ASPERGILLOSIS IS A RARE disease caused by the fungus aspergillus. The incidence of aspergillosis is difficult to determine because it isn't a reportable infection. More than 10,000 hospitalizations related to aspergillus infections are estimated to occur in the United States each year, resulting in more than 1,900 deaths.1 Defining healthcare-associated aspergillosis is challenging because its incubation period is unknown. However, fungal healthcare-associated infections have increased in the last few decades, and healthcare-associated aspergillus outbreaks are especially dangerous for immunocompromised patients and those with chronic pulmonary conditions such as cystic fibrosis and asthma.2 Mortality up to 60% has been reported with aspergillus infections in high-risk hematology patients.3
The Aspergillus species, which includes more than 150 types of mold, is widely distributed both indoors and outdoors. The air we breathe contains these fungal spores, but only certain types of aspergillus are associated with human disease.
The two most common causative agents in humans are Aspergillus fumigatus and Aspergillus flavus. Inhalation of these small fungal spores (2 to 3 microns) is believed to be the usual transmission route.4 People with healthy immune systems usually aren't harmed, but those with weakened immune systems can become seriously ill.
Presentation varies from an allergic reaction and mild infection in otherwise healthy individuals (allergic bronchopulmonary aspergillosis [ABPA]) to a serious lung infection called disseminated or invasive aspergillosis (IA) that can spread to the bloodstream, brain, heart, and kidneys. Aspergillus isn't contagious or spread person to person.
In a hospital setting, exposure can happen during building renovation or construction when dust containing fungal spores is released into the air. Research has shown that concentrations of aspergillus below one colony-forming unit/m3 are sufficient to cause infection in high-risk patients.5 Vehicles for spore transmission include improperly functioning ventilation systems, poorly maintained air filters, contamination of false ceilings and insulation material, water leaks, food, and ornamental plants. These spores may also contaminate biomedical devices, ventilators, monitors, surgical instruments, water supply systems, air conditioning ducts, and bedrails.6
The signs and symptoms of aspergillosis vary.7 Fever, hemoptysis, and shortness of breath are common in patients with ABPA. People with cystic fibrosis and asthma are most susceptible to ABPA; 1% to 2% of people with asthma and 10% to 15% of those with cystic fibrosis will develop APBA.8
Patients with emphysema and tuberculosis are more likely to develop a fungal mass known as pulmonary aspergilloma. Signs and symptoms include hemoptysis, wheezing, unintentional weight loss, and fatigue.1
The most severe form of aspergillosis is IA, which occurs when the infection spreads rapidly from the lungs to the bloodstream. Signs and symptoms include fever, cough, severe bleeding from the lungs, and epistaxis. Severely immunocompromised patients, such as those who've received bone marrow or solid organ transplants, are at the greatest risk for IA with an overall case mortality of one-half to two-thirds.5 Severity of signs and symptoms depends on the patient's clinical status and risk factors.
Diagnosis is a challenge because aspergillus is difficult to distinguish from other molds under a microscope. A chest X-ray or computed tomography scan can show a fungal mass, which is characteristic of IA and ABPA. A bronchoscopy or biopsy of tissue from the lungs or sinuses can also confirm IA, and a sputum Gram stain can detect aspergillus filaments. New nonculture-based serological assays and panfungal polymerase chain reaction assays have been developed for use with blood and other clinical specimens.3
First-line treatment for aspergillosis is the antifungal voriconazole, but other antifungals can be used for patients who can't take voriconazole or who haven't responded to it. These include itraconazole, posaconazole, lipid amphotericin formulations, caspofungin, and micafungin. Whenever possible, discontinue or decrease immunosuppressive medications in these patients.9
Preventing the spread
Aspergillus infections are costly for healthcare facilities. In the United States, mean total hospital costs of IA have been estimated at $96,310.3 The CDC and the Healthcare Infection Control Practices Advisory Committee provide recommendations for environmental infection control measures in healthcare facilities. These include infection control strategies and engineering controls directed primarily at the prevention of exposure of immunocompromised patients to environmental airborne fungal spores of aspergillus and other molds.2
Robust surveillance programs during hospital construction that monitor air quality and ventilation should be initiated with input from the hospital's infection prevention practitioner and engineering services. Controlling airborne pathogens through strict quality control procedures, such as use of high efficiency particulate air filters with 99.97% efficiency, is critical to contain these microorganisms.10 Deliberate placement or cohorting of high-risk patients into safe environments is essential.
Immunocompromised patients should wear filtration masks when in or near construction sites and avoid activities that involve contact with soil, such as gardening and yard work. They can also reduce their risk of exposure by using HEPA filters in their home and cleaning skin injuries thoroughly with soap and water.11
2. Alangaden GJ. Nosocomial fungal infections: epidemiology, infection control, and prevention. Infect Dis Clin North Am
3. Morrissey CO. Advancing the field: evidence for new management strategies in invasive fungal infections. Curr Fungal Infect Rep
5. Vonberg RP, Gastmeier P. Nosocomial aspergillosis in outbreak settings. J Hosp Infect
10. Rangaswamy BE, Francis F, Prakash KK, Manjunath NS. Variability in airborne bacterial and fungal population in the tertiary health care centre. Aerobiologia