Invasive Haemophilus influenzae in the United States, 1999-2008: epidemiology and outcomes.
OBJECTIVE
Introduction of the Haemophilus influenzae type b (Hib) conjugate vaccine has resulted in a dramatic reduction of Hib disease in the U.S. and an increase in the relative importance of infections caused by nontypeable strains. The current project describes the characteristics and clinical outcomes of pediatric and adult patients with invasive H. influenzae (HI) and, through multivariable analysis, identifies risk factors for in-hospital mortality.


METHODS
HI cases were identified during 1999-2008 through active surveillance as part of active bacterial core surveillance (ABCs). Multivariable analysis was performed with logistic regression to identify factors predictive of in-hospital death.


RESULTS
4839 cases of HI were identified from 1999-2008. Children accounted for 17.1% of cases and adults 82.9%. Underlying conditions were present in 20.7% of children and 74.8% of adults. In-hospital mortality was highest in cases ≥65 years (21.9%) and <3 months (16.2%). The risk of in-hospital death in children <1 year was higher among those who were prematurely-born (<28 weeks, OR 7.1, 95% CI 3.2-15.6; 28-36 weeks OR 2.1, 95% CI 0.9-4.8) and, among children aged 1-17 years, higher in those with healthcare-associated onset and dialysis (OR 5.66, 95% CI 1.84-17.39; OR 18.11, 95% CI 2.77-118.65). In adults, age ≥40 was associated with death in nontypeable, but not encapsulated, infections. Infections with nontypeable strains increased the risk of death in cases ≥65 years (OR 1.81, 95% CI 1.31-2.52). Healthcare-associated HI, bacteremia without identifiable focus, bacteremic pneumonia, associated cirrhosis, cerebrovascular accident, dialysis, heart failure, and non-hematologic malignancy also increased the risk of death in adults.


CONCLUSIONS
Prematurity in infants, advanced age and certain chronic diseases in adults were associated with an increased risk of in-hospital death. Nontypeable HI was associated with higher mortality in the elderly.
Department of Medicine, Emory University School of Medicine, The Atlanta VA Medical Center, 1670 Clairmont Road, Mail Code 151-ID, Atlanta, GA 30333, USA. dlivorsi@iupui.edu
Daniel J
DJ
Livorsi
Jessica R
JR
Macneil
Amanda C
AC
Cohn
Joseph
J
Bareta
Shelly
S
Zansky
Susan
S
Petit
Ken
K
Gershman
Lee H
LH
Harrison
Ruth
R
Lynfield
Arthur
A
Reingold
William
W
Schaffner
Ann
A
Thomas
Monica M
MM
Farley
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology / Q000628:therapy; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology / Q000628:therapy; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000628:therapy; D006193:Haemophilus influenzae / Q000145:classification / Q000302:isolation & purification* / Q000472:pathogenicity; D017052:Hospital Mortality; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008875:Middle Aged; D011159:Population Surveillance; D012307:Risk Factors; D012703:Serotyping; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology