32 Hepatitis A Outbreaks Linked to Drinking Water Identified From 1971-2017

Between 1971 and 2017, 32 waterborne outbreaks of hepatitis A were identified in the United States, according to an article published in the US Centers for Disease Control and Prevention’s (CDC) Morbidity and Mortality Weekly Report.

As part of an investigation, authors of the report assessed data from the Waterborne Disease and Outbreak Surveillance System collected between 1971 and 2017. Although drinking water-associated outbreaks are rarely reported in the United States, they were the most commonly reported etiology for outbreaks associated with untreated groundwater from 1971-2008.

Hepatitis A can persist in water and remain infectious for months and, according to the authors of the report, the 32 outbreaks resulted in 857 total cases, which were all documented prior to 2010.

Untreated groundwater was associated with 72% of the outbreaks, resulting in 68.3% of total cases in these outbreaks. The report indicates that 4 outbreaks that occurred between 1995-2009 were caused by contaminated drinking water in individual water systems, which are not required to meet national water standards.

No waterborne-associated outbreaks of hepatitis A were reported from 2010 to 2017. The investigators hypothesize that this decrease in cases could be a direct result of uptake of the hepatitis A vaccine and improved drinking water regulations.

The hepatitis A vaccine was introduced in 1995 and infection rates have decreased across the United States since. Vaccine recommendations initially were geared towards children in communities with a historically high risk of hepatitis A infections west of the Mississippi River and adults at high risk (eg, international travelers, men who have sex with men, people who inject drugs, and individuals with certain health problems).

Over a decade later in 2006, hepatitis A vaccination was recommended for all children >1 year. Currently, the incidence of hepatitis A infection is lowest among individuals aged 0-19 years.

However, the proportion of hepatitis A-associated hospitalizations increased between 1999 and 2011, which could be attributed to more severe disease in older adults.

“Although vaccination was never recommended for users of individual groundwater systems, this group likely benefited from the recommendations targeting children and other groups at risk. Incidence of HAV infection is now lowest among persons aged 0—19 years,” the authors of the report wrote.

Although outbreaks of hepatitis A have appeared to drop off, person-to-person transmission has ramped up in recent years. The report indicates that the number of hepatitis A cases reported to the CDC increased by 294% during 2016-2018 when compared with 2013-2015.

As of September 6, 2019, there have been 25,484 hepatitis A cases, 15,330 (60%) hospitalizations, and 254 deaths recorded in the United States since the outbreaks emerged in 2016.

“In these outbreaks, the virus is being spread from person-to-person primarily among people who use injection and non-injection drugs, people who are experiencing homelessness, and their close direct contacts. Although cases in food handlers occur, common sources of food or drinks have not been identified as potential sources of infection in the jurisdictions experiencing hepatitis A outbreaks,” CDC officials wrote on the ongoing hepatitis A outbreak information page.

As a result of the outbreaks, some states have changed required vaccination policies for school-aged children to prevent infection. Additionally, the CDC’s Advisory Committee on Immunization Practices has expanded hepatitis A vaccine recommendations to include individuals experiencing homelessness.

To stay up-to-date on the number of confirmed cases of hepatitis A in all outbreaks, be sure to check out the Contagion^® Outbreak Monitor.