Invasive aspergillosis presents a formidable problem for both diagnosis and therapy. Therefore, prevention is a very important strategy in controlling this disease. Currently, the environmental mycology of most cases of invasive aspergillosis is poorly defined. However, the development of molecular techniques more directly applicable to
Aspergillus spp. may help resolve some of these difficulties. Preventing invasive aspergillosis demands a clear understanding of the environmental sources of
Aspergillus spp. and how this mould is transmitted to patients before, during and after hospitalization for transplantation. Exposure to
Aspergillus in hospital, especially during heavy construction or demolition, has been well documented. There appears to be a strong correlation between outbreaks of invasive aspergillosis and hospital building work. However, prevention of aspergillosis is relatively difficult. The HEPA filter appears to be the only effective means of decreasing the incidence of aspergillus infection. The principles of environmental control of nosocomial aspergillosis are complex given that even HEPA units are not completely effective in preventing disease. Alternatively, a systematic program of longitudinal patient and environmental surveillance may predict cases of invasive aspergillosis. Indeed, there appears to be a correlation between the recovery of
Aspergillus spp. from the nose and mouth of patients in an open hematology ward and an elevated number of conidia in the air. The relationship between aspergillosis in predisposed patients and building work is also complex. Whether or not this activity is complicated by an outbreak of infection in the susceptible patients nearby, or is a risk related directly to the amount of disruption or some other factor, is unknown.
Aspergillus spp. have a major reservoir in organic debris, dust and building material. Susceptible patients should not be treated in areas where there is construction or demolition activity. Although outbreaks of invasive aspergillosis have been associated with construction within or around a hospital, the precise source of the fungus is very difficult to trace. New data suggest that patients may be exposed to
Aspergillus conidia in water supplies in hospitals and as a result of showering in patient bedroom facilities. Increasingly, cases of aspergillosis are being reported many months after transplantation and discharge from hospital. This scenario raises the question of community acquired disease following exposure to
Aspergillus in the home, the workplace or the outdoor. Returning to work after transplantation is a much-discussed topic today. Returning to work should not endanger their health. This means that occupational risks such as occupational exposure to
Aspergillus spores must be evaluated. The necessity of immunosuppressive therapy or the treatment for chronic graft versus host disease after transplantation elevates the aspergillosis risk, especially 1-6 months after transplantation. The risk of acquiring aspergillosis at work exists, but is not easily quantifiable. Nevertheless, the risk should be minimized during the period of vulnerability by preventive measures such as restriction of certain activities, changing work methods and reorganizing the work day to adapt to the risk, and wearing personal protective equipment, as well as attention to information about aspergillosis risk and about the likelihood of exposure in the patient's professional and leisure activities. From an epidemiological point of view, molecular study of moulds either isolated from patients or the environment will increase our understanding of the acquisition and route of infection. Various molecular techniques are available to genotype moulds. Discriminative typing methods are now available.
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