title: Post-infectious olfactory dysfunction exhibits a seasonal pattern.
abstract: OBJECTIVE
  We investigated whether olfactory dysfunction following infections of the upper respiratory tract (post-URTI) has an incidence matching the seasonality of URTIs.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  In total, 457 patients (126 male, 331 female) with post-URTI olfactory loss were examined during a 6-year-period (1999-2004). Their records were assessed for age, sex, and time of onset of the disease. The severity of olfactory dysfunction was assessed using the "Sniffin' Sticks" (odour threshold, odour discrimination, and odour identification).
  
  
  RESULTS
  Incidence of post-URTI olfactory dysfunction exhibited seasonal fluctuations with deviations from the winter seasonality of URTIs. The overall incidence of the disease differed significantly between months. March (12.7%) and May (12.6%) were the months with the highest incidence of the disease throughout the year. The lowest incidence was observed in September (5.6%). Significant differences were found between these months and months with a high incidence of URTIs.
  
  
  CONCLUSIONS
  The peak incidence of post-URTI olfactory loss in March may be explained by the high incidence of influenza at this time. However, it is unclear why the incidence of the disease presents a second peak in May, when the incidence of respiratory viruses is relatively low. Climate conditions at this time might play a role in the susceptibility of the nasal epithelia towards certain viral infections, e.g. parainfluenza type III.
  
  
  CONCLUSIONS
  Post-URTI olfactory dysfunction exhibits spring seasonality with peaks in March and May and possible causative factors being influenza and parainfluenza viruses (type III), respectively.
authors.affiliation: Smell & Taste Clinic, Department of Otorhinolaryngology, University of Dresden Medical School Technische Universität Dresden, Dresden, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Konstantinidis
authors.forename: A
authors.initials: A
authors.lastname: Haehner
authors.forename: J
authors.initials: J
authors.lastname: Frasnelli
authors.forename: J
authors.initials: J
authors.lastname: Reden
authors.forename: G
authors.initials: G
authors.lastname: Quante
authors.forename: M
authors.initials: M
authors.lastname: Damm
authors.forename: T
authors.initials: T
authors.lastname: Hummel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D000857:Olfaction Disorders / Q000453:epidemiology* / Q000209:etiology*; D012141:Respiratory Tract Infections / Q000150:complications*; D012189:Retrospective Studies; D012621:Seasons