284. Using Epidemiologic Investigation and Viral Sequencing to Describe and Provide Public Health Response to an Outbreak (OB) of Acute Hepatitis A Virus Infection (HAV) in the San Fernando Valley (SFV), California

BACKGROUND: California (CA) experienced a large hepatitis A OB in 2017–2018 associated with genotype IB strains, primarily among persons experiencing homelessness and/or using drugs. In October and November 2018, we identified a cluster of three HAV cases among persons linked by drug use and homelessness in the San Fernando Valley (SFV), CA. We describe how molecular epidemiologic methods linked an additional four OB cases that lived or were associated with a senior housing facility (SHF) and guided hepatitis A vaccine outreach. METHODS: Suspect HAV cases were reported to DPH through provider and electronic lab reports with positive serum HAV IgM and resided in a 2 mile(2) area in SFV. A case report and extended interview were completed on suspects to assess risk factors associated with HAV transmission and contacts. HAV IgM positive serum specimens were sent to the CA DPH Viral and Rickettsial Disease Laboratory for HAV RNA detection and molecular sequencing. Extracted nucleic acids were amplified using nested, RT-PCR targeting the VP1-P2B region, and a 315 nt fragment was sequenced using Sanger sequencing. Contacts to cases received HAV prophylaxis and HAV vaccine outreaches occurred in at-risk settings. RESULTS: We identified 7 HAV cases with symptom onsets from October 2018 to January 2019. All 7 cases had positive serum HAV IgM, ≥ALT 3 X normal or had a specimen matching the OB strain and were epi- linked to a case previously identified. Of 3 homeless cases, 2 had genotype 1B, CA cluster A; one specimen was unavailable. Four additional SHF cases were 2 residents, one staff, and one visitor. Among the 4 cases associated with the SHF, three had genotype 1B, CA cluster A; one specimen was unavailable. Two elderly residents reported severe fatigue, without nausea, diarrhea and vomiting. Among the 3 homeless individuals, no direct link to the SHF was established. In total, 948 HAV vaccines were provided at the SHF, homeless shelters and other settings. HAV vaccine coverage for SHF residents and food handlers was 70% and 62%,, respectively. CONCLUSION: Two clusters of HAV cases were identified among homeless persons and individuals associated with an SHF were linked through a common HAV genotype. Two elderly cases had atypical symptoms that may not have been confirmed as HAV without viral sequencing and prompted vaccine campaign to prevent additional HAV cases. DISCLOSURES: All authors: No reported disclosures.