title: Co-circulations of two genotypes of dengue virus in 2006 out-break of dengue hemorrhagic fever in Karachi, Pakistan.
abstract: BACKGROUND
  The status of dengue genotypes involved in the recent epidemic out-breaks in Pakistan is not well defined.
  
  
  OBJECTIVE
  We sought to analyze the predominant genotype responsible for the most severe and largest out-break of dengue hemorrhagic fever (DHF) that hit Karachi in 2006.
  
  
  METHODS
  Retrospective analysis of stored serum samples for dengue virus genotype by multiplex RT-PCR, anti-dengue IgM, IgG and review of clinical charts of patients admitted to Aga Khan University Hospital.
  
  
  RESULTS
  Viral RNA detection of 250 patients revealed positive results in 185 (74.0%) samples. DEN-2 was predominant genotype (n=104, 56.2%) Dengue specific antibodies were detected in 139 samples of which 81 were classified as primary cases. DEN-2 accounted for these. Within secondary cases, 63.2% were due to DEN-2 (total 57), the rest were positive for DEN-3. DHF (p=0.064) and abdominal pain (p=0.059) were more frequently associated with DEN-2 as compared to DEN-3. None of the samples were positive for DEN-1 or DEN-4.
  
  
  CONCLUSIONS
  Co-circulation of DEN-2 and DEN-3 was responsible for the 2006 out-break in Karachi. Primary and secondary cases were seen in both groups. Cases with DHF showed marginal association with DEN-2. Introduction of a new serotype (DEN-3) and or a genotypic shift of endemic serotype (DEN-2) are the probable factors for the recent out-break of DHF in this region.
authors.affiliation: Department of Pathology & Microbiology, The Aga Khan University Hospital, Stadium Road, P.O. Box 3500, Karachi 74800, Pakistan. erum.khan@aku.edu
authors.forename: E
authors.initials: E
authors.lastname: Khan
authors.forename: R
authors.initials: R
authors.lastname: Hasan
authors.forename: V
authors.initials: V
authors.lastname: Mehraj
authors.forename: A
authors.initials: A
authors.lastname: Nasir
authors.forename: J
authors.initials: J
authors.lastname: Siddiqui
authors.forename: R
authors.initials: R
authors.lastname: Hewson
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D003716:Dengue Virus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D004196:Disease Outbreaks; D005260:Female; D005838:Genotype; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008875:Middle Aged; D010154:Pakistan / Q000453:epidemiology; D012367:RNA, Viral / Q000097:blood; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019595:Severe Dengue / Q000453:epidemiology* / Q000821:virology*; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012367:RNA, Viral