title: Symptoms in the host: infection and treatment model.
abstract: OBJECTIVE
  The aim is to devise a decision-making model to help nurses and allied professionals treat the symptoms of infectious diseases in a logical way that maximizes the benefits of symptoms and minimizes any harm that they might do.
  
  
  BACKGROUND
  This paper considers the symptoms of infectious diseases from an evolutionary perspective, applying theories from ecology and evolution to nursing. Building upon evolutionary theories that suggest symptoms occur as the result of host defences, pathogen manipulations or as pure side-effects, it is suggested that those symptoms that have evolved as host defences should not always be treated because of their beneficial effects. However, clinical decision-making is more complex because of the rapid changes in environment and behaviour, which may impact upon the usefulness of symptoms to the host.
  
  
  CONCLUSIONS
  Although some symptoms can be identified as being beneficial adaptations, this alone is not sufficient indication to decide which symptoms should or should not be treated. Other considerations include any negative outcomes and behavioural and environmental changes that may affect the significance of any adaptation.
  
  
  CONCLUSIONS
  Nurses should aim to maximize the host defences of the patients they are caring for in order to speed recovery and to reduce transmission and the need for antibiotics. This model helps nurses to identify factors that should be considered when these decisions are made and suggests some principles that might be followed in other situations.
authors.affiliation: King's College London, London, UK. edward.purssell@kcl.ac.uk
authors.forename: Edward
authors.initials: E
authors.lastname: Purssell
mesh_terms: D000222:Adaptation, Physiological; D005075:Biological Evolution; D015984:Causality; D003141:Communicable Diseases / Q000382:microbiology / Q000628:therapy / Q000635:transmission; D003371:Cough / Q000382:microbiology; D003661:Decision Support Techniques; D003967:Diarrhea / Q000382:microbiology; D005334:Fever / Q000382:microbiology; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology*; D010146:Pain / Q000382:microbiology; D018579:Patient Selection