Population-Based Incidence of Typhoid Fever in an Urban Informal Settlement and a Rural Area in Kenya: Implications for Typhoid Vaccine Use in Africa

Abstract

BackgroundHigh rates of typhoid fever in children in urban settings in Asia have led to focus on childhood immunization in Asian cities, but not in Africa, where data, mostly from rural areas, have shown low disease incidence. We set out to compare incidence of typhoid fever in a densely populated urban slum and a rural community in Kenya, hypothesizing higher rates in the urban area, given crowding and suboptimal access to safe water, sanitation and hygiene.MethodsDuring 2007-9, we conducted population-based surveillance in Kibera, an urban informal settlement in Nairobi, and in Lwak, a rural area in western Kenya. Participants had free access to study clinics; field workers visited their homes biweekly to collect information about acute illnesses. In clinic, blood cultures were processed from patients with fever or pneumonia. Crude and adjusted incidence rates were calculated.ResultsIn the urban site, the overall crude incidence of Salmonella enterica serovar Typhi (S. Typhi) bacteremia was 247 cases per 100,000 person-years of observation (pyo) with highest rates in children 5–9 years old (596 per 100,000 pyo) and 2–4 years old (521 per 100,000 pyo). Crude overall incidence in Lwak was 29 cases per 100,000 pyo with low rates in children 2–4 and 5–9 years old (28 and 18 cases per 100,000 pyo, respectively). Adjusted incidence rates were highest in 2–4 year old urban children (2,243 per 100,000 pyo) which were >15-fold higher than rates in the rural site for the same age group. Nearly 75% of S. Typhi isolates were multi-drug resistant.ConclusionsThis systematic urban slum and rural comparison showed dramatically higher typhoid incidence among urban children <10 years old with rates similar to those from Asian urban slums. The findings have potential policy implications for use of typhoid vaccines in increasingly urban Africa.

Household Water Treatment Uptake during a Public Health Response to a Large Typhoid Fever Outbreak in Harare, Zimbabwe

“…19 Although some outbreaks have occurred in rural areas, others have struck residents of national capitals, such as Kinshasa and Lusaka, and the disease has become endemic in some parts of Nairobi (Clark and others, unpublished data). [20][21][22] The PFGE patterns of strains from the Harare outbreak in 2011-12 were indistinguishable from or highly similar (1 or 2 bands different) to those from an earlier outbreak in Harare and to strains from Malawi and Tanzania, suggesting persistence of these strains over time in Zimbabwe and dispersion across southern and eastern Africa. The recent evidence of the magnitude of epidemic and endemic typhoid fever in sub-Saharan African countries highlights the continued importance of typhoid fever prevention and control in this region.…”

Access to Waterless Hand Sanitizer Improves Student Hand Hygiene Behavior in Primary Schools in Nairobi, Kenya

“…Households in this area also exhibit high rates of pneumonia and diarrheal disease. [27][28][29] All primary schools within the surveillance area were visited to obtain information on their student population as well as current water supply, sanitation, and hygiene services. Schools with more than 100 students were considered eligible for the study to ensure balance of school populations across treatment arms.…”

Soil-Transmitted Helminths in Pre-School-Aged and School-Aged Children in an Urban Slum: A Cross-Sectional Study of Prevalence, Distribution, and Associated Exposures

“…The IEIP methods have been described elsewhere 34 ; briefly, the program enrolls all consenting adults and children with head-of-household consent who have been living in all households in the study area for at least 4 months, thus attempting to enroll a census of all residents; the household refusal rate is under 2%. 35 The IEIP conducts at least biweekly visits to all enrolled households, to record interval self-reported morbidity and health care usage data. The IEIP maintains an up-to-date registry by continually approaching new arrivals in all community households for enrollment and updating records to reflect outmigration.…”