Endemic Lassa fever in Liberia. II. Serological and virological findings in hospital patients.

Patients admitted with fever to four Liberian hospitals were tested for Lassa fever (LF) by means of the indirect fluorescent antibody technique and by virus isolation. The incidence of LF and presumptive LF among consecutive febrile adult patients was 14% and 17% in two hospitals located in the interior; no cases of LF were found among 24 consecutive patients in a hospital near the coast. In the three inland hospitals the incidence of confirmed or presumptive LF among the patients in whom the diagnosis was seriously considered varied from 13% to 36%. Lassa virus was isolated from 17 patients out of the 59 cases found in this survey. LF is a common cause of fever in northern Liberia. The diagnosis depends upon the readiness of the staff to consider the diagnosis, the collection of blood specimens at appropriate times, and the preservation of sera at sub-freezing temperatures to permit survival of active virus and its subsequent recovery in an appropriate laboratory.