title: Reducing occurrence and severity of pneumonia due to pandemic H1N1 2009 by early oseltamivir administration: a retrospective study in Mexico.
abstract: BACKGROUND
  Anti-viral treatment has been used to treat severe or progressive illness due to pandemic H1N1 2009. A main cause of severe illness in pandemic H1N1 2009 is viral pneumonia; however, it is unclear how effective antiviral treatment is against pneumonia when administered >48 hours after symptom onset. Therefore, we aimed to determine how time from symptom onset to antiviral administration affected the effectiveness of antiviral treatment against pneumonia due to pandemic (H1N1) 2009.
  
  
  RESULTS
  A retrospective medical chart review of 442 patients was conducted in a hospital in Mexico. Subjects had tested positive for pandemic H1N1 2009 virus by real-time reverse-transcriptase-polymerase-chain-reaction and were administered oseltamivir. Median time from symptom onset to oseltamivir administration was 5.0 days (range, 0-43). 442 subjects, 71 (16.1%) had severe pneumonia which required mechanical ventilation, 191 (43.2%) had mild to moderate pneumonia, and 180 (40%) did not have pneumonia. Subjects were divided into four groups based on time to oseltamivir administration: ≤2, 3-7, 8-14, and >14 days. Severity of respiratory features was associated with time to treatment, and multivariate analysis indicated that time to oseltamivir administration was associated with severity of respiratory features. A proportional odds model indicated that 50% probability for occurrence of pneumonia of any severity and that of severe pneumonia in patients who would develop pneumonia reached at approximately 3.4 and 21 days, respectively, after symptom onset. Patients with a shorter time to oseltamivir administration were discharged earlier from the hospital.
  
  
  CONCLUSIONS
  Earlier initiation of oseltamivir administration after symptom onset significantly reduced occurrence and severity of pneumonia and shortened hospitalization due to pandemic H1N1 2009. Even when administered >48 hours after symptom onset, oseltamivir showed considerable potential for reducing pneumonia. Application of these results would benefit patients affected by future influenza pandemics.
authors.affiliation: National Institute for Respiratory Disease, Mexico City, Mexico.
authors.forename: Anjarath Lorena
authors.initials: AL
authors.lastname: Higuera Iglesias
authors.forename: Koichiro
authors.initials: K
authors.lastname: Kudo
authors.forename: Toshie
authors.initials: T
authors.lastname: Manabe
authors.forename: Alexander Enrique
authors.initials: AE
authors.lastname: Corcho Berdugo
authors.forename: Ariel
authors.initials: A
authors.lastname: Corrales Baeza
authors.forename: Leticia
authors.initials: L
authors.lastname: Alfaro Ramos
authors.forename: René
authors.initials: R
authors.lastname: Guevara Gutiérrez
authors.forename: María Eugenia
authors.initials: ME
authors.lastname: Manjarrez Zavala
authors.forename: Jin
authors.initials: J
authors.lastname: Takasaki
authors.forename: Shinyu
authors.initials: S
authors.lastname: Izumi
authors.forename: Edgar
authors.initials: E
authors.lastname: Bautista
authors.forename: José Rogelio
authors.initials: JR
authors.lastname: Perez Padilla
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects / Q000502:physiology*; D007251:Influenza, Human / Q000150:complications / Q000188:drug therapy / Q000453:epidemiology / Q000821:virology*; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D015999:Multivariate Analysis; D053139:Oseltamivir / Q000008:administration & dosage* / Q000494:pharmacology / Q000627:therapeutic use*; D058873:Pandemics; D010343:Patient Admission; D010351:Patient Discharge; D011024:Pneumonia, Viral / Q000188:drug therapy* / Q000453:epidemiology / Q000517:prevention & control / Q000821:virology; D011336:Probability; D012189:Retrospective Studies; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D053139:Oseltamivir