coinfection as compared to White, non-Latinx persons, with those identifying as Latinx having a 34% increase in HIV coinfection, Asian, non-Latinx having a 90% increase in HIV coinfection, and Black, non-Latinx having over a 2-fold increase in HIV coinfection. Having information such as this may help guide efforts in prioritizing these populations in HIV, mpox, and STI prevention efforts.

These findings highlight the importance of rectal screening for gonorrhea and chlamydia among people with confirmed and probable mpox. Published data showed that previous history or concurrent co-infections with STIs are also important indicators to consider for HIV.

“The analysis also highlights our ability to leverage surveillance and case management data as opposed to relying on incomplete behavioral characteristics, which may not necessarily be an accurate proxy for risk, to identify vulnerable populations and use STI screening visits to prioritize prevention for the syndemic infectious diseases by administering mpox vaccination and/or providing pre-exposure prophylaxis (PrEP),” said CDPH epidemiologist Kara Herrera, PhD(c), MPH.

“Since there are high rates of HIV coinfection among individuals who had a rectal STI, at the time of mpox diagnoses we strongly encourage HIV-negative individuals to get on PreP for HIV and encourage health care providers to utilize the syndemic approaches by offering testing and prevention STIs, HIV and infections such as mpox,” Herrera said.

This analysis is also the first to characterize an association between positive syphilis serology and HIV co-infection among people with mpox and warrants further investigation, the CDPH team says.