title: An outbreak of influenza A(H3N2) in Alappuzha district, Kerala, India, in 2011.
abstract: BACKGROUND
  Influenza is an RNA virus that belongs to the Orthomyxoviridae family. It causes a highly contagious acute respiratory illness, has been recognized since ancient times, and is a major health threat throughout the world. An outbreak of influenza-like illness (ILI) was reported from Alappuzha district of Kerala State between late June and July 2011. This investigation was conducted to determine the clinical picture, causative agents, and epidemiological characteristics of the illness.
  
  
  METHODS
  The World Health Organization (WHO)'s case definition for ILI was followed throughout the investigation. Nasal or throat swabs were collected from 204 suspected patients. Real-time reverse transcription polymerase chain reaction (RT-PCR)-based diagnosis was performed to detect influenza A and B viruses and their subtypes. Madin-Darby canine kidney (MDCK) cell line was used for virus isolation. One-step RT-PCR was performed to amplify the HA1 gene of influenza A(H3N2). The amplicons for the HA1 gene of influenza A(H3N2) were sequenced, and phylogenetic analysis was done.
  
  
  RESULTS
  Analysis of the data revealed that 96 (47.05%) of the 204 respiratory specimens collected were influenza A(H3N2) and only 6 (2.94%) were A(H1N1)pdm09. Phylogenetic analysis revealed that the isolated A(H3N2) was closely related to the 2012-2013 northern hemisphere vaccine strain (A/Victoria/361/2011/H3N2).
  
  
  CONCLUSIONS
  An influenza A(H3N2) outbreak was confirmed in Alappuzha district of Kerala state with a co-circulation of A(H1N1)pdm09. No substantial difference in the sequence was observed in the etiological agent, and the virus was found to be sensitive to oseltamivir.
authors.affiliation: National Institute of Virology (NIV), Kerala Unit, Medical College Hospital Complex, Alappuzha, Kerala, India. sampallikaparampil@gmail.com.
authors.forename: Sam
authors.initials: S
authors.lastname: Peter
authors.forename: Anukumar
authors.initials: A
authors.lastname: Balakrishnan
authors.forename: Varsha A
authors.initials: VA
authors.lastname: Potdar
authors.forename: Mandeep S
authors.initials: MS
authors.lastname: Chadha
authors.forename: Santhosh M
authors.initials: SM
authors.lastname: Jadhav
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D005838:Genotype; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D007194:India / Q000453:epidemiology; D007223:Infant; D053122:Influenza A Virus, H3N2 Subtype / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology / Q000821:virology*; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D009297:Nasal Mucosa / Q000821:virology; D009975:Orthomyxoviridae; D010614:Pharynx / Q000821:virology; D010802:Phylogeny; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014776:Virus Cultivation; D055815:Young Adult
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus