PREVALENCE OF HUMAN CALICIVIRUS INFECTIONS IN KENYA AS DETERMINED BY ENZYME IMMUNOASSAYS FOR 3 GENOGROUPS OF THE VIRUS

An epidemiological survey on human calicivirus (HuCV) infections and a ssociated gastroenteritis in infants was conducted to clarify the prev alence of HuCV infections in infants and adults in Kenya. Enzyme immun o assays (EIAs) for three genogroups of HuCVs, Norwalk virus (NV), Mex ico virus (MXV), and Sapporo virus (SV), were used to detect antigen o r antibody. We tested 1,431 stool samples obtained from children young er than 6 years old with acute gastroenteritis who visited outpatient clinics in three districts in Kenya from August 1991 to July 1994. Thi rty-two (2.2%) of these stool samples were positive for SV antigen. On ly one (0.1%) of 1,186 samples was positive for NV antigen and none of 246 samples was positive for MXV antigen. One hundred ninety-three se rum samples were tested for antibodies to NV and MXV, and 64 of them w ere examined for antibody to SV. The pattern of the age-related preval ence of serum antibody to NV was different from that of antibodies to MXV and SV. The acquisition of serum antibodies to HuCVs in the three genogroups appeared in early childhood, at about 1 to 2 years of age. The prevalence of serum antibody to NV was low (about 60%) throughout adulthood compared with a high prevalence of antibody (similar to 80 t o 90%) to MXV and SV. These data indicate that infections with viruses in the three genogroups of HuCVs are common in Kenya, and immunologic al responses to NV may be different from those to MXV and SV. The EIAs for the detection of NV and MXV antigens appear to be quite specific for prototype NV and MXV strains, respectively, so that they can detec t only a few strains of HuCVs related to them. Alternatively, NV and M XV caused less severe infections that did not bring children to the ou tpatient clinics for gastroenteritis in Kenya.