California Works to Contain Deadly Hepatitis A Outbreaks

Marcia Frellick

October 06, 2017

SAN DIEGO — After an unusual spate of hepatitis A — centered in San Diego but spreading to other jurisdictions — California is working with the Centers for Disease Control and Prevention (CDC) to contain transmission.

As of Thursday, there have been 17 deaths in the San Diego area and 481 confirmed cases, mostly among the homeless and people who use illicit drugs. Of those, 70% have been hospitalized. A special news conference here at IDWeek 2017 was added after the start of the meeting.

An unusual increase in the number cases was first noticed in March, said Eric McDonald, MD, medical director of the epidemiology and immunization services branch of the San Diego County Department of Public Health.

From November 2016 to February 2017, when it would be typical to see seven to nine cases, there were 19, he reported. The outbreak has reached a plateau now, at about 20 cases a week.

After aggressive investigation, "no food, water, or drug sources have been identified that are contributing to the outbreak," he said.

Different Population, Different Strain

Transmission among the homeless population is a departure in California; typically, transmission involves international travelers, according to experts. The genotype is also different. In California, the strain is 1B, whereas in other outbreaks, 1A is typical.

Since the introduction of a vaccine for hepatitis A in 1996, there has been a drastic decline in the number of new cases seen in the United States, but outbreaks still occur, said Monique Foster, MD, from the Department of Viral Hepatitis at the CDC.

Ensuring that people in at-risk populations are immunized is the top priority. Vaccination rates for children in the San Diego area are high, so the focus is on adults. Physicians can help by recommending that their at-risk patients be vaccinated when they come in for visits, the experts pointed out.

"In our outbreak, 45% of the cases are illicit drug users, and nearly one in four had chronic hepatitis B or C yet had not been previously immunized," said Dr McDonald.

To help contain the disease — which usually follows the fecal–oral route of transmission — the vaccine has been made available in emergency departments, needle-exchange programs, behavioral health clinics, and substance-abuse treatment centers. And vaccines are now being offered to all people entering the jail system to protect both the inmates from infection inside and people in the community when the inmates are released.

The county has also developed "foot teams" — public health nurses paired with homeless outreach workers — that go into encampments and vaccinate those most at risk.

This particular outbreak is complicated because hepatitis A has an average incubation period of 28 days. People "infected today probably won't show any symptoms for another 4 weeks," Dr Foster pointed out. This makes it difficult to track everything a patient has done during the risk exposure period, she explained.

In addition, the outbreak in San Diego is the result of person-to-person transmission, so sources are hard to identify. And the homeless population is transient, has a high prevalence of mental health disease, and has a general distrust of government systems.

"It's not unusual for large person-to-person hepatitis A virus outbreaks to last for quite some time — usually 1 to 2 years," Dr Foster reported.

California May Be in it for the Long Haul

The risk for transmission in the general population is extremely low, she emphasized, so there are no recommendations for mass public vaccinations.

In addition to San Diego, Santa Cruz County has reported a significant outbreak — about 70 cases — of the same genotype in the same populations.

"The presumption is that the virus traveled from San Diego," said Matt Zahn, MD, medical director of epidemiology at the Orange County Department of Public Health.

Los Angeles County has also seen a small number of cases —10 at the time the county declared an outbreak in mid-September — according to its website.

The vaccine is preventive even after you've been exposed.

One lesson from the San Diego outbreak is that "the homeless are at a unique risk for hepatitis A," Dr Zahn told Medscape Medical News. "The vaccine we have is wonderful. Even one dose will protect you 90% of the time (two doses, 99% or 100% of the time) for 20 years, or maybe even a lifetime."

The need to reach "that population is really an important thing coming out of this," he explained.

The San Diego outbreak will likely change the categories of people that the Advisory Committee on Immunization Practices recommend should be vaccinated.

"People with illicit drug use have always been recommended but the homeless have not been. I think there's a very good chance that that recommendation will change," Dr Zahn said.

There is no treatment for hepatitis A, so the solution is to diagnose patients, determine chains of contact, and get exposed people vaccinated, Dr Zahn said.

"The vaccine is preventive even after you've been exposed," he added.

Dr Foster, Dr McDonald, and Dr Zahn have disclosed no relevant financial relationships.

IDWeek 2017. Presented October 5, 2017.

Follow Medscape on Twitter @Medscape and Marcia Frellick @mfrellick

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