Shigella Infection on the Rise

Infections caused by Shigella bacteria, which can lead to dysentery, are becoming increasingly prevalent today—no need to be a trailblazer on the Oregon Trail to catch this bug.

This infection, now primarily spreading through sexual contact, is evolving to a point where treatments are becoming less effective, according to experts.

Each year, close to half a million people in the U.S. are afflicted by Shigella, experiencing symptoms like diarrhea that may be bloody or contain mucus, stomach cramps, fever, and nausea.

Researchers are uncovering the reasons behind the rapid spread of this troubling illness and its growing resistance to traditional treatments.

Transmission Through Sexual Contact

Shigella isn’t just an uncomfortable digestive issue; it can escalate into life-threatening conditions due to severe dehydration and fluid loss, potentially leading to septic shock, neurological complications, and internal bleeding.

The bacteria typically spreads through contact with contaminated feces, often due to insufficient handwashing or consuming unclean food or water. Just a tiny amount—around ten bacteria—can lead to illness.

Children under five are particularly susceptible, often contracting the infection in daycare or schools from peers who are still learning about hygiene. Additionally, travelers visiting areas with poor sanitation and individuals experiencing homelessness are also at a higher risk.

However, the sharpest uptick in Shigella infections is being seen among gay and bisexual men, as well as other men who have sex with men (GBMSM). Experts indicate that the bacteria have become effectively “endemic” in these communities, meaning they are consistently present.

A study released in July revealed that the sexual transmission of Shigella has increased 15% annually from 2015 to 2020, outpacing other sources like food or water contamination and outbreaks in childcare settings.

Emerging data indicates that sexual contact may now be the primary transmission route, although this can be difficult to assess since it’s often not inquired about during medical visits.

Many may be unaware that Shigella can be transmitted through sexual activity, which could be contributing to the increase in infections.

“There’s a serious and escalating risk linked to sexually transmitted Shigella that many men who have sex with men are not aware of,” said Kate Baker, a geneticist at Cambridge and lead author of the study.

Rising Resistance to Treatment

As Shigella spreads, it’s also becoming increasingly difficult to treat. According to the CDC, the proportion of drug-resistant strains soared from 0% in 2011 to 8.5% in 2023.

“This disease has evolved from being somewhat manageable with common medications to nearing untreatability over the last decade,” Baker noted.

What’s driving this change? Some experts suspect “bystander resistance,” which occurs when an unsuitable antibiotic is used, not only failing to eliminate the infection but also allowing it to develop resistance.

Most drug-resistant cases of Shigella have affected adult men. The strains that spread sexually are particularly severe, with research indicating that those infected through sex face an average hospitalization of four to five days.

“This isn’t simply one type of sexually transmitted diarrhea;” Baker explained, “multiple variants are emerging rapidly, all developing resistance to our current treatment options. It’s highly probable that someone who contracts Shigella sexually will need a different treatment than someone infected through contaminated food or water.”

Treatment and Prevention Strategies

While many Shigella cases resolve within a week with proper rest and hydration, antibiotics might be necessary for more severe infections, both to hasten recovery and reduce transmission risk.

However, the increasing resistance is complicating treatment options, prompting the CDC to call for enhanced prevention strategies.

The recommendations include:

• Thoroughly washing hands, genitals, and anus with soap and water before and after sexual activity, applicable to everyone engaged in any form of sex.
• Cleaning sex toys with soap and water.
• Utilizing barriers like condoms and dental dams.

The California Department of Public Health suggests an additional straightforward guideline: “Avoid sexual contact with anyone who has experienced diarrhea in the last two weeks.”