Sexually Transmitted Diarrhea Surges, Evolves into Drug-Resistant Superbug

Shigella bacteria, a common cause of dysentery, are infecting nearly half a million people annually in the U.S., leading to symptoms such as bloody diarrhea, stomach pain, fever, and vomiting. While historically associated with poor sanitation and daycare outbreaks, the infection is now increasingly spreading through sexual contact, particularly among gay and bisexual men, and evolving into drug-resistant strains. Experts describe this evolution as making the disease "close to untreatable."

Shifting Transmission Patterns

The bacteria typically spread through contaminated food or water, or by fecal-oral transmission due to poor hand hygiene. Children under five, travelers to areas with lower sanitation standards, and individuals experiencing homelessness are at higher risk. However, a July study indicated that the spread of Shigella through sexual contact grew 15% faster year-over-year between 2015 and 2020 compared to other transmission routes.

Emerging evidence suggests that sexual contact may now be the primary mode of transmission for Shigella. "Many men who have sex with men are unaware of the serious and increasing risk posed by sexually transmitted Shigella," said Cambridge geneticist Kate Baker, a lead author on the study, highlighting a potential lack of awareness fueling the infections. The study found that Shigella is considered "endemic" within these communities, meaning it is constantly and regularly present.

Rise of Drug Resistance

Concurrent with the shift in transmission, Shigella is demonstrating a growing resistance to antibiotics. The Centers for Disease Control and Prevention (CDC) reported that drug-resistant strains of the infection increased from 0% in 2011 to 8.5% in 2023. Baker noted that the disease has transitioned from being relatively treatable with common antibiotics to becoming nearly untreatable over the past decade.

This resistance may be partly due to "bystander resistance," where the use of incorrect antibiotics inadvertently allows the pathogen to develop resistance. The CDC data indicates that most drug-resistant Shigella cases have affected adult men. Research shows that individuals who contracted Shigella through sexual contact were hospitalized for an average of four to five days, often requiring different treatment protocols than those infected through other means.

Prevention and Treatment

Many Shigella infections resolve on their own within a week with rest and fluids. However, antibiotics are sometimes prescribed for severe cases to shorten illness duration and reduce contagiousness. The increasing antibiotic resistance complicates treatment.

The CDC recommends several prevention strategies, including thorough hand, genital, and anal washing with soap and water before and after sexual activity, cleaning sex toys, and using barrier methods such as condoms and dental dams. The California Department of Public Health also advises avoiding sexual contact with individuals who have experienced diarrhea within the preceding two weeks.