Hepatitis A virus (HAV) is an RNA picornavirus and humans are its only known reservoir.1 The virus infects the liver and is then secreted into feces where it is present from 2 weeks before until about a week after symptom onset.2 HAV can persist on environmental surfaces and is resistant to the processes usually used to eliminate bacterial pathogens from food.3 It is transmitted through the fecal-oral route, for example by ingesting food or water contaminated with the feces of an infected person, touching a contaminated surface or objects, or having sexual contact with an infected partner.4 Vaccination is recommended for persons at increased risk for hepatitis A, including persons traveling to or working in countries that have high or intermediate rates of infection, MSM, IDUs, persons experiencing homelessness, and persons with occupational risk of infection.5 Vaccination is also recommended for persons with clotting-factor disorders, although changes in clotting factor preparation and donor screening have markedly reduced the risk in this group.
Outbreaks Among Homeless Persons
The hepatitis A outbreak in LA County among persons experiencing homelessness or using illicit drugs followed a large outbreak among these risk groups in San Diego County that began in November 2016. In San Diego County between November 2016 and the end of the outbreak in January 2018, there were 592 hepatitis A cases, including 20 (3.4%) deaths; most persons who died had underlying liver disease, often from hepatitis C.6 Almost 69% of San Diego cases were hospitalized. Three-quarters of the cases occurred among those were homeless and/or reported IDU. San Diego cases also occurred among persons who provided services to or had significant contact with the homeless, including volunteers at shelters and sanitation workers. Health officials in Santa Cruz County also identified an increase in hepatitis A cases with most occurring among the same risk groups.6
Beginning in May 2017, cases of hepatitis A were observed among persons in LA County who had recent exposure in San Diego or Santa Cruz County. LA County health officials declared a hepatitis A outbreak among persons who were homeless or using illicit drugs in September 2017. The final outbreak-associated case in LA County was in January 2018. Between May 2017 and January 2018 there were a total of 18 outbreak associated cases, 12 hospitalizations, and no deaths (see LAC DPH Hepatitis A Outbreak webpage for more information). Since January 2018, sporadic cases and small outbreaks of hepatitis A have continued to occur in LA County among persons with a history of homelessness or IDU.
Increased Risk Among MSM
In addition to the LA County outbreak among homeless persons and IDUs, there was an increase in hepatitis A illness among MSM. Locally in 2017, there were 23 confirmed cases among MSM compared with 9 cases in 2016 and no reported cases in 2015. Several of the LA County MSM cases reported travel to San Diego or other U.S. and international locations with ongoing outbreaks. Between 2016 and 2018, several European Union/European Economic Area (EU/EEA) countries experienced large outbreaks of hepatitis A infections mainly affecting MSM.7,8 In the U.S. during the same time frame, hepatitis A outbreaks in MSM were identified in New York City and Colorado while San Francisco experienced an increase in hepatitis A cases among MSM.9,10 The number of hepatitis A cases among MSM in LA County declined in 2018 with a total of 8 cases reported.
Healthcare providers should be aware that MSM continue to be at increased risk for hepatitis A and should routinely promote hepatitis A vaccination.