Preventing Aspergillus Infection during Hospital Construction Work
What is Aspergillus and why is it a hazard for certain hospitalised patients?
Aspergillus is an environmental mould fungus that survives in soil and dust. Disturbance of these during hospital building, renovation or demolition work can generate airborne spores of the fungus which if inhaled by susceptible patients can lead to an often fatal lung infection called invasive aspergillosis.
Which patients are at risk of developing invasive aspergillosis?
Severely immunocompromised patients such as those undergoing treatment for leukaemia, transplant recipients or those receiving long-term immunosuppressive therapies, e.g. steroids, are at risk of developing invasive aspergillosis.
Patients in intensive care, particularly those with underlying chronic lung conditions e.g. Chronic Obstructive Pulmonary Disease (COPD) have more recently been identified as being at increased risk. On the basis of the known incidence of invasive aspergillosis in these patient populations an at-risk classification can be devised which guides the preventive measures needed for their protection during hospital building work.
What preventive measures are effective to prevent nosocomial aspergillosis?
A risk assessment will help to devise a combination of measures that may include environmental dust control and cleaning, prevention of ingress of airborne spores from outside clinical areas, protective environments for highest risk patients, and antifungal drug prophylaxis.
What type(s) of protective environment are used to prevent nosocomial aspergillosis?
HEPA-filtered positive pressure isolation rooms are the only type of protective environment for which there is a scientific evidence base. Recently, neutral pressure isolation rooms have been introduced which may provide some protection to at-risk patients but they have not been shown to reliably prevent ingress of fungal spores from outside the patient’s isolation room.
Which antifungal drugs are effective for prophylaxis against Aspergillus infection, and which patients should be prescribed them?
Published international guidelines show that the evidence for effective prevention of Aspergillus infection is limited to patients with haematological malignancies and those undergoing haematopoietic stem cell transplantation. The triazole Posaconazole has the strongest grade of recommendation in these groups.
Is there concern about triazole antifungal drug resistance in Aspergillus?
Resistance to the triazoles in the main pathogenic species Aspergillus fumigatus has been reported in an increasing number of countries. To date, the prevalence of drug resistance is variable and unpredictable. Ideally all clinical isolates of A. fumigatus from at-risk patients should be tested in vitro for susceptibility to triazoles. Other Aspergillus species are less commonly identified as pathogens in this setting but have less predictable susceptibility to triazoles.
Should clinical areas with at-risk patients be monitored by environmental air sampling?
Routine air sampling is not recommended; however, where major works are to be undertaken it may be useful to establish baseline levels of Aspergillus in the air and continue to monitor during construction work in order to detect increased counts which will prompt additional preventive measures.
Is aspergillosis difficult to diagnose?
Yes, because clinical symptoms and signs are not specific to invasive aspergillosis and a definitive diagnosis by e.g. lung tissue biopsy is often not feasible. A combination of clinical, radiological, and laboratory criteria help to identify patients with probable invasive aspergillosis. These measures should be employed as part of monitoring at-risk patients during any construction activities.
Do all patients who develop evidence of invasive aspergillosis acquire it from the hospital environment?
No, some patients may be admitted to hospital with Aspergillus infection that is not clinically manifested but only when they receive intensive immunosuppression do they develop clinical signs and symptoms.
What measures should be taken before a hospital project associated with potential release of airborne Aspergillus spores is started?
All interested parties must be informed in advance of the scope and activity of the planned project. The Hospital Infection Prevention and Control Team will advise on which clinical areas with at-risk patients may become affected and what appropriate preventive measures are required. Tender documents must comply with national and local guidelines on prevention of nosocomial aspergillosis. A permit to work will be required for each phase of the project.
Last reviewed: January 2018