Respiratory Infections

Rhinoviruses and coronaviruses are among the most prevalent upper respiratory tract pathogens and exist in too many serotypes to make serological diagnosis possible. The common cold therefore remains a clinical diagnosis.
Lower respiratory tract infections cause a high degree of morbidity and mortality and traditional culture or serological methods often fail or take a long time. Real-time PCR and other nucleic amplification techniques have great potential for rapid and exact diagnosis. The main limitation currently is the cost compared with cheaper serological diagnoses such as the complement fixation test. In selected cases, nucleic acid extraction from expectorate followed by amplification in order to detect Chlamydia pneumoniae, Mycoplasma pneumoniae, Bordetella pertussis, Legionella pneumophila34–38 or Mycobacterium tuberculosis is most valuable. In children hospitalised with breathing difficulties due to bronchiolitis, reverse PCR tests for metapneumovirus and RSV complement the rapid immunofluorescent diagnosis available for a number of viruses in nasopharyngeal aspirates (influenza A and B viruses, parainfluenza viruses, adenovirus and RSV). In the initial stage of new influenza epidemics, real-time PCR assays to identify and type influenza A and B viruses are replacing viral isolation as the reference standard. Real-time PCR assays are available for the emergency analysis of avian influenza H5N1 and also for the SARS virus.