Peter M. Tukei

Epidemiological study of the G serotype distribution of group A rotaviruses in Kenya from 1991 to 1994.

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. J. Med. Virol. 58:296–303, 1999.

Laboratory diagnosis of Ebola hemorrhagic fever during an outbreak in Yambio, Sudan, 2004.

Between the months of April and June 2004, an Ebola hemorrhagic fever (EHF) outbreak was reported in Yambio county, southern Sudan. Blood samples were collected from a total of 36 patients with suspected EHF and were tested by enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G and M antibodies, antigen ELISA, and reverse-transcription polymerase chain reaction (PCR) of a segment of the Ebolavirus (EBOV) polymerase gene. A total of 13 patients were confirmed to be infected with EBOV. In addition, 4 fatal cases were classified as probable cases, because no samples were collected. Another 12 patients were confirmed to have acute measles infection during the same period that EBOV was circulating. Genetic analysis of PCR-positive samples indicated that the virus was similar to but distinct from Sudan EBOV Maleo 1979. In response, case management, social mobilization, and follow-up of contacts were set up as means of surveillance. The outbreak was declared to be over on 7 August 2004.

Yellow Fever Outbreak, Imatong, Southern Sudan

In May 2003, the World Health Organization received reports about a possible outbreak of a hemorrhagic disease of unknown cause in the Imatong Mountains of southern Sudan. Laboratory investigations were conducted on 28 serum samples collected from patients in the Imatong region. Serum samples from 13 patients were positive for immunoglobulin M antibody to flavivirus, and serum samples from 5 patients were positive by reverse transcription–polymerase chain reaction with both the genus Flavivirus–reactive primers and yellow fever virus–specific primers. Nucleotide sequencing of the amplicons obtained with the genus Flavivirus oligonucleotide primers confirmed yellow fever virus as the etiologic agent. Isolation attempts in newborn mice and Vero cells from the samples yielded virus isolates from five patients. Rapid and accurate laboratory diagnosis enabled an interagency emergency task force to initiate a targeted vaccination campaign to control the outbreak.

Epidemic yellow fever in eastern Nigeria, 1986

An epidemic of yellow fever occurred in the eastern part of Nigeria during the second half of 1986. Oju, in Benue State, was the most heavily affected region, but yellow fever also occurred in surrounding areas, particularly Ogoja, in Cross River State. In Oju, the mean attack and mortality rates were 4.9% and 2.8%, respectively. Sex and age specific rates were highest in males and in the 20-29 yr age group. The overall case fatality rate was approximately 50%. Diagnosis was confirmed by IgM capture enzyme-linked immunosorbent assay (ELISA) and complement fixation (CF) tests. Entomological investigations implicated Aedes africanus as the epidemic vector. Oju alone probably had about 9800 cases of yellow fever with jaundice, and some 5600 deaths. Outbreaks of this nature could be prevented by inclusion of yellow fever in the Expanded Programme on Immunisation, in areas subject to recurrent epidemics.

Limited duration of vaccine poliovirus and other enterovirus excretion among human immunodeficiency virus infected children in Kenya

BackgroundImmunodeficient persons with persistent vaccine-related poliovirus infection may serve as a potential reservoir for reintroduction of polioviruses after wild poliovirus eradication, posing a risk of their further circulation in inadequately immunized populations.MethodsTo estimate the potential for vaccine-related poliovirus persistence among HIV-infected persons, we studied poliovirus excretion following vaccination among children at an orphanage in Kenya. For 12 months after national immunization days, we collected serial stool specimens from orphanage residents aged <5 years at enrollment and recorded their HIV status and demographic, clinical, immunological, and immunization data. To detect and characterize isolated polioviruses and non-polio enteroviruses (NPEV), we used viral culture, typing and intratypic differentiation of isolates by PCR, ELISA, and nucleic acid sequencing. Long-term persistence was defined as shedding for ≥ 6 months.ResultsTwenty-four children (15 HIV-infected, 9 HIV-uninfected) were enrolled, and 255 specimens (170 from HIV-infected, 85 from HIV-uninfected) were collected. All HIV-infected children had mildly or moderately symptomatic HIV-disease and moderate-to-severe immunosuppression. Fifteen participants shed vaccine-related polioviruses, and 22 shed NPEV at some point during the study period. Of 46 poliovirus-positive specimens, 31 were from HIV-infected, and 15 from HIV-uninfected children. No participant shed polioviruses for ≥ 6 months. Genomic sequencing of poliovirus isolates did not reveal any genetic evidence of long-term shedding. There was no long-term shedding of NPEV.ConclusionThe results indicate that mildly to moderately symptomatic HIV-infected children retain the ability to clear enteroviruses, including vaccine-related poliovirus. Larger studies are needed to confirm and generalize these findings.

