Fungal aerobiology: how, when and where?

While there is undoubted risk of infection in certain hospitalized patients following exposure to inhaled spores of fungi such as Aspergillus, the actual risk appears to vary with the underlying condition. Secondly, the degree of exposure assessed by colony forming units (cfu) per unit of ambient air is not predictable. Thirdly, severely immunocompromised patients, mainly the severely neutropenic group, are at risk from infection at very low levels of ambient Aspergillus spores. From this it can be argued that the latter group requires some form of environmental protection or prophylaxis whatever the circumstances. At present the best approach is the use of highly filtered ward areas e.g. laminar air flow rooms. Monitoring spore loads is unlikely to affect management per se provided that the ventilation systems are regularly and effectively serviced. In non-neutropenic patients the risk of infection due to colonization, for instance of the paranasal sinuses, prior to hospital admission may be as great as that occurring due to exposure within hospital and filtration of air has a lesser value. The situation may alter, though, even in these patients if the risk level is increased by a building programme in the vicinity of ward areas.