title: 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: BACKGROUND
  High 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.
  
  
  METHODS
  During 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.
  
  
  RESULTS
  In 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.
  
  
  CONCLUSIONS
  This 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.
authors.affiliation: Global Disease Detection Division, Kenya Office of the US Centers for Disease Control and Prevention, Nairobi, Kenya.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Breiman
authors.forename: Leonard
authors.initials: L
authors.lastname: Cosmas
authors.forename: Henry
authors.initials: H
authors.lastname: Njuguna
authors.forename: Allan
authors.initials: A
authors.lastname: Audi
authors.forename: Beatrice
authors.initials: B
authors.lastname: Olack
authors.forename: John B
authors.initials: JB
authors.lastname: Ochieng
authors.forename: Newton
authors.initials: N
authors.lastname: Wamola
authors.forename: Godfrey M
authors.initials: GM
authors.lastname: Bigogo
authors.forename: George
authors.initials: G
authors.lastname: Awiti
authors.forename: Collins W
authors.initials: CW
authors.lastname: Tabu
authors.forename: Heather
authors.initials: H
authors.lastname: Burke
authors.forename: John
authors.initials: J
authors.lastname: Williamson
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Oundo
authors.forename: Eric D
authors.initials: ED
authors.lastname: Mintz
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Feikin
mesh_terms: D000349:Africa / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D012424:Rural Population; D014435:Typhoid Fever / Q000453:epidemiology* / Q000517:prevention & control*; D014436:Typhoid-Paratyphoid Vaccines / Q000627:therapeutic use*; D014505:Urban Population
chemical_list: D014436:Typhoid-Paratyphoid Vaccines