title: Prospective study of the incidence, aetiology and outcome of adult lower respiratory tract illness in the community.
abstract: BACKGROUND
  Acute lower respiratory tract illness in previously well adults is usually labelled as acute bronchitis and treated with antibiotics without establishing the aetiology. Viral infection is thought to be the cause in most cases. We have investigated the incidence, aetiology, and outcome of this condition.
  
  
  METHODS
  Previously well adults from a stable suburban population consulting over one year with a lower respiratory tract illness were studied. For the first six months detailed investigations identified predetermined direct and indirect markers of infection. Evidence of infection was assessed in relation to presenting clinical features, indirect markers of infection, antibiotic use, and outcome.
  
  
  RESULTS
  Consultations were very common, particularly in younger women (70/1000 per year in previously well women aged 16-39 years), mainly in the winter months; 638 patients consulted, of whom 316 were investigated. Pathogens were identified in 173 (55%) cases: bacteria in 82 (Streptococcus pneumoniae 54, Haemophilus influenzae 31, Moraxella catarrhalis 7), atypical organisms in 75 (Chlamydia pneumoniae 55, Mycoplasma pneumoniae 23), and viruses in 61 (influenza 23). Seventy nine (24%) had indirect evidence of infection. Bacterial and atypical infection correlated with changes in the chest radiograph and high levels of C reactive protein but not with (a) the GP's clinical assessment of whether infection was present, (b) clinical features other than focal chest signs, and (c) outcome, whether or not appropriate antibiotics were prescribed.
  
  
  CONCLUSIONS
  Over 50% of patients have direct and/or indirect evidence of infection, most commonly bacterial and atypical pathogens, but the outcome is unrelated to the identified pathogens. Many patients improve without antibiotics and investigations do not help in the management of these patients. GPs can reassure patients of the causes and usual outcome of this self-limiting condition.
authors.affiliation: Respiratory Infection Group, Nottingham City Hospital, Nottingham NG5 1PB, UK. john.macfarlane@nottingham.ac.uk
authors.forename: J
authors.initials: J
authors.lastname: Macfarlane
authors.forename: W
authors.initials: W
authors.lastname: Holmes
authors.forename: P
authors.initials: P
authors.lastname: Gard
authors.forename: R
authors.initials: R
authors.lastname: Macfarlane
authors.forename: D
authors.initials: D
authors.lastname: Rose
authors.forename: V
authors.initials: V
authors.lastname: Weston
authors.forename: M
authors.initials: M
authors.lastname: Leinonen
authors.forename: P
authors.initials: P
authors.lastname: Saikku
authors.forename: S
authors.initials: S
authors.lastname: Myint
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001991:Bronchitis / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology; D023521:Chlamydophila Infections / Q000453:epidemiology; D017714:Community-Acquired Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology; D005260:Female; D006192:Haemophilus Infections / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016870:Neisseriaceae Infections / Q000453:epidemiology; D011008:Pneumococcal Infections / Q000453:epidemiology; D018410:Pneumonia, Bacterial / Q000453:epidemiology; D011019:Pneumonia, Mycoplasma / Q000453:epidemiology; D011446:Prospective Studies; D012621:Seasons; D016896:Treatment Outcome; D014777:Virus Diseases / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents