title: Emergence of 2009A/H1N1 cases in a tertiary care hospital in New Delhi, India.
abstract: OBJECTIVE
  To determine virologic and epidemiologic characteristics of pandemic (H1N1) 2009 at All India Institute of Medical Sciences (AIIMS) a tertiary care hospital in New Delhi, India.
  
  
  METHODS
  Nasal and throat swabs from patients with febrile acute respiratory illness (FARI) from August to December 2009 (n = 1401) were tested for 2009A/H1N1 and seasonal influenza A viruses by real-time RT-PCR.
  
  
  RESULTS
  Of 1401 samples tested, 475 (33·9%) were positive for influenza A, of these majority (412; 87%) were 2009A/H1N1, whereas the remaining 63 (13%) were seasonal influenza A (49 were A/H3 and 14 were A/H1). While co-circulation of 2009A/H1N1 and A/H3 was observed in August-September, subsequent months had exclusive pandemic influenza activity (October-December 2009). Pandemic 2009A/H1N1 emergence did not follow typical seasonal influenza seasonality in New Delhi, which normally peaks in July-August, but instead showed bimodal peaks in weeks 39 and 48 in 2009. The percent of specimens testing positive for 2009A/H1N1 influenza virus was found to be highest in >5- to 18-year age group (41·2%; OR = 2·3; CI = 1·6-3·2; P = 0·00).
  
  
  CONCLUSIONS
  Taken together, our data provide high prevalence of pandemic 2009A/H1N1 in urban New Delhi with bimodal peaks in weeks 39 and 48 and highest risk group being the children of school-going age (aged >5-18).
authors.affiliation: Department of Microbiology, All India Institute of Medical Sciences, New Delhi, India. shobha.broor@gmail.com
authors.forename: Shobha
authors.initials: S
authors.lastname: Broor
authors.forename: Swati
authors.initials: S
authors.lastname: Gupta
authors.forename: Sarita
authors.initials: S
authors.lastname: Mohapatra
authors.forename: Samander
authors.initials: S
authors.lastname: Kaushik
authors.forename: Muneer A
authors.initials: MA
authors.lastname: Mir
authors.forename: Priti
authors.initials: P
authors.lastname: Jain
authors.forename: Lalit
authors.initials: L
authors.lastname: Dar
authors.forename: Renu B
authors.initials: RB
authors.lastname: Lal
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D005260:Female; D006760:Hospitalization; D006761:Hospitals; D006801:Humans; D007194:India / Q000453:epidemiology; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D009980:Influenza A virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D008297:Male; D008875:Middle Aged; D012621:Seasons; D055815:Young Adult