Shigella outbreak extra rough on S.F.’s vulnerable homeless

An outbreak of shigellosis — a highly infectious gastrointestinal infection — that started in November and hit San Francisco’s homeless population especially hard has heightened awareness about how vulnerable to infection people living on the streets and in shelters may be, and resulted in new measures to prevent the spread of disease.

San Francisco has seen more than 200 cases of shigellosis — commonly called shigella, the name of the bacteria that cause the disease — since November. The actual numbers are probably much higher since many people who fall ill never get diagnosed. The city typically sees five to 10 cases a month.

Aside from the size of the outbreak, public health officials are concerned about the community most affected — more than a quarter of patients are homeless — and because the strain of bacteria involved appears to be resistant to the antibiotic most commonly used to treat shigella.

Because homeless people have been so hard hit, public health officials have targeted that group to halt the outbreak. Along the way, they’ve picked up some deceptively simple techniques for promoting infection control among homeless communities.

For example, public health officials have passed out small hand sanitizers to people living outdoors in homeless encampments who may not have access to clean running water. And they taught homeless outreach teams to do simple health evaluations and distribute oral rehydration packages to people suffering diarrhea, the main symptom of shigella.

“It was a very quick, natural process to say, 'Gee, we need people to have more access to hand-washing,’” said Dr. Barry Zevin, medical director of San Francisco’s Homeless Outreach Team. “Now that I look back on it, it seems obvious, like why weren’t we distributing hand sanitizer for a long time?”

Public health officials also visited places that distribute free meals to the homeless — including St. Anthony Dining Room and Glide Memorial Church — to look for possible gaps in infection control. City inspectors did not find any source of infection in the dining halls.

The outbreak appears to be winding down now, and public health officials said that may be in part because the new measures are working. The shigella outreach peaked in December with 102 cases, but has since fallen to 27 cases in February, the most recent month for which numbers are available.

The outbreak was a reminder that homeless communities can be especially vulnerable to infectious diseases, said Dr. Cora Hoover, director of communicable disease control and prevention for the San Francisco Department of Public Health.

“This was an outbreak of disease that could really be a crisis” without early and aggressive public health intervention, Hoover said. “And it really got us thinking about how do we respond to a crisis when it happens, because any kind of crisis is quite likely going to have an impact on homeless populations.”

Shigella is a common source of gastrointestinal illness, infecting about half a million people in the United States every year, and it’s most often associated with international travel. In fact, it’s sometimes referred to casually as traveler’s diarrhea.

The bacterium — similar to the more notorious norovirus — is easily spread by oral-fecal contact. Symptoms include diarrhea, fever and abdominal pain. Most people will recover in about a week with no treatment. But some people can become severely dehydrated and need medical care. Doctors may prescribe antibiotics for those cases to ease symptoms and speed up recovery. Shigella is rarely fatal.

The San Francisco outbreak is part of a national wave of the illness that was caused primarily by the drug-resistant strain of shigella. Last week, the U.S. Centers for Disease Control and Protection reported that 90 percent of cases tested nationwide were resistant to Ciprofloxacin, the main antibiotic used to treat shigella.

Losing the first-line drug therapy can make cases tougher and more expensive to treat. Plus the longer people remain ill, the longer they’re contagious and able to continue spreading disease.

The fact that so many cases were identified among homeless people was somewhat surprising, Zevin said — not because they don’t get sick, but because they frequently don’t have access to medical attention or aren’t tested and diagnosed with specific infections. Many of the homeless people diagnosed in this outbreak had become so ill that they were hospitalized, and therefore tested to improve treatment.

Part of the outbreak response was to talk to homeless people about the symptoms of shigella and encourage them to seek care if they felt ill. And if they couldn’t go to a health care clinic, or wouldn’t, outreach officials talked to them about how to care for and prevent dehydration, and how to protect themselves from future infection.

“Homeless people really care about their health. You’re not up against people who just don’t care,” Zevin said. “But there are many barriers to obtaining health care, many barriers to basic sanitation and public health measures. We need to be able to recognize what those barriers are and remove them as much as we can.”