Outbreak of infectious intestinal illness declared among Toronto's underhoused community

Shigella bacteria in an illustration made available by the Centers for Disease Control and Prevention. (CDC)

A highly contagious and drug-resistant bacterial illness has sickened several members of Toronto’s underhoused community, says the city’s health unit.

On Wednesday, Toronto Public Health (TPH) confirmed to CP24.com that it declared an outbreak of Shigellosis on Dec. 6.

Associate Medical Officer of Health Dr. Howard Shapiro said they are aware of nine cases of the intestinal disease among people experiencing or at risk of homelessness in the city.

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“The number of cases among this vulnerable population is higher than in previous years. However, the risk to the general public remains low,” he said in a statement provided to CP24.com.

A spokesperson for TPH said the current investigation shows the onset of symptoms for the first outbreak case occurred on or after Sept. 3, although it is not known where the individuals who contracted the illness were staying.

As of November 28, there have been a total of 101 cases of Shigellosis reported to TPH in 2024, compared to 119 in all of 2023.

The health unit, which first reported on the outbreak in its Dec. 9 e-newsletter for physicians, said that while the number of cases in the city as a whole is not unusual, it is out of character to see nine infections in the underhoused community. On average, there are one or two cases reported in this segment of Toronto’s population at any given time, TPH said.

Shapiro went on to say that public health is “engaging” Toronto Shelter & Support Services along with health care providers and social service agencies to “ensure that they are informed about the current situation and protocols to reduce the risk of transmission for clients and staff in these service settings.”

He said this includes ensuring that shelter staff continue to follow infection prevention and control measures already in place like continued use of personal protective equipment, enhanced cleaning, and symptom screening and monitoring.

The investigation is ongoing, Shapiro said. 

A man is silhouetted in a tent at a homeless encampment in Toronto on Sunday November 8, 2020. THE CANADIAN PRESS/Chris Young

Shigellosis occurs when a person is infected with a well-known bacterial pathogen called Shigella. It most often spreads through contact with fecal matter from an infected person or by eating food or drinking water contaminated with it.

Stools may continue to be infectious for up to 4 weeks, TPH noted.

The common symptoms of Shigellosis, which has a one- to three-day incubation period, are diarrhea, fever, nausea, vomiting, and abdominal cramps.

Shigellosis typically self-resolves within seven days, however its symptoms may become severe and could lead to hospitalization, said Dr. Stephen Hwang, a general internist and researcher with the MAP Centre for Urban Health Solutions at St. Michael’s Hospital.

Hwang, whose studies are primarily focused on the unhoused community, said what’s concerning about this bacterium is that it spreads easily.

“Shigella is known for being very easily transmissible, even with a tiny dose,” he told CP24 on Wednesday.

“Most infections require a fairly large dose to spread, but Shigella only needs 10 bacteria to cause an infection.”

Illness especially concerning for unhoused people, says doctor

Hwang said this is especially concerning for people experiencing homelessness, especially those staying in shelters where large numbers of people congregate and share washroom facilities.

“All it takes is for one person to have it, then it can spread through a whole facility,” he said.

Encampments are also ideal breeding grounds for Shigella, Hwang said, as those staying in them may be sharing portable washrooms and usually don’t have consistent access to proper sanitation.

“These are places where maintaining hand hygiene is very difficult,” he said, noting that he hasn’t seen or treated anyone with Shigella as of late.

“It’s unfortunate, but not surprising, that this illness is spreading among this community. … Homelessness creates circumstances that are ideal for the spread of infections like Shigella.”

Hwang added that people experiencing homelessness who contract Shigella may become sicker than those who have a home as they can rest and take in enough fluids to recover.

In some cases, antibiotics may be administered to infected persons who have a weakened immune system, TPH said, however several common antibiotics are highly resistant to certain strains of this bacteria, Hwang said.

“That’s something we have to take into account when treating patients,” he said.

Tips to prevent the spread of Shigellosis:

-Stay home and don’t prepare food, or share food, water, or other personal items (clothes, bedding, cigarettes, needles, or sex toys) with others who have Shigellosis or diarrhea

-Wash your hands often with soap and water, especially before eating or making food or after using the washroom

-Avoid sexual contact with others while sick and wait at least two weeks after diarrhea ends to resume sexual activity, and practice good hygiene before any sexual activity

-Avoid public swimming facilities while sick

(Courtesy TPH)