Hepatitis E Among Refugees in Kenya: Minimal Apparent Person-to-person Transmission, Evidence for Age-dependent Disease Expression, and New Serologic Assays

In 1991, a large outbreak of hepatitis E occurred among refugees in Kenya. The overall clinical attack rate in the refugee camp was 6.3% (1702/26920). The primary attack rate in the entire refugee camp (4.8%) and the secondary attack rate in case-households (4.4%) were similar. Three recently developed tests were used for this investigation, including a synthetic peptide-based enzyme immuno-assay (EIA) to detect IgG antibody to hepatitis E virus (anti-HEV) and Western blot assays to detect IgG and IgM anti-HEV. In a sample of 132 case-patients, IgG anti-HEV was detected in 101 (77%) by peptide EIA and 96 (73%) by Western blot; the concordance between EIA and Western blot was 91%. Our findings suggest that >50% of HEV infections may have been anicteric and the expression of icterus with HEV infection was age-dependent. Moreover, in spite of poor hygienic conditions present in the refugee camp, little person-to-person transmission was apparent in households.

Characterization of Human Rotavirus Strains from Children with Diarrhea in Nairobi and Kisumu, Kenya, between 2000 and 2002

Rotavirus infection is a major cause of diarrheal illness and hospitalization in children <5 years old in Kenya and has been described in various settings and locations across the country and for different time points. In this study, we expand on the molecular characterization of rotavirus strains collected in Nairobi and Kisumu, Kenya, between 2000 and 2002. Rotavirus strains were typed by reverse-transcription polymerase chain reaction and characterized using VP6 monoclonal antibodies and RNA electrophoresis of the viral genome. A large proportion of specimens could not be genotyped; 41% did not produce a G type result, and 43% did not produce a P type result. Of the strains that could be genotyped, G1P[8] strains were predominant, followed by G2P[4] strains. In addition, G8 and G9 strains were seen in similar proportions Interestingly, the G and P combinations were more diverse among G8 and G9 rotavirus strains, suggesting the recent introduction of these strains into the human population. These observations are a link between the occasional observation of G8 and G9 strains at the turn of the century and the high predominance of G9P[8] strains observed in Kenya in 2005.

Rubella seroprevalence among primary and pre-primary school pupils at Moi's Bridge location, Uasin Gishu District, Kenya.

BackgroundRubella is an infectious and generally mild childhood viral disease. The disease is of public health importance because infection acquired during early pregnancy often results in foetal abnormalities that are classified as congenital rubella syndrome (CRS). The burden of rubella infection in most developing countries in not well documented because of limited epidemiological data. However, availability of an effective vaccine has made it necessary to have all the countries with no routine vaccination schedule to evaluate the burden of disease in order to make informed decisions on rubella vaccination and strategy. To address this gap we conducted a study to determine age-specific rubella seroprevalence rates and related risk factors among primary and pre-primary school children in Uasin Gishu district, Mois Bridge location of Kenya.MethodsSubjects of the study were 498 pupils from seven primary schools aged 4–20 years. Questionnaire surveys with blood sampling were conducted between January to July 2005. Samples were tested for rubella specific IgG antibody using ELISA test kit (Enzygnost® Behring, Germany).ResultsOverall, rubella seropositivity rate was 80% and it increased with age from 59% (among ages 4–6 years) to 94% (ages 14–20 years). Multivariate logistic regression analysis model, showed that age of child and ownership of a television set which is a proxy measure of socio-economic status of family were significantly associated with rubella seropositivity. The odds of rubella seropositivity in a child older than 13 years was more than that in children younger than 7 years (OR = 3.8 95% CI 2.56–5.78). The odds of rubella seropositivity in a child whose family did not own a television set was 3 times higher than that of child whose family owned a set (OR 3.06, 95% CI 1.17–7.97).ConclusionThe study provides important and highly useful information on rubella age specific seroprevalence rates in Kenya. Advancing age was found to be associated with increased risk of rubella. Low socio-economic factors suggest an increased risk of infection in certain categories of society, and control measures need to target this. Overall, the findings can also be used by policy makers to model introduction of routine rubella vaccination in the country and also other developing countries facing similar challenges. More than half of the children got infected in pre-primary and efforts to control rubella should target pre-school children. These data provides pre-vaccination information that can be used to guide immunization strategy as well as to determine success of an immunization programme.

REACTIVITIES OF ANTIBODIES TO HIV AND SIV IN HUMAN SERA IN KENYA, GABON, AND GHANA

The isolation of simian immunodeficiency virus (SIV) from African non-human primates and 2 new human retroviruses from people in West Africa (HIV-2 and HTLV-IV) which are antigenically closely related to SIV indicate the importance of viral ecological studies on HIV/SIV especially in Africa. This is a report on reactivity with the antigens of SIV derived from African green monkey and HIV-1 of antibodies in 29 anti-HIV-positive human sera from East and West Africa. SIV shares antigenicity with the gag gene products of HIV-1 but not with its envelope gene protein products. Of the 29 sera 12 were from patients with AIDS or AIDS-related complex (ARC) in Kenya 5 from apparently healthy people in Gabon and 12 from prostitutes manifesting ARC in Ghana. From the serological findings it is conceivable that the antibody-positive people in Kenya are infected with a virus that is antigernically similar to prototype HIV (HIV-1) while those in Gabon and Ghana are infected with a virus that is closely related to SIV such as GTLV-IV or or HIV-2. To test this idea isolates from these seropositive persons were obtained in Kenya and Ghana. Analysis of viral proteins and genomes revealed that the Kenyan isolates were indistinguishable from the prototype HIV-1 group whereas the Ghanaian isolate belongs to the HIV-2 virus group.