The CDC and local agencies have partnered to combat the outbreak, but it’s not under control yet.
The Centers for Disease Control and Prevention (CDC) is partnering with local agencies on a multipronged effort to eliminate an outbreak of Hepatitis A virus infection in San Diego county, California.
Success hinges upon decreasing the population that’s susceptible to infection, according to Monique Foster, MD, MPH, of the CDC’s Division of Viral Hepatitis.
“That’s best done through vaccination,” Foster said at a press conference held at IDWeek 2017 in San Diego, CA. “We also want to mitigate risk exposure through good hand hygiene and access to clean facilities.”
Disease rates declined with the introduction of the first Hepatitis A vaccine in 1996, but outbreaks can still occur, typically in high-risk populations like travelers, men having sex with men (MSM) and people who use illicit drugs, both intravenously and otherwise. Outbreaks can be extremely difficult to track back to a single source because of the disease’s long incubation period.
“The average incubation is 28 days, but could be anywhere from 15-50 days,” Foster said. “Individuals affected today probably won’t show any symptoms for 4 weeks, making it hard for those individuals to recall everything they did during their risk exposure period.”
The outbreak was initially identified in early 2017, when county officials noticed an increase in Hepatitis A cases from the baseline.
“From November 2016 to February 2017, between 7-9 cases would have been expected, yet 19 cases were reported,” said Eric McDonald, MD, MPH (pictured), Deputy Public Health Officer, San Diego County. “The risk factors in these patients were also unusual. Most cases in San Diego had previously been correlated to international travel, but 13 of these 19 cases were illicit drug users and 10 if the 19 cases were homeless.”
Officials issued a health alert on March 10, 2017. Since that time, 481 confirmed Hepatitis A outbreak cases have occurred. 70% of patients required hospitalization, and 4% died from their infections. 8 infected individuals identified as MSM, which indicated that it is unlikely that sexual transmission among MSM is contributing to the local outbreak in San Diego.
33% were homeless and illicit drug users, 17% were homeless only, 12% were illicit drug users only, 26% were either, and 12% were unknown.
“It’s important to mention that in the group that were neither homeless nor illicit drug users, most could be traced back to one of those at-risk groups, because they shared restroom facilities or had a close and ongoing relationship with somebody who was homeless or an illicit drug user,” McDonald said.
No food, water or drug sources have been identified as contributing to the outbreak, he added.
The overall strategy for outbreak control has been to vaccinate those people at risk and to promote proper sanitation and hygenine, and educate for prevention. Most children in San Diego county are well-vaccinated, however, adults are probably under-immunized, according to McDonald.
“In our outbreak, 45% of the cases were illicit drug users, nearly 1 in 4 had chronic hepatitis B or C, and yet none of these people had been previously immunized, which is a major missed opportunity for prevention,” McDonald said.
McDonald and officials from San Diego county recommended vaccinating at-risk target groups, which included homeless populations, janitorial workers and food handlers.
For food handlers, “this was just a precaution to prevent any potential crossover to the general population,” McDonald said. “It’s important to say that if you’re not in a specific risk group, you’re at a very low risk in this outbreak and we are not recommending vaccination.”
Local officials ensured that clinics that care for the homeless had vaccines and were using them, and helped to conduct mass immunizations at homeless service providers. Because homeless individuals usually only present for treatment in emergency departments, EDs were stocked with vaccines, as were needle exchange programs, behavioral health clinics, and substance abuse treatment centers across the county.
Public health nurses were paried with homeless outreach workers to head out on so-called “foot teams” to visit various homeless encampments across the county.
“We brought the vaccine to them instead of waiting for them to come to the vaccines,” McDonald said.
As of September 30, 2017, more than 54,000 adult Hepatitis A vaccines have been given across San Diego County, and 5,200 hygiene kits have been issued.