Hepatitis A Outbreak Triples in Los Angeles as Wastewater Surveillance Reveals Wider Spread

Los Angeles County health officials have declared a community-wide hepatitis A outbreak following a dramatic surge in cases that has already claimed seven lives, with wastewater surveillance data indicating the virus is circulating more widely than individual case counts suggest, prompting calls for widespread vaccination among adults who may lack immunity.

The Los Angeles County Department of Public Health confirmed 165 hepatitis A cases since 2024, more than triple the number reported in 2023, with 29 cases already confirmed in the first three months of 2025—a concerning acceleration compared to the 14 cases reported during the same period last year.

Wastewater Data Reveals Greater Community Spread

Public health officials made the outbreak declaration after elevated levels of the hepatitis A virus were detected in county wastewater systems, indicating transmission extends beyond diagnosed cases. “In the first three months of 2025, we’ve had 29 cases of Hep A. This compares to 14 cases in the first three months of 2024,” explained Dr. Sharon Balter, Director of Communicable Disease Control and Prevention for the L.A. County Department of Public Health, as reported by ABC7 Los Angeles.

The county began monitoring wastewater for hepatitis A in September 2023, collecting samples from two major treatment plants that process sewage from approximately 75% of L.A. County residents. This surveillance method has become an increasingly valuable tool for detecting community-wide disease spread since the COVID-19 pandemic.

“While the data from wastewater isn’t a specific count of cases, it gives us a broad picture of virus circulation in the community,” explained Dr. Muntu Davis, Los Angeles County Health Officer, in the official public health announcement. “The sustained increase in wastewater concentrations, combined with the rise in clinical cases, meets our criteria for declaring an outbreak.”

Unusual Pattern of Infection

What particularly concerns health officials is the shifting demographic pattern of the current outbreak. While hepatitis A has historically affected primarily unhoused individuals and those who travel internationally, the majority of recent cases have been identified in people without these traditional risk factors.

“Of the 29 hepatitis A cases confirmed to date in 2025, most have been among people without travel or housing risk factors,” states the Los Angeles County Department of Public Health’s official release. This increase in infections among people without typical risk factors has corresponded with the elevated hepatitis A concentrations detected in wastewater.

“Typically, hepatitis A outbreaks occur among people who are unhoused, are consistent drug users, or have recently traveled to a country where hepatitis A is present. However, the data doesn’t reflect those populations this time,” reports LAist, highlighting the unusual nature of the current situation.

Vaccine Gap Identified

Health officials believe the outbreak may be partly due to an immunity gap in the adult population. The hepatitis A vaccine was introduced into the childhood vaccination schedule in Los Angeles County in 1999, but many adults born before that time never received the protection.

“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.”

The vaccine, which consists of two doses administered at least six months apart, provides long-lasting protection against the virus. Officials emphasize that even adults unsure of their vaccination status can safely receive the vaccine again.

Seven Deaths Highlight Severity

“You can die of hepatitis A. At least seven people have died of hepatitis A in this particular outbreak,” warned Dr. Balter in her ABC7 interview, underscoring the potential severity of the disease despite its relatively low mortality rate.

While most people recover from hepatitis A without lasting liver damage, it can cause severe illness in some individuals, particularly those with underlying liver conditions or weakened immune systems. In rare cases, it can lead to liver failure and death.

The current death toll represents a significant increase in mortality compared to typical hepatitis A outbreaks, raising concerns about whether a more virulent strain may be circulating or if the virus is reaching more vulnerable populations.

Transmission and Symptoms

Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus, which spreads primarily through the fecal-oral route. People can contract the virus by consuming contaminated food or water, or through close contact with an infected person.

The disease has a long incubation period of approximately seven weeks, which complicates outbreak investigations. Many infected individuals may not develop symptoms or seek medical care, further contributing to undetected community spread.

When symptoms do occur, they can include fever, fatigue, stomach pain, nausea, jaundice (yellowing of the skin or eyes), and dark urine. The CDC notes that while children under six often have no symptoms, older children and adults typically experience more severe illness lasting up to two months.

Public Health Response

County health officials have implemented a comprehensive response to contain the outbreak, including intensified surveillance, targeted vaccination campaigns, and public education efforts. Mobile vaccine units are offering free hepatitis A vaccines to homeless individuals at encampments and interim housing sites.

“The hepatitis A vaccine is safe, effective, and offers long-term protection. 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,” emphasized Dr. Davis in the public health announcement.

The county is also working closely with healthcare providers to increase awareness about the outbreak and ensure proper testing and treatment protocols are followed. Environmental health inspections have been increased at shelters and other facilities serving vulnerable populations.

Universal Vaccination Recommended

In light of the unusual pattern of transmission, health officials are now recommending vaccination for a much broader segment of the population than in previous outbreaks.

“We’re currently recommending that anyone who wants to be protected against hepatitis A should go ahead and get vaccinated,” stated Dr. Balter. “Full protection requires two doses of hepatitis A administered at least six months apart.”

Residents with insurance can receive the vaccine through healthcare providers and participating pharmacies, while those without insurance can access free vaccines through the county’s public health clinics.

Enhanced Surveillance Continues

The Los Angeles County Department of Public Health will continue to monitor both clinical cases and wastewater surveillance data to track the outbreak’s progression and evaluate the effectiveness of intervention measures.

The department has created a specialized outbreak investigation team that includes epidemiologists, environmental health specialists, and community outreach workers. This team is working to identify potential sources of infection and implement targeted control measures.

Health officials emphasize that in addition to vaccination, proper handwashing—particularly before eating or preparing food and after using the bathroom—remains essential for preventing the spread of hepatitis A and other infectious diseases.