title: Laboratory-Enhanced Dengue Sentinel Surveillance in Colombo District, Sri Lanka: 2012-2014.
abstract: BACKGROUND
  Dengue has emerged as a significant public health problem in Sri Lanka. Historically surveillance was passive, with mandatory dengue notifications based on clinical diagnosis with only limited laboratory confirmation. To obtain more accurate data on the disease burden of dengue, we set up a laboratory-based enhanced sentinel surveillance system in Colombo District. Here we describe the study design and report our findings of enhanced surveillance in the years 2012-2014.
  
  
  METHODS
  Three outpatient clinics and three government hospitals in Colombo District that covered most of the Colombo metropolitan area were selected for the sentinel surveillance system. Up to 60 patients per week presenting with an undifferentiated fever were enrolled. Acute blood samples from each patient were tested by dengue specific PCR, NS1 ELISA and IgM ELISA. A sub-set of samples was sent to Duke-NUS Singapore for quality assurance, virus isolation and serotyping. Trained medical research assistants used a standardized case report form to record clinical and epidemiological data. Clinical diagnoses by the clinicians-in-charge were recorded for hospitalized cases.
  
  
  RESULTS
  Of 3,127 febrile cases, 43.6% were PCR and/or NS1 positive for dengue. A high proportion of lab confirmed dengue was observed from inpatients (IPD) (53.9%) compared to outpatient (clinics in hospitals and general practice) (7.6%). Dengue hemorrhagic fever (DHF) was diagnosed in 11% of patients at the time of first contact, and the median day of illness at time of presentation to the sentinel sites was 4. Dengue serotype 1 was responsible for 85% of the cases and serotype 4 for 15%. The sensitivity and specificity of the clinicians' presumptive diagnosis of dengue was 84% and 34%, respectively.
  
  
  CONCLUSIONS
  DENV-1, and to a lesser degree DENV-4, infection were responsible for a high proportion of febrile illnesses in Colombo in the years 2012 to 2014. Clinicians' diagnoses were associated with high sensitivity, but laboratory confirmation is required to enhance specificity.
authors.affiliation: Epidemiology Unit, Ministry of Health, Colombo, Sri Lanka.|National Dengue Control Unit, Colombo, Sri Lanka.
authors.forename: Hasitha
authors.initials: H
authors.lastname: Tissera
authors.affiliation: Epidemiology Unit, Ministry of Health, Colombo, Sri Lanka.
authors.forename: Ananda
authors.initials: A
authors.lastname: Amarasinghe
authors.affiliation: Medical Research Institute, Colombo, Sri Lanka.
authors.forename: Sunethra
authors.initials: S
authors.lastname: Gunasena
authors.affiliation: Genetech Research Institute, Colombo, Sri Lanka.
authors.forename: Aruna Dharshan
authors.initials: AD
authors.lastname: DeSilva
authors.affiliation: Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.
authors.forename: Leong Wei
authors.initials: LW
authors.lastname: Yee
authors.affiliation: Program in Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore.
authors.forename: October
authors.initials: O
authors.lastname: Sessions
authors.affiliation: Epidemiology Unit, Ministry of Health, Colombo, Sri Lanka.
authors.forename: Chanaka
authors.initials: C
authors.lastname: Muthukuda
authors.affiliation: Epidemiology Unit, Ministry of Health, Colombo, Sri Lanka.
authors.forename: Paba
authors.initials: P
authors.lastname: Palihawadana
authors.affiliation: Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University, Umeå, Sweden.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lohr
authors.affiliation: Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University, Umeå, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Byass
authors.affiliation: Program in Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Duane J
authors.initials: DJ
authors.lastname: Gubler
authors.affiliation: Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.|Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University, Umeå, Sweden.
authors.forename: Annelies
authors.initials: A
authors.lastname: Wilder-Smith
mesh_terms: D064790:Clinical Laboratory Services; D003715:Dengue / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D003716:Dengue Virus / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D003955:Diagnostic Tests, Routine / Q000379:methods*; D006801:Humans; D007755:Laboratories, Hospital; D012680:Sensitivity and Specificity; D018571:Sentinel Surveillance; D013188:Sri Lanka / Q000453:epidemiology