Lymphocytic Choriomeningitis Virus Seroprevalence among Urban Pregnant Women and Newborns, Philadelphia, Pennsylvania, USA, 2021.

Lymphocytic choriomeningitis virus (LCMV) is a globally distributed rodentborne pathogen that can cause severe congenital infections. We conducted a retrospective cross-sectional seroepidemiologic study using remnant serum samples from pregnant women and newborns at 2 hospitals in Philadelphia, Pennsylvania, USA. We tested samples for LCMV IgG and IgM in 3 phases: a high-risk group determined by neighborhood deprivation index scores, a random sample of all birthing women, and a group with prenatally diagnosed neurologic malformations. We found LCMV IgG seroprevalence was 2.4% among 700 high-risk and 2.7% among 300 randomly selected pregnant women. Seroprevalence varied by hospital site, maternal race or ethnicity, and neighborhood deprivation level. All seropositive maternal samples were IgM-negative. Thirty-seven pregnant women carrying fetuses with neurologic malformations were seronegative. Our findings highlight the risk for LCMV exposure in urban settings and emphasize the need for pregnant women to avoid contact with rodents to prevent this rare but serious congenital infection.