Officials with the Centres for Disease Control and Prevention are sounding the alarm over a diarrhoea-causing superbug. The CDC’s data shows a noticeable rise in extensively drug-resistant strains of Shigella bacteria over the past half-decade. Though these infections are typically not severe, antibiotics are needed to prevent and treat life-threatening cases, and the bacteria can pass on their resistance genes to other troublesome germs.
Shigella is one of the most common sources of diarrhoea in the world, with an estimated 450,000 infections in the United States annually. Most cases are “mild” but still leave you suffering from about a week’s worth of diarrhoea, fever, and cramps. Sometimes, the diarrhoea becomes bloody, a condition known as dysentery. More rarely, the infection can cause complications such as severe dehydration, seizures, kidney damage and sepsis (often because the bacteria enter the bloodstream). Severe illness is more likely in the very young as well as people with weakened immune systems.
The bacteria rarely kills people in the U.S., though it’s still thought to hospitalize thousands every year. And it remains a major global health threat, especially in poorer areas of the world with inadequate healthcare and sanitation. According to the World Health Organisation, Shigella kills around 200,000 people a year. Most cases resolve on their own, with the typical treatment only being fluids and rest. But when these infections become more serious or happen in people at higher risk for serious illness, antibiotics are used to shorten its length. Unfortunately, Shigella is one of the many bacterial diseases that are steadily gaining resistance to these once-reliable weapons.
Shigella bacteria in general have learned to resist many antibiotics previously used as frontline treatments. But some strains are considered extensively drug-resistant, meaning they show resistance to every drug commonly used to treat them. In 2015, virtually 0% of Shigella cases in the U.S. carried these strains, according to the CDC’s national surveillance system. But in a health advisory released over the weekend, the agency reported that 5% of cases in 2022 were extensively drug-resistant.
It’s likely that many of these infections resolved on their own, and that they would still respond to lesser used antibiotics, either alone or in combination with others. But there’s no clear treatment strategy for these hardy strains, meaning that doctors would waste valuable time and resources trying to devise one. And in some severe cases, that delay could very well be fatal. If that isn’t bad enough, many of the genes that grant protection to these strains can be passed onto other bacteria in the gut, which will only further drive antibiotic resistance in general.
Another concern is that Shigella is incredibly contagious, so outbreaks can quickly get out of control. The bacteria can spread through contaminated food and water as well as person-to-person contact, including sex. Earlier this month, for instance, European health officials reported an widespread outbreak that has sickened hundreds of tourists (including a few from the U.S.) who stayed at five-star hotels in the island country of Cape Verde. Some of these cases are also thought to carry multidrug-resistant strains.
“Given these potentially serious public health concerns, CDC asks healthcare professionals to be vigilant about suspecting and reporting cases of [extensively drug-resistant] Shigella infection to their local or state health department and educating patients and communities at increased risk about prevention and transmission,” the CDC wrote in its advisory.
Researchers are actively working on Shigella vaccines and even testing them out in clinical trials, which should help stem the harm it causes. But in the meantime, people can reduce their risk of contracting or transmitting Shigella and many other stomach bugs by regularly washing their hands and carefully throwing out their children’s diapers. People who suspect they’re sick should stay home. They should also avoid swimming or preparing food for others while they have diarrhoea, and because it can spread through sex, they should wait at least two weeks after their symptoms clear up to have it again.