title: Epidemiology of invasive Haemophilus influenzae type A disease among Navajo and White Mountain Apache children, 1988-2003.
abstract: BACKGROUND
  Before the introduction of Haemophilus influenzae type b (Hib) conjugate vaccines, rates of H. influenzae disease among Navajo and White Mountain Apache (WMA) children were among the highest reported worldwide. Routine Hib vaccination has significantly reduced rates of Hib disease in these populations. As Hib disease rates decrease to very low levels, there are concerns that non-type b strains of H. influenzae may emerge as more prevalent causes of invasive disease in children.
  
  
  METHODS
  We reviewed population-based, active laboratory surveillance data from the period of 1988-2003 for invasive H. influenzae type a (Hia) disease among Navajo and WMA children aged <5 years. Clinical information on cases was collected by chart review. A sample of Hia isolates from Navajo children was typed by pulsed-field gel electrophoresis (PFGE).
  
  
  RESULTS
  During 1988-2003, a total of 76 reported cases of invasive Hia disease occurred among Navajo and WMA children. The overall annual incidence was 20.2 cases per 100,000 population aged <5 years. There was no increase in Hia disease rates after Hib vaccination was introduced. The median age of patients was 12 months. Meningitis (50% of cases) was the most common presentation, followed by pneumonia (27.6%). Two children with Hia disease died. PFGE analysis revealed a limited genetic diversity of Hia strains in this population.
  
  
  CONCLUSIONS
  Active surveillance data showed high rates of invasive Hia disease among Navajo and WMA children but no increase in the incidence after Hib vaccination was introduced. The presentation of Hia disease is similar to that of Hib disease in the prevaccine era.
authors.affiliation: Center for American Indian Health, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA. emillar@jhsph.edu
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Millar
authors.forename: Katherine L
authors.initials: KL
authors.lastname: O'Brien
authors.forename: James P
authors.initials: JP
authors.lastname: Watt
authors.forename: Jairam
authors.initials: J
authors.lastname: Lingappa
authors.forename: Ravi
authors.initials: R
authors.lastname: Pallipamu
authors.forename: Nancy
authors.initials: N
authors.lastname: Rosenstein
authors.forename: Diana
authors.initials: D
authors.lastname: Hu
authors.forename: Raymond
authors.initials: R
authors.lastname: Reid
authors.forename: Mathuram
authors.initials: M
authors.lastname: Santosham
mesh_terms: D001130:Arizona / Q000453:epidemiology; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000235:genetics; D005260:Female; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000382:microbiology*; D006193:Haemophilus influenzae / Q000145:classification* / Q000235:genetics; D006801:Humans; D007198:Indians, North American; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009516:New Mexico / Q000453:epidemiology; D010802:Phylogeny; D013997:Time Factors; D014589:Utah / Q000453:epidemiology
chemical_list: D004269:DNA, Bacterial