Counterpoint: invasive aspergillosis and the environment--rethinking our approach to prevention.

Preventive measures are important in the control of invasive aspergillosis (IA) because diagnosis is difficult and the outcome of treatment is poor. If effective strategies are to be devised, it will be essential to have a clearer understanding of the sources and routes of transmission of Aspergillus species. Nosocomial outbreaks of IA highlight the fact that Aspergillus spores are common in the hospital environment. However, in general, such outbreaks are uncommon. Most cases of IA are sporadic in nature, and many of them are now being acquired outside of the hospital setting. Housing patients in high-energy particulate air-filtered hospital rooms helps prevent IA, but it is feasible and cost-effective only for the highest-risk groups and for limited periods. Control measures, which are designed to protect patients from exposure to spores outside the hospital, are even more difficult. Nevertheless, now that high-risk patients are spending more time outside of the hospital, the cost benefits of antifungal prophylaxis and other preventive measures require careful evaluation.