Rotavirus gastroenteritis still remains a major cause of morbidity and mortality among young children in developing countries, with approximately 150,000-200,000 deaths occurring annually in sub-Saharan Africa. We reviewed papers published over the last 30 years on the epidemiology of rotavirus diarrhoea among the hospitalized and out-patient children in Kenya. The analysis shows rotavirus prevalence of 6-56% with diarrhoea occurring throughout the year and generally exhibiting distinct peaks during the dry months. Among the common genotype, G1 was the most predominant up to the year 2002 but more recently there has been an emergence of genotype G9 as the most predominant genotype and to a less extent G8. It is important to continue rotavirus surveillance in Kenya to determine accurately the burden of rotavirus disease and the emerging new genotypes. This will assist policy makers in decision making on rotavirus vaccine introduction and determining the impact of the vaccine.

An epidemiological study on the G serotype distribution of group A rotaviruses (GARV) isolated in Kenya was carried out in one urban hospital in Nairobi and in two rural hospitals in Nanyuki and Kitui to clarify the prevalent G serotypes before future introduction of the ready licensed rotavirus vaccine in Kenya. A total of 1,431 stool specimens were collected from children, who were mainly outpatients, aged from 0 to 6 years old with acute gastroenteritis from August 1991 to July 1994. Samples positive for GARV by conventional ELISA were then analyzed by subgrouping and serotyping ELISA and by PAGE. To ascertain the G serotypes of viruses in samples that were unable to be typed by serotyping ELISA, polymerase chain reaction was also attempted. The prevalence of GARV was 28.4% in the urban hospital, 22.5% in Nanyuki, and 13.7% in Kitui. Among rotavirus-positive samples, subgroup II rotaviruses were detected in 63.1%, and subgroup I rotaviruses were 25.9%. Serotype G4 was most prevalent, accounting for 41.6% followed by 23.3% of serotype G1, 17.0% of serotype G2, and serotype G3 was rarely isolated. Seven strains of serotype G8/P1B rotavirus was detected for the first time in Kenya by RT-PCR. Eleven specimens with an unusual composition of subgroup, serotype, and electropherotype were atypical GARV in which the P-serotype was P1A, P1B, or P2. Although uncommon GARV serotype G8/P1B and atypical GARV were detected, the four major GARV serotypes, G1 through G4, should be targeted at this moment for vaccination to control this diarrheal disease in Kenya. Continuous monitoring of the G- and P-serotype distribution of GARV should provide important information about the impact of rotavirus vaccination in Kenya.

Serotype G9 may be the fifth most common human rotavirus serotype, after serotypes G1 to G4. In three cross-sectional studies of childhood diarrhea, we have detected serotype G9 rotaviruses for the first time in Libya, Kenya, and Cuba. Serotype G9 constituted 27% of all rotaviruses identified, emphasizing the reemergence of serotype G9 and suggesting that future human rotavirus vaccines will need to protect against disease caused by this serotype.

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A total of 215 nontypeable rotavirus samples collected from children <5 years of age by members of the African Rotavirus Network were characterized using reverse-transcription polymerase chain reaction analysis and sequencing. The most predominant strain identified was P[8]G1 (46.9%). Genotypes P[8]G10, P[8]G8, P[6]G8, and P[7]G5 were also detected at frequencies varying from 0.5% to 2.3%. This study suggests that reassortment of unusual G types into a background of globally common genotype P[8] strains may be a major mechanism of generating rotavirus diversity. Nucleotide substitutions at the P[8], P[6], and G1 primer binding sites accounted for the failure to type these strains initially. Hence, these findings highlight the need for regular evaluation of rotavirus genotyping methods.