Shigella, a bacterial infection that causes dysentery, is increasingly spreading through sexual contact, while some strains are becoming harder to treat due to rising antibiotic resistance.
The infection affects nearly 500,000 people in the United States every year and can cause bloody or mucus-filled diarrhea, stomach pain, cramps, fever and vomiting. Severe cases can lead to dehydration, bacterial and septic shock, neurological complications, internal bleeding and other serious infections.
Shigella usually spreads when infected fecal matter enters the mouth through contaminated hands, food or water. Experts say as few as 10 bacteria can be enough to cause an infection.
Children under five remain among those most likely to become infected, while travelers to areas with poor sanitation and people experiencing homelessness are also at higher risk. However, one of the fastest-rising groups is gay and bisexual men and other men who have sex with men.
A July study found that sexual transmission of Shigella increased 15 percent faster year over year between 2015 and 2020 than transmission linked to travel, food or nursery outbreaks. Experts also believe sex may now be a major route of transmission, although it is not always discussed when patients seek medical care.
Cambridge geneticist Kate Baker, a lead author of the study, said many men who have sex with men are unaware of the growing risk.
The CDC reports that drug-resistant Shigella strains rose from zero percent in 2011 to 8.5 percent in 2023, with most drug-resistant cases occurring among adult men.
Baker warned that Shigella has gone from being relatively treatable with standard drugs to “close to untreatable” over the past decade.
Many infections clear within a week with rest and fluids, but severe cases may require antibiotics. Increasing resistance is making treatment more difficult and has prompted calls for stronger prevention strategies.
