118 Invasive Disease Caused by Haemophilus Influenzae Species in 12 Impact Centers, 1996–2001

Haemophilus influenzae type b (Hib) invasive disease has declined in Canada due to infant immunization programs. A retrospective study was conducted at 12 IMPACT centers to determine the role of non-b serotypes (H. influenzae types a,c,d,e,f or Hia to Hif, and non-typeable species or Hi-nt) in invasive disease caused by this species. Clinical and demographic data were collected for all laboratory identified cases of H. influenzae cultured from normally sterile sites (blood, cerebrospinal fluid, pleural fluid, joint aspirate, etc) from Jan 1, 1996 to Dec 31, 2001. A total of 166 cases were identified, of which 58 (34.9%) were due to Hib. The information below pertains only to the 108 non-b cases, of which 25 (23.1%) were due to Hia, 4 (3.7%) due to Hid, 2 (1.9%) due to Hie, 11 (10.2%) due to Hif, 47 (43.5%) due to Hi-nt, and 19 (17.6%) were incompletely typed. Sixty three (58.3%) cases were male. The ethnic background was available for 57 mothers and/or fathers: 42% were Caucasian, 40% aboriginal, 4% African and 7% Asian; the remainder were unknown. The mean age at presentation was 3.1 years (range 0 days - 17 years). Fifty patients (46.3%) were 12 months of age or younger, 19 (17.6%) were 13–24 months, 17 (15.7%) were 25–60 months, and 22 (20.4%) were greater than 5 years of age. The most commonly reported clinical syndromes were pneumonia in 37 (23.6%), meningitis in 29 (18.5%), and isolated bacteremia in 17 (10.8%). Pneumonia was caused by Hi-nt in 20/37 (54%), Hia in 5/37 (14%), and Hif in 4/37 (11%), whereas meningitis was caused by Hia in 13/29 (45%), Hi-nt in 8/29 (28%) and Hif in 4/29 (14%). Mean duration of hospital stay was 11.5 days (105 patients), and mean time spent in the pediatric intensive care was 5.8 days (42 patients). Eight patients died, of whom 5 (4 with meningitis, 1 with pneumonia) were attributed to the H. influenzae infection. Of the 100 survivors, 83 (83%) had fully recovered or improved by hospital discharge, 7 required anticonvulsants, 6 had hearing impairment, and 5 had other neurological abnormalities.