Sexually transmitted diarrhea is exploding in the United States. And it is becoming more and more resistant to drugs: ScienceAlert

An intestinal pathogen that causes diarrhea and vomiting turns into a dangerous and difficult to treat sexually transmitted infection (STI).

In the United States, approximately 450,000 people contract shigellosis each year, which can lead to dysentery.

Historically, this highly contagious virus was spread primarily through contaminated food or water while traveling, as well as from young children at daycare.

But since around the beginning of the century, Shigella bacteria has also emerged as a sexually transmitted infection.

Shigella Infections can make anyone sick, but are now considered “endemic” in some gay, bisexual and other men who have sex with men (GBMSM) communities.

Many of the strains transmitted in these communities have become resistant to several antibiotics.

Some are now superbugs, on the verge of becoming incurable.

A recent analysis by the US CDC found that among nearly 17,000 people Shigella isolates, extremely drug resistant (XDR) versions increased from 2011 to 2023.

In 2011, isolates resistant to five commonly used antibiotics represented 0% of samples. In 2023, they represented 8.5 percent.

The vast majority of these drug-resistant versions had infected adult men, many of whom had not traveled abroad in recent months.

Molecular biologist Shangxin Yang says hospital staff at the University of California, Los Angeles (UCLA) are currently seeing about one case of extremely drug-resistant disease. Shigella a month.

In 2022, by comparison, they only saw one case all year.

“It’s almost like an explosion of this pathogen in the community,” Yang told CIDRAP News at the University of Minnesota.

Sexually transmitted shigellosis was first reported in 1974, but it accounted for only a minority of cases at the time.

Now, new evidence suggests that sexual contact is a major route of transmission.

However, it is difficult to verify this information because patients and clinicians do not always realize that Shigella can be transmitted sexually and sexual history may not be recorded.

That said, according to US CDC data, more than a third of patients with extensively drug-resistant shigellosis were hospitalized, and almost half of those with known HIV status were HIV positive.

“Overall, this is a very concerning pattern of XDR Shigella strains seen among vulnerable populations,” CDC epidemiologist Naeemah Logan told CIDRAP News.

“This is by no means unique to the United States, but it is very much part of a larger global pattern.”

Geneticist Kate Baker of the University of Cambridge, lead author of a recent study in Lancet infectious diseasesidentified a similar surge in the UK.

“Many men who have sex with men are unaware of the serious and growing risk posed by sexually transmitted diseases. Shigella” Baker said in a July press release.

“This disease has gone from relatively treatable with commercially available drugs to almost incurable over the past decade.”

In March, the UK Health Safety Agency (UKHSA) warned that although most cases of Shigella resolve without treatment, more severe cases require treatment, and “available options become limited.”

In 2025, 86 percent of Shigella Sonnei samples and 94 percent of Shigella flexneri samples tested by UKHSA researchers showed resistance to antibiotics.

These are the two strains most prevalent through sexual contact among GBMSM in England.

In previous research by Baker and others, up to a third of patients with sexually transmitted diseases Shigella were hospitalized for four to five days on average.

“It’s not just a form of sexually transmitted diarrhea,” says Baker.

“These are multiple, overlapping variants that are all quickly becoming resistant to the drugs we use to treat them. It’s highly likely that if you have contracted your Shigella through sex, you need different treatment than someone who contracted it while traveling.

No one knows why, but Baker’s 2026 study indicates that “bystander resistance” is one of the determining factors.

This means that an antibiotic intended for one pathogen may not be the right drug or dose for another pathogen present, creating resistance as a side effect.

In response to the recent study, Alicia Calvo-Villamañán, a researcher at the Gulbenkian Institute of Molecular Medicine in Lisbon, Portugal, pointed out an intriguing association.

“When UK national treatment guidelines stopped recommending the use of (azithromycin) to treat gonorrhea infections,” they wrote, “the emergence of azithromycin resistance in Shigella slowed down.”

This does not mean that one causes the other, but it does suggest that treatment of other STIs may be a risk factor for drug resistance. Shigella infections, which are not often screened for as STIs.

The California Department of Public Health says the best way to prevent Shigella Sexual infection involves not having sex with someone who has had diarrhea within the past two weeks.

Using barriers during oral and anal sex is also recommended, as is washing dishes before and after sex.

To minimize transmission, anyone suspected of having Shigella should get tested and seek treatment if necessary.

“Clinicians should ask dysentery patients about sexual transmission and advise accordingly,” Daniel Richardson, sexual health consultant at Sussex University Hospitals, said in July.

“They need to know that sexually transmitted diseases Shigella has more antimicrobial resistance than other forms of the disease, and patients may need to check for other sexually transmitted diseases.