You may have heard about an intestinal infection affecting men who have sex with men (MSM) in Portland. It’s called shigella, a bacterial infection that causes symptoms that resemble food poisoning—diarrhea, fever, nausea, vomiting, cramps, and sometimes more serious issues.

The recent cases affecting gay and bisexual men in the area have come from sexual contact. More commonly, though, shigella is spread between children or through contaminated water, or comes from contaminated food, such as the outbreak this fall that recently infected over a hundred people who ate at the same restaurant in San Jose, California. Fortunately, it’s treatable using antibiotics.

The most obvious way the shigella bacterium is transmitted sexually is through oral-anal contact (rimming). But the bacteria can also travel to your mouth on your hands or on genitals after playing with an infected person’s anus. The Multnomah Health Department is recommending washing up thoroughly before and after sex to clean the bacteria off. If you think you might be sick, you can protect others by taking a break from sex until you see your doctor for a diagnosis.

There are cases of shigella that stay mild, and some people never even know they are infected. But having only minor symptoms doesn’t mean someone else won’t get a serious illness if you pass it to them. Infections can be especially risky for people whose immune systems are compromised by other health concerns, who have untreated HIV, or the elderly.

If you are infected with the shigella bacteria the condition is called shigellosis, with symptoms that start 1-6 days after being exposed. The illness usually lasts about a week after that but in more severe cases can take much longer. It can be contagious before there are any symptoms, as well as for a few weeks after the symptoms go away.

Shigella is less common in North America these days, but the disease has existed since before people even knew about the bacteria that cause it. Shigella is one of the bugs that can cause dysentery—diarrhea with blood in it—which used to kill people through dehydration before oral rehydration therapy was developed. Since then, clinicians use a simple treatment called oral rehydration therapy, which is water containing a specific ratio of salt and glucose (sugar), that enables sick intestines to absorb fluids and electrolytes. But diarrheal diseases like shigella are still very serious illness in the developing world where people might not have access to treatment.