EDCP Mission/Vision

March, 1999

Clinical Syndromes
Prevention and Control Measures
References

Introduction

Aspergilli are a group of fungi ubiquitous in nature and easily cultured from air, water, soil, vegetation, and any site where dust accumulates. In appropriate conditions the organism forms large amounts of spores which are released into the environment where they may remain suspended for long periods. Aspergillus spores are small (2.5 to 3.5 microns in diameter) and easily inhaled where they may colonize the upper or lower airways. Several hundred species of Aspergillus exist with two causing the majority of disease in humans, A fumigatus and A. flavus.

In highly immunocompromized hosts Aspergillus spp. causes severe opportunistic infections that carry a high mortality. Although invasive aspergillosis may be community acquired, most cases are nosocomial in origin. Major outbreaks of invasive nosocomial aspergillosis have been reported associated with hospital construction, renovation and maintenance, activities that allow spores to become airborne.

Clinical Syndrome

Prevention and Control Measures

1. Define patients at risk

Certain categories of patients are at increased risk for development of nosocomial pulmonary aspergillosis. Identification of these patients at time of admission is important so that they can be protected from dangerous exposure to aspergillus spores. These categories include:

• Patients with severe and prolonged granulocytopenia defined as 1,000 polymorphonuclear cells\mm3 for 2 weeks or 100 polymorphonuclear cells\mm3 for 1 week.
• Those receiving immunosuppressive therapy such as that given during bone marrow and solid organ transplantation. This includes patients who are neutropenic due to leukemia, lymphoma, aplastic anemia and other myeloplastic diseases.
• Those with congenital or acquired immunodeficiency syndrome.
• Those who are immunocompromised due to extreme prematurity, or severe underlying illness.
• Patients undergoing prolonged, high dose corticosteroid treatment such as that given to rheumatology patients.

2. Establish a case definition for active surveillance of cases of pulmonary aspergillosis

Diagnosis of invasive pulmonary aspergillosis is difficult. Isolation of Aspergillus spp. from respiratory secretions alone is not diagnostic but may merely indicate colonization. Additionally, patients with invasive disease may have negative cultures. Blood cultures are unreliable. Definitive diagnosis of invasive aspergillosis usually requires biopsy of the involved tissue. It is important to consider the clinical picture when searching for cases. For example, in a granulocytopenic patient with fever, a new pulmonary infiltrate, and Aspergillus spp. in the sputum, pulmonary aspergillosis is likely.

Confirmed case: Any patient with histopathlogic evidence of invasive disease (e.g., fungal invasion seen in tissue biopsy).

Probable case: Any patient with Aspergillus spp. isolated by culture and clinical signs and symptoms compatible with pulmonary aspergillosis.

Colonized case: Any patient with Aspergillus spp. isolated by culture and no clinical evidence of fungal infection.

• Maintain a high index of suspicion for the diagnosis of nosocomial pulmonary aspergillosis in high-risk patients
• Systematically review the hospital�s microbiologic, histopathologic, and post mortem data to search for cases.
• Notify physicians to report cases if there is suspicion of the diagnosis of nosocomial aspergillosis for patients at risk.

4. When admitting high-risk patients to the hospital

• Admit patients at risk to rooms in which the incoming air is filtered with a high efficiency particulate air (HEPA) filter.
• Ensure that room-air pressure can be kept continuously above that of the hallway.
• Maintain room air-changes>=12 air changes per hour.
• Ensure that the windows are well sealed against air leaks in high-risk patients� rooms.
• While immunocompromised, minimize the time these patients spend outside their rooms and consider requiring patients to wear well-fitting masks capable of filtering Aspergillus spp. spores.
• Assign these patients to rooms removed from or physically separated from construction activity.

6. Prevention and control measures prior to and during construction or renovation activities

The major extrinsic risk factor for opportunistic, invasive Aspergillus infection is the presence of aspergilli in the hospital environment, especially from environmental disturbances during construction or renovation. It is particularly important that prior to starting any construction project that the Facilities Department consult with and coordinate activities with the Hospital Infection Control Department to minimize the generation and movement of dust into high-risk patient areas.

• Relocation of high-risk patients to unaffected areas before construction work begins may be necessary.
• Isolate construction sites and create impermeable barriers (e.g., plastic) between patient-care and construction areas.
• Direct pedestrian traffic from construction areas away from patient-care areas to prevent any dust dispersion, entry of contaminated air, or tracking of dust into patient areas.
• Maintain constant negative air pressure in construction areas relative to patient-care areas.
• Remove air from the construction site by venting it directly to the outside. When this is not possible, high-efficiency particulate air (HEPA) filters must be used on the air before returning it to the ventilation system.
• All air-handling ducts should be shut down or covered during all demolition activities.
• Thoroughly clean new and renovated wards before admitting patients in these areas.

7. If one or more cases of nosocomial aspergillosis occurs

• Intensify surveillance to identify additional cases, searching both prospectively and retrospectively.
• If no evidence of ongoing transmission is discovered, then continue with routine infection control measures.
• If more than one case is found, environmental and epidemiologic investigations should be conducted to identify and eliminate the source of infection.
  • Collect environmental samples from potential sources, especially any implicated in the epidemiologic investigation. Use of settle plates is not effective due to the low concentration of Aspergillis spp. spores in the air. High-volume air samplers are recommended.
  • Aspergillus spp. obtained from patients and the environment should be sent for molecular subtyping to establish strain identity. (Draft note � the virology lab at DHMH performs species identification for A. fumigatus, A. flavus and A. niger. Strain subtyping involves use of restriction enzymes to create a DNA fingerprint and is not done at DHMH but may be done CDC.)
  • Inspect all elements of the environment designed to provide a protected environment for high-risk patients (e.g., effective HEPA filtration with sufficient number of air changes per hour, positive air pressure in patient rooms, airtight window seals).
  • Carefully inspect the air-handling system for malfunction and contamination.
  • Identify any recent or ongoing construction activities. Consider work done inside and also outside, adjacent to the hospital. Examine traffic patterns, movement of air, permeability of barriers etc. for possible sources of contamination to patient care areas.
  • If an environmental source of exposure is not identified, review existing infection-control measures, including engineering aspects, to identify potential areas that can be corrected or improved.
• Report an increase above your baseline rate or newly recognized ongoing transmission to your Local Health Department.

• Carter, C.D., Barr, B.A. (1997). Infection Control Issues in Construction and Renovation.Infection Control and Hospital Epidemiology, 18:587-596.
• Center for Disease Control and Prevention. Guidelines for Prevention of Nosocomial Pneumonia. Morbidity and Mortality Weekly Report 1997; 46 (No. RR-1).
• The Johns Hopkins Hospital. Infection Control Guidelines Related to Construction/Renovation. Interdisciplinary Clinical Practice Manual (IFC-005) 08-01-97.
• Last, J.M. (ed.). Public Health and Prevention Medicine (13^th ed.) New York: Appleton-Century-Crofts, 1992.
• Mandell, G.L., Bennett, J.E. and Dolin, R, Principles and Practice of Infectious Diseases, 4^th ed. New York: Churchill Livingston Inc., 1995.
• Wenzel, R.P. (ed.). Prevention and Control of Nosocomial Infections (3^rd ed.) Baltimore: Williams and Wilkins, 1997.

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