title: Trends in the epidemiology of invasive Haemophilus influenzae disease in Queensland, Australia from 2000 to 2013: what is the impact of an increase in invasive non-typable H. influenzae (NTHi)?
abstract: Following the introduction of vaccination against Haemophilus influenzae type b (Hib), cases of invasive encapsulated Hib disease have decreased markedly. This study aimed to examine subsequent epidemiological trends in invasive H. influenzae disease in Queensland, Australia and in particular, assess the clinical impact and public health implications of invasive non-typable H. influenzae (NTHi) strains. A multicentre retrospective study was conducted from July 2000 to June 2013. Databases of major laboratories in Queensland including Queensland Forensic and Scientific Services (jurisdictional referral laboratory for isolate typing) were examined to identify cases. Demographic, infection site, Indigenous status, serotype, and mortality data were collected. In total, 737 invasive isolates were identified, of which 586 (79·5%) were serotyped. Hib, NTHi and encapsulated non-b strains, respectively, constituted 12·1%, 69·1% and 18·8% of isolates. The predominant encapsulated non-b strains were f (45·5%) and a (27·3%) serotypes. Of isolates causing meningitis, 48·9% were NTHi, 14·9% Hib, 14·9% Hie, 10·6% Hif, 6·4% Hia and 4·3% were untyped. During the study period, there was an increase in the incidence of invasive NTHi disease (P = 0·007) with seasonal peaks in winter and spring (P 0·001) and Hib (P = 0·039) than non-Indigenous patients. In Queensland, invasive H. influenzae disease is now predominantly encountered in adults and most commonly caused by NTHi strains with demonstrated pathogenicity extending to otherwise young or immunocompetent individuals. Routine public health notification of these strains is recommended and recent available immunization options should be considered.
authors.affiliation: Department of Microbiology,Pathology Queensland,QLD,Australia.
authors.forename: J
authors.initials: J
authors.lastname: Wan Sai Cheong
authors.affiliation: Department of Microbiology,Queensland Forensic and Scientific Services,QLD,Australia.
authors.forename: H
authors.initials: H
authors.lastname: Smith
authors.affiliation: Department of Microbiology,Pathology Queensland,QLD,Australia.
authors.forename: C
authors.initials: C
authors.lastname: Heney
authors.affiliation: Department of Microbiology,Sullivan Nicolaides Pathology,QLD,Australia.
authors.forename: J
authors.initials: J
authors.lastname: Robson
authors.affiliation: University of Queensland,Brisbane,QLD,Australia.
authors.forename: S
authors.initials: S
authors.lastname: Schlebusch
authors.affiliation: University of Queensland,Brisbane,QLD,Australia.
authors.forename: J
authors.initials: J
authors.lastname: Fu
authors.affiliation: University of Queensland,Brisbane,QLD,Australia.
authors.forename: C
authors.initials: C
authors.lastname: Nourse
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000382:microbiology*; D006193:Haemophilus influenzae / Q000145:classification / Q000302:isolation & purification*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011793:Queensland / Q000453:epidemiology; D012189:Retrospective Studies; D065288:Serogroup; D016019:Survival Analysis; D055815:Young Adult
keywords: Encapsulated non-b Haemophilus influenzae; Hib; invasive H. influenzae; non-Hib; non-typable H. influenzae