Lassa virus antibodies in hospital personnel in western Liberia

The sera of 844 Liberian hospital staff memebers were positive for Lassa Virus (LV) antibodies in a survey using the indirect fluorescent antibody technique (IFAT). In two hospitals in Lofa County near the Sierra Leone border, the prevalence, 15.4%, was significantly higher than the 8.4% in seven others. There were near differences between the prevalence among laboratory workers, 15.3%, and other workers, 7.7%, and between midwifery students, 21.2%, and midwives, 4.2%, suggesting their infection from patients or their blood products. However, the over-all prevalence among those with patient contacts was the same as that among those without direct patient contact; most LV infections were apparently acquired from sources other than patients in hospital. This finding, the lack of evidence of hospital outbreaks and the presence of comparable prevalences in all age groups suggest that LV infections occur on a continuing basis in this population. In one hospital the comparison of the results of IFAT and complement fixation tests revealed some who reacted by one technique and not by the other. In one person the titre by IFAT had dropped from 1:32 to undetectable levels in two years. This finding prompts caution in the interpretation of results.