ReviewNosocomial aspergillosis in outbreak settings
Introduction
Aspergillus spores are ubiquitous in their distribution, and inhalation of spores is believed to be the usual route of transmission. In most healthy individuals, spores are removed by functional innate defence mechanisms such as monocyte-derived and resident macrophages.1 Unfortunately, in severely immunocompromised hosts, such as patients suffering from haematological malignancies2, 3, 4, 5, 6 or solid organ transplant patients,7, 8, 9, 10, 11 invasive aspergillosis (IA) may represent a serious complication in the course of disease. The incidence of IA is increased in these high-risk patients12 with an overall case-fatality rate of one-half to two-thirds.13 IA is difficult to treat and multi-variate analysis has revealed it to be an independent risk factor for mortality in critically ill patients.14
To prevent hospital-acquired aspergillus infections, high-risk patients are usually placed in protective isolation rooms in which positive air pressure is maintained compared with surrounding areas.15 These special rooms are provided with high-efficiency particulate air (HEPA) filters and an air flow of at least 12 air changes/h because HEPA filtration significantly reduces the concentration of fungal spores16 and the incidence of IA.17 In addition, horizontal laminar air flow (LAF) is provided in some facilities which drives contaminants out through the ducts.18 However, additional protection due to LAF remains a matter of debate and the use of LAF is not explicitly recommended by the Centers for Disease Control and Prevention (CDC), the Infectious Disease Society of America (IDSA) or the American Society of Blood and Marrow Transplantation (ASBMT) for the care of haematopoietic stem cell transplant recipients.15, 19 Despite such guidelines for the care of highly susceptible patients and maximum protective efforts, nosocomial outbreaks of IA do occur.19, 20 This systematic review was carried out to summarize the data from all nosocomial aspergillus outbreak reports published to date.
Section snippets
Collection of data
The outbreak database (www.outbreak-database.com), a web-based register of nosocomial epidemics, was searched for outbreaks due to any type of Aspergillus spp.21 Furthermore, a PubMed search (1 January 1966–15 August 2005) was performed to identify additional aspergillus outbreaks by using the term ‘outbreak’ in combination with ‘aspergillus’ or ‘aspergillosis’. References were subsequently screened for additional descriptions of aspergillus epidemics in hospital settings.
Extraction of data
The following data
Results
A total of 53 outbreaks and 458 affected patients were included in this review. Comprising a total of 299 individuals (65.3%), haematological malignancies were the predominant underlying disease. In all but one outbreak, air was the route of fungal spore transmission and the major site of primary infection (356 patients) was the lower respiratory tract.22 Surgical site infections and superficial skin infections were observed far less frequently (24 patients each). Interpatient spread was only
Discussion
Today, construction in or around hospitals is a never-ending phenomenon. This review suggests that construction, renovation, demolition and excavation activities are the main causes of nosocomial aspergillus outbreaks. This is plausible because renovation and demolition work have been shown to increase the amount of airborne fungal spores dramatically,34 and in consequence increase the risk for aspergillus infection in susceptible patients.35 Routes of aspergillus transmission in nosocomial
References (92)
- et al.
Impact of air filtration on nosocomial aspergillus infections. Unique risk of bone marrow transplant recipients
Am J Med
(1987) - et al.
Incidence of invasive aspergillosis after allogeneic hematopoietic stem cell transplantation with a reduced-intensity regimen compared with transplantation with a conventional regimen
Biol Blood Marrow Transplant
(2004) - et al.
Fatal disseminated aspergillosis following sequential heart and stem cell transplantation for systemic amyloidosis
Am J Transplant
(2001) - et al.
Invasive aspergillosis in critically ill patients: attributable mortality and excesses in length of ICU stay and ventilator dependence
J Hosp Infect
(2004) Positive-pressure isolation and the prevention of invasive aspergillosis. What is the evidence?
J Hosp Infect
(2004)- et al.
Invasive aspergillosis in severely neutropenic patients over 18 years: impact of intranasal amphotericin B and HEPA filtration
J Hosp Infect
(1998) - et al.
Control of an outbreak of nosocomial aspergillosis by laminar air-flow isolation
J Hosp Infect
(1989) - et al.
Characterization of a possible nosocomial aspergillosis outbreak
Clin Microbiol Infect
(2000) - et al.
Environmental investigations and molecular typing of Aspergillus flavus during an outbreak of postoperative infections
J Hosp Infect
(2004) - et al.
Relationship between environmental fungal contamination and the incidence of invasive aspergillosis in haematology patients
J Hosp Infect
(2001)