The epidemiology of invasive disease due to Haemophilus influenzae serotype a in the Canadian North from 2000 to 2010

INTRODUCTION: The International Circumpolar Surveillance (ICS) project is a population-based surveillance network. Since 2000, Canada has participated in the ICS Invasive Bacterial Disease Working Group's surveillance of invasive disease due to Haemophilus influenzae (Hi). METHODS: A standardized case report form containing demographic and clinical information was completed for all reported Hi cases in the study regions. Isolates were sent to a reference laboratory for confirmation and serotyping. Analysis was conducted on all Hi serotype a (Hia) cases reported from 2000 to 2010. The northern Canadian population was estimated using Statistics Canada information. RESULTS: Of the 130 Hi cases reported from 2000 to 2010, 72 (56% of cases with serotype information) were due to Hia. The number of Hia cases reported each year ranged from 2 in 2008 to 13 in 2010. The average Hia incidence over the 11 years was 4.6 cases per 100,000 population per year. The majority of Hia occurred in infants less than 2 years of age (73% of cases). This age group had an average annual incidence of 87.5 cases per 100,000 population. Among cases for which ethnicity was indicated, 91% of Hia cases reported Aboriginal status with the average incidence being 6.9 cases per 100,000 population per year. The most common clinical presentation was meningitis (reported in 37% of cases), followed by bacteraemia (34%) and pneumonia (27%). More than 90% of cases were hospitalized, and there were 4 deaths, resulting in a case fatality ratio of 5.6%. CONCLUSION: In the last decade, Hia has become an important cause of morbidity and mortality in the Canadian North. More detailed surveillance information from a national perspective is needed. Further work on vaccine development should be encouraged.