Multnomah County health officials say they are tracking an increase in cases of drug-resistant Shigella this winter, but say the general public doesn’t need to take special precautions.
There have been 45 cases of Shigella reported in the Tri-County area, including Multnomah, Washington and Clackamas, in December so far.
Not all of those cases are related to each other, however; there are multiple distinct strains of the bacteria circulating. Since 2015, Shigella has caused multiple outbreaks among people who are homeless and other high-risk groups in the Portland area.
Shigella is a bacteria that causes inflammatory diarrhea. It’s transmitted when a tiny amount of poop gets into a person’s mouth. Common ways to get infected are changing diapers, caring for a sick person, intimate contact like sex, and swallowing contaminated water.
In Multnomah County, the largest cluster of current cases includes people who are homeless. Sexual contact appears to be the most common way the infection has been transmitted, indicated in about half of the cases.
The county says the most effective intervention it has to contain the spread is providing motel vouchers for people sick with Shigella.
“It gets them off the streets at the time when they are potentially most infectious, so they aren’t visiting shelters or potentially spreading it to other people. It also gives them ready access to hygiene and toileting so they can take care of themselves,” said Sara McCall, communicable disease program manager with the county.
Cluster not localized in Portland’s Old Town, county says
County health officials say the risk to the general public is low. Shigella infections are closely monitored by the Centers for Disease Control and Prevention, so county public health workers interview each person confirmed to have been infected. To date, the county hasn’t seen any unexplained transmission that would indicate a broader outbreak.
“We have good explanation for the folks who do acquire infection,” said Teresa Everson, interim Multnomah County health officer. “The transmission we’re seeing makes sense, for how we know Shigella spreads.”
Everson also clarified that the case cluster is not localized in Portland’s Old Town neighborhood. Recent news reports and a social media post from the Portland Police Bureau have described the outbreak as impacting Old Town.
“There is no clear geographic pattern to our cases at this time. It’s something we track really closely, but there’s no specific area for us to focus interventions on,” she said.
The infection is endemic in most countries and relatively common in the global south, where it causes hundreds of thousands of deaths, particularly among children.
Related: What is Shigella, the increasingly drug-resistant bacteria the CDC is warning about?
Emergence of drug-resistant Shigella strains
Earlier this year, the CDC reported an increase in antimicrobial-resistant strains of Shigella among adults in the United States, particularly men who have sex with men, people living with HIV, people who are homeless, and international travelers.
The agency stressed the importance of prevention and reducing transmission.
Nationally, about 5% of Shigella cases reported in 2022 were resistant to all five commonly recommended antibiotics.
While most Shigella infections don’t require treatment, the emergence of extremely drug-resistant strains is making it harder to treat the most serious cases.
And drug-resistant Shigella strains could spread their resistant genes to other bacteria found in the human digestive tract.
Multnomah County first alerted health care providers of the local cluster in November, encouraging doctors to consider a Shigella diagnosis for patients with symptoms, especially among groups considered at higher risk.
There are two Shigella strains currently circulating in the county, each with a different pattern of antibiotic resistance. Both strains are resistant to four of the five common antibiotics — but not the same four. The result, according to the county health department, is that many patients receive antibiotics which are ineffective, prolonging illness and allowing for additional spread of the bacteria.
Everson said if people are concerned about their own exposure, the best protection is washing their hands thoroughly after any exposure to poop and before meals.
Correction: The story has been updated to state that 45 cases of Shigella have been recorded in the Tri-County area, including Multnomah, Washington and Clackamas, in December so far.