Patients admitted with fever to four Liberian hospitals were tested for Lassa fever (LF) by means of the indirect fluorescenr antibodv technique and by virus isolation. The incidence of LF and presumptive LF among consecutive febri!e adult patients was I4% and !7% in two hospitals located in the interior; no cases of LF were found among 24 consecuctive 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 l30% to 36%. Lassa virus was isolated from l7 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 acilve virus and its subsequent recovery in an appropriate laboratory.