How San Diego Coped With an Outbreak of Hepatitis A Among the Homeless

Naveed Saleh, MD, MS


January 09, 2018

Hepatitis A Among the Homeless

San Diego was recently ground zero for the largest hepatitis A outbreak in modern history. The outbreak hit home during IDWeek 2017, which was held in San Diego in early October. At the conference, the Centers for Disease Control and Prevention (CDC) and local public health officials addressed the outbreak in a special press conference held on October 5, 2017. Speakers at the conference were Eric McDonald, MD, MPH, medical director of San Diego County's Epidemiology and Immunization Services Branch, and Monique Foster, MD, MPH, a medical epidemiologist at the CDC.

In March 2017, local public health officials noticed that there was a substantial increase in the number of hepatitis A cases in San Diego County. Between November 2016 and February 2017, there were expected to be only seven to nine cases of hepatitis A; however, 19 cases were reported. Moreover, the distribution of these cases suggested that homeless populations and illicit drug users were at highest risk. "The risk factors in these patients were unusual," said Dr McDonald. "Most cases in San Diego had previously been related to international travel, but 13 out of 19 cases [in the current outbreak] were illicit drug users, and 10 of 19 were homeless."

Homeless Populations at Risk

From the start, the hepatitis A outbreak in San Diego was different from other recent US outbreaks in that the virus was transmitted by means of person-to-person contact. "Despite exhaustive investigations, no food, water, or drug sources have been identified that are contributing to the outbreak," said Dr McDonald. "There have been some geographic clusters that correspond to areas of high concentrations of homeless in the county."

Hepatitis A is transmitted in a fecal-oral fashion. Typically, outbreaks occur secondary to ingestion of foods. For instance, the last big outbreak of hepatitis A in the United States occurred in 2003 in Beaver County, Pennsylvania. The outbreak was spread by green onions used as an ingredient in a Mexican restaurant. In the 2003 outbreak in Pennsylvania, 601 people were infected with the virus, 124 were hospitalized, and three died.[1] In comparison, as of December 2017, in San Diego County there have been 561 cases, 378 hospitalizations, and 20 deaths. Dr McDonald noted that the San Diego outbreak "is very unusual in the postvaccine era. Ours is the largest person-to-person outbreak, and the experience with person-to-person outbreaks is not very high. Thirty years ago, we had community outbreaks. In the postvaccination era, we don't normally get them."

According to Dr McDonald, public health officials were quick to realize that the San Diego homeless individuals were at highest risk. "We immediately recognized the homeless as a target group, and in March [2017] recommended that they be vaccinated. In May, we expanded the local recommendation to include those who work in a close or ongoing basis with either homeless or illicit drug users." Dr McDonald stressed that without other risk factors, "the general population is at very low risk in this outbreak, and we aren't recommending the vaccine to the general population." Groups at highest risk for hepatitis A infection who should receive vaccination include men who have sex with men, illicit drug users (both injection and noninjection), people with chronic liver disease, and international travelers.

On a related note, it may seem like the San Diego outbreak, which was first recognized in March 2017, has lasted a long time. But according to Dr Foster, "It's not unusual for large person-to-person hepatitis A virus outbreaks to last for some time—usually over a year or between 1-2 years."

Strategies to Combat the Hepatitis A Outbreak

Ever since the start of the hepatitis A outbreak, public health officials in San Diego have been working tirelessly to vaccinate the homeless and those at risk. By September 30, 2017, with the assistance of community healthcare providers, the county had vaccinated 54,000 people. Of these, 36,000 vaccinations were given in clinical settings and 12,000 were given at field events. San Diego County health officials went so far as to enter homeless encampments to vaccinate those at risk.

Health officials from San Diego were vigilant in their efforts to engage, educate, and vaccinate the community. "The overall strategy for outbreak control," said Dr McDonald, "has been to vaccinate those people at risk, to promote proper sanitation and hygiene, and to educate for prevention." To this end, officials employed a novel combination of strategies including the following:

  • Distributing hygiene kits;

  • Setting up hand-washing stations;

  • Running a public advertisement campaign;

  • Setting up a phone hotline; and

  • Holding community talks.


One takeaway from the San Diego hepatitis A outbreak is the renewed importance of vaccinating at-risk groups—especially elderly patients with chronic liver disease who are at greatest risk for death from hepatitis A infection. Currently, coverage rates for hepatitis A and other vaccines are low.[2] "Despite hepatitis A being a vaccine-preventable disease," said Dr Foster, "the changing epidemiology reveals increased susceptibility of infection in older persons who are more likely to have underlying chronic issues, and that's important because it's more likely to burden the medical health systems in these cases."

The second—and most noteworthy—takeaway from the San Diego hepatitis A outbreak is the elucidation of the homeless as a distinct risk factor for infection with the disease. "The biggest new piece of the puzzle in this hepatitis A outbreak is the homeless factor.... Being homeless in and of itself was not seen as a risk of being infected with hepatitis A, but these other issues that may come with homelessness [such as chronic liver disease and illicit substance use] were. I think that the individuals who look at the data from this outbreak and other clusters among homeless will look to see if maybe homeless should be added to this at-risk group as far recommendations overall and not just in California," stated Dr Foster.

Finally, it's important to mention that even if the homeless are recognized as a specific risk group warranting hepatitis A vaccination, it's difficult to engage this population—especially outside of an emergency department setting where these individuals often receive healthcare. According to Dr Foster, "You can imagine that there are challenges addressing the needs of the high-risk population in this particular outbreak because of higher incidences of mental health disease and other comorbidities and possible distrust of the government—all of that adds to an already challenging task."


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