Epidemiology of invasive Haemophilus influenzae type A disease among Navajo and White Mountain Apache children, 1988-2003.
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.
Millar
Eugene V
EV
Center for American Indian Health, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA. emillar@jhsph.edu
O'Brien
Katherine L
KL
Watt
James P
JP
Lingappa
Jairam
J
Pallipamu
Ravi
R
Rosenstein
Nancy
N
Hu
Diana
D
Reid
Raymond
R
Santosham
Mathuram
M
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
D004269:DNA, Bacterial