Los Angeles Hepatitis A Outbreak Defies Traditional Patterns

Los Angeles County health officials have declared a community-wide hepatitis A outbreak following an alarming tripling of cases since 2023 and the detection of elevated virus levels in wastewater surveillance. The outbreak, which has already claimed seven lives, is showing unusual patterns that have perplexed experts, as recent infections are increasingly occurring in individuals without the traditional risk factors of homelessness, drug use, or international travel.

The county has confirmed 165 hepatitis A cases since 2024, with 29 new cases in just the first three months of 2025, according to NPR.

Shifting Outbreak Demographics Baffle Experts

What particularly concerns public health officials is the changing profile of those affected. While hepatitis A outbreaks typically concentrate among specific populations with known risk factors, this outbreak shows signs of broader community transmission affecting people with no obvious exposure routes.

“When the outbreak started, we were mostly seeing it in people who had those risk factors,” explained Dr. Sharon Balter, Director of Communicable Disease Control and Prevention for the L.A. County Department of Public Health. “We’re seeing less of that and more of it in places where we’re not entirely sure where people got the virus.”

Officials also note that infections are less geographically concentrated than in past outbreaks. Early cases clustered largely in downtown Los Angeles, but new infections are appearing across wider areas with no clear connection to known cases, suggesting unidentified transmission routes within the general community. The LAist has produced detailed coverage of these evolving outbreak patterns.

Wastewater Surveillance Reveals Hidden Spread

The county’s declaration of an outbreak was triggered in part by a relatively new monitoring tool: wastewater surveillance. Since 2023, public health officials have analyzed samples from the Hyperion and A.K. Warren wastewater treatment plants, which receive sewage from approximately 75% of L.A. County residents.

These analyses have detected elevated concentrations of hepatitis A virus that suggest substantially higher community infection rates than indicated by clinical case counts alone. The wastewater data revealed continued viral circulation even during periods when clinical cases appeared to decline, providing an early warning that the outbreak was not resolving as initially hoped.

“We definitely think that the outbreak is bigger than the numbers imply,” Dr. Balter told the Los Angeles Times, referring to the discrepancy between confirmed clinical cases and virus levels detected in wastewater. This suggests many infections may be occurring without being diagnosed or reported. The official L.A. County outbreak declaration is available through the Department of Public Health website.

Vaccination Gap Leaves Adults Vulnerable

Health officials believe one major factor in the outbreak may be a significant vaccination gap in the adult population. Universal hepatitis A vaccination for children was implemented in Los Angeles County in 1999, but no catch-up campaign was conducted for older individuals who had already passed childhood when the vaccine was introduced.

“This does mean that there’s a large cohort of adults who may not have been vaccinated because they were born afterwards,” Dr. Balter explained. “We didn’t do a catch-up vaccine, and then some people may not have received the vaccine when they were younger.”

This vaccination gap is particularly concerning because California does not require hepatitis A vaccination for school entry, unlike many other childhood immunizations. The result is a substantial population of susceptible adults who have neither vaccine-induced nor natural immunity to the virus. The Newsweek report provides further analysis of this vaccination gap’s impact on outbreak dynamics.

Seven Deaths Underscore Serious Health Threat

While most people recover from hepatitis A without lasting liver damage, the disease can be deadly for certain vulnerable groups. In this outbreak, seven individuals have died from hepatitis A complications, emphasizing the serious nature of the threat.

“You can die of hepatitis A. At least seven people have died of hepatitis A in this particular outbreak,” Dr. Balter emphasized in a public statement. The fatalities have primarily occurred among older adults and those with underlying liver conditions or weakened immune systems.

Symptoms of hepatitis A include fever, fatigue, nausea, loss of appetite, jaundice (yellowing of the skin or eyes), stomach pain, dark urine, and diarrhea. The virus typically causes acute illness lasting several weeks to months, though some patients experience prolonged or relapsing symptoms. ABC7 Los Angeles provides comprehensive information about symptom identification and when to seek medical care.

Public Vaccination Campaign Launched

In response to the outbreak, Los Angeles County health officials have launched an expanded vaccination campaign, making hepatitis A vaccines freely available to any resident who has not previously been vaccinated. Mobile vaccination units are being deployed to high-risk areas, including encampments and interim housing sites for people experiencing homelessness.

“The hepatitis A vaccine is safe, effective, and offers long-term protection,” stated Dr. Muntu Davis, Los Angeles County Health Officer. “Getting vaccinated is simple, and it’s one of the most important things you can do for your own health and the health of our entire community.”

Full protection requires two doses administered at least six months apart, though a single dose provides substantial protection for most individuals. The vaccine is available through healthcare providers, many pharmacies, and county public health clinics for those without insurance coverage. Additional information on vaccine access can be found through the Contagion Live medical news resource and the Pride LA community health coverage.