Legionnaires' disease outbreak investigation toolbox

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Background immunity/antibody level in population

Collins [1; 2] examined human and various animal populations for the prevalence of Legionella- specific antibodies. They found that in the 286 human sera that they examined, 99.6% tested negative; suggesting that humans are rarely infected by Legionella, or that protection wanes and so most of the population are likely to have little or no pre-existing acquired-immunity against Legionnaires' disease. However Wedege el al [3] have found raised antibody levels in a population up to one year after an outbreak. It is very unlikely, therefore, that pre-existing acquired-immunity will affect the observed probability of infection, the duration of the incubation period, or indeed the dose-dependency of these two variables. There are, however, other less well quantitatively characterised factors related to, for example, innate immunity, aging and smoking, that probably are risk factors for the development of Legionnaires' disease.

Reference List

  1. COLLINS M. T., CHO S. N. & REIF J. S. (1982) Prevalence of antibodies to Legionella pneumophila in animal populations Journal of Clinical Microbiology 15, pp. 130 - 136 http
  2. COLLINS M.T. (1986) Legionella Infections in animals Israel Journal of Medical Sciences 22, pp.662 - 673 http
  3. WEDEGE E., BERGDAL T., BOLSTAD K., CAUGANT D. A., EFSKIND C. J., HEIER H. E., KANESTROM A., STRAND B. H. & AABERAGE I. S. (2009) Seroepidemiological study after a long-distance industrial outbreak of Legionnaires' disease Clinical and Vaccine Immunology 16, pp.528 - 534 http pdf