Abstract
Before introduction of Haemophilus influenzae type b (Hib) vaccines, rates of Hib disease in Alaska’s indigenous people were among the highest in the world. Vaccination reduced rates dramatically; however, invasive H. influenzae type a (Hia) disease has emerged. Cases of invasive disease were identified through Alaska statewide surveillance during1983–2011. Of 866 isolates analyzed for serotype, 32 (4%) were Hia. No Hia disease was identified before 2002; 32 cases occurred during 2002–2011 (p<0.001). Median age of case-patients was 0.7 years; 3 infants died. Incidence of Hia infection (2002–2011) among children <5 years was 5.4/100,000; 27 cases occurred in Alaska Native children (18/100,000) versus 2 cases in non-Native children (0.5/100,000) (risk ratio = 36, p<0.001). From 12/2009 to 12/2011, 15 cases of Hia disease occurred in southwestern Alaska (in children <5 years, rate = 204/100,000). Since introduction of the Hib conjugate vaccine, Hia infection has become a major invasive bacterial disease in Alaska Native children.
Highlights
We describe an outbreak of 15 cases of invasive H. influenzae type a (Hia) disease that occurred from December 2009 through December 2011 in neighboring areas and review the microbiology and epidemiology of
We identified 958 cases of invasive H. influenzae disease during 1983–2011; of these, 858 isolates were available for serotyping by slide agglutination
Eight additional culture-negative sterile site samples obtained from patients with clinically compatible illnesses who had been treated with antimicrobial drugs were identified, and isolates were serotyped by using PCR
Summary
Before introduction of Haemophilus influenzae type b (Hib) vaccines, rates of Hib disease in Alaska’s indigenous people were among the highest in the world. Vaccination reduced rates dramatically; invasive H. influenzae type a (Hia) disease has emerged. Cases of invasive disease were identified through Alaska statewide surveillance during1983–2011. Of 866 isolates analyzed for serotype, 32 (4%) were Hia. No Hia disease was identified before 2002; 32 cases occurred during 2002–2011 (p
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