title: Temporal cross-correlation between influenza-like illnesses and invasive pneumococcal disease in The Netherlands.
abstract: While the burden of community-acquired pneumonia and invasive pneumococcal disease (IPD) is still considerable, there is little insight in the factors contributing to disease. Previous research on the lagged relationship between respiratory viruses and pneumococcal disease incidence is inconclusive, and studies correcting for temporal autocorrelation are lacking.
  
  
  
  To investigate the temporal relation between influenza-like illnesses (ILI) and IPD, correcting for temporal autocorrelation.
  
  
  
  Weekly counts of ILI were obtained from the Sentinel Practices of NIVEL Primary Care Database. IPD data were collected from the Dutch laboratory-based surveillance system for bacterial meningitis from 2004 to 2014. We analysed the correlation between time series, pre-whitening the dependent time series with the best-fit seasonal autoregressive integrated moving average (SARIMA) model to the independent time series. We performed cross-correlations between ILI and IPD incidences, and the (pre-whitened) residuals, in the overall population and in the elderly.
  
  
  
  We found significant cross-correlations between ILI and IPD incidences peaking at lags -3 overall and at 1 week in the 65+ population. However, after pre-whitening, no cross-correlations were apparent in either population group.
  
  
  
  Our study suggests that ILI occurrence does not seem to be the major driver of IPD incidence in The Netherlands.
authors.affiliation: Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Wilke
authors.initials: W
authors.lastname: Hendriks
authors.affiliation: Department for Statistics, Informatics and Modeling, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Hendriek
authors.initials: H
authors.lastname: Boshuizen
authors.affiliation: Department for Statistics, Informatics and Modeling, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Arnold
authors.initials: A
authors.lastname: Dekkers
authors.affiliation: Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Mirjam
authors.initials: M
authors.lastname: Knol
authors.affiliation: NIVEL Primary Care Database, Sentinel Practices, Utrecht, The Netherlands.
authors.forename: Ge A
authors.initials: GA
authors.lastname: Donker
authors.affiliation: Department of Medical Microbiology, Academic Medical Center, Center for Infection and Immunity Amsterdam, Amsterdam, The Netherlands.|Netherlands Reference Laboratory for Bacterial Meningitis, Amsterdam, The Netherlands.
authors.forename: Arie
authors.initials: A
authors.lastname: van der Ende
authors.affiliation: Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Hester
authors.initials: H
authors.lastname: Korthals Altes
mesh_terms: D000293:Adolescent; D000368:Aged; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology / Q000821:virology; D005260:Female; D006801:Humans; D015994:Incidence; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D008297:Male; D008875:Middle Aged; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D012621:Seasons; D018571:Sentinel Surveillance; D062211:Spatio-Temporal Analysis; D013296:Streptococcus pneumoniae / Q000302:isolation & purification
keywords: 
  SARIMA
  ; cross-correlation; filtering; influenza; pneumococci; pre-whitening; respiratory tract infections