Epidemiology of Haemophilus influenzae serotype A from 2000–2005, an emerging pathogen in Northern Canada and Alaska

Abstract number: 1732_155

Hennessy T., Bruce M., Deeks S., Cottle T., Palacios C., Case C., Hemsley C., Lovgren M., Sobol I., Corriveau A., Larke B., Debyle C., Harker-Jones M., Hurlburt D., Peters H., Parkinson A.

Background: Prior to introduction of the Haemophilus influenzae type b (Hib) conjugate vaccines, rates of Hib disease among aboriginal people living in Alaska (AK) and Northern Canada (N Can) were among the highest reported in the world. Routine vaccination has reduced these rates to very low levels; however, serotype replacement with non-type b strains may result in a reemergence of invasive disease in children.

Methods: We reviewed population-based data on invasive Hi disease in AK and N Can collected from 2000–2005 through the International Circumpolar Surveillance (ICS) network. Chart reviews were conducted on laboratory-confirmed cases using standardised forms to verify illness episode information. All Hia isolates were characterised using pulsed-field gel electrophoresis (PFGE). AK and N Can estimated populations as of 2005 were 655,435 and 132,956 respectively; aboriginal peoples comprised 19% of the population in AK and 59% in N Can.

Results: During the study period, a total of 138 cases of invasive Hi disease were reported from AK (76) and N Can (62). Among the 88 (67%) invasive Hi cases with serotype information available, 42 (48%) were serotype a, 27 (31%) were serotype b, 12 (14%) were serotype f. Among Hia isolates, 35 (83%) occurred in aboriginal peoples; median age was 1.1 years (range 3 mo to 74 years); 62% were male. Two Hia cases (1 adult/1 child) were fatal. Common clinical presentations included: meningitis (33%), pneumonia (29%), and septic arthritis (12%). There were no cases of epiglotittis. Overall annual Hia incidence was 0.9 cases per 100,000 population. Annual incidence rates in aboriginals in AK and N Can were 1.1 and 4.6 per 100,000 persons, respectively; rates in aboriginal children <2 years of age were 22 and 101 cases per 100,000 persons, respectively. PFGE analysis revealed genetically similar Hia strains in both AK and N Can.

Conclusions: Serotype a is now the most common Hi serotype seen in the North American Arctic, with the highest rates among indigenous children. Further research is needed to determine sequelae, risk factors, outbreak potential, and the utility of chemoprophylaxis for this disease.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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