Since March, Multnomah County health officials have braced for an outbreak of disease in homeless camps.

That outbreak is here, but rather than COVID-19, it's a severe version of diarrhea called shigellosis.

"We have now identified a clear increase in shigellosis," Dr. Jennifer Vines, the tricounty health officer, tells WW.

In a typical year, there might be 20 cases of shigellosis reported in the county. So far this year, there have been 74 cases reported. Of those, 27 cases are people who are "unhoused or unstably housed."

Shigellosis is a bacterial disease that Vines says spreads most aggressively through populations of men who have sex with men and drug users (mostly meth), and makes its way into homeless camps. The strain that showed up locally is resistant to antibiotics and can cause severe diarrhea for a week.

As of last week, just 46 people who were homeless or had been within the past six months have been diagnosed with COVID-19. The county has reported no large outbreaks at homeless camps or shelters other than the shigellosis outbreak.

In Oregon and other West Coast cities with large homeless populations, public health officials feared that COVID-19 would spread rapidly through camps because people live closely together in often unsanitary conditions and are often medically vulnerable.

To keep COVID-19 at bay, the Joint Office of Homeless Services has distributed more than 100,000 masks, 68,000 sanitizing wipes, and more than 3,000 liters of hand sanitizer. It has also distributed a couple of dozen portable toilets and hand-washing stations.

The shigellosis outbreak has placed heavy demands on those temporary public restrooms. "Sanitation is somewhat better but still inadequate," Vines says.

Coincidentally, county officials traced a shigellosis outbreak in August to a downtown food cart. That outbreak sickened a dozen people, but despite the fact it was the same drug-resistant strain of the shigella bacteria, Vines says officials believe it is unrelated to the outbreak in the camps.

Vines adds that the risk of shigellosis traveling outside the camps is low. It's usually the other way around, she says: Diseases spread from the housed population to the unhoused.

If there's good news for people living in homeless camps, it's that COVID-19 has brought them an unprecedented number of volunteers and outreach workers bringing hygiene kits, clean clothes, toilet paper and other necessities. The bad news: The weather will soon change and shigella travels via water. "Shigella spreads really easily," Vines says, "so it gets worse in the rainy season."

Correction: This story originally said there had been more reported cases of shigellosis than COVID-19 among people who are homeless. That is not the case. WW regrets the error.