Task Force/Recommendations For Acute Care

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Task Force Overview

In preparing recommendations, the Texas Legionnaires' Disease Task Force carefully considered the work of the Maryland Scientific Working Group, the published guidelines of the CDC, and the opinions of other prominent researchers in the field. The recommendations presented below reflect the expert opinion of the Texas Legionnaires' Disease Task Force, drawing on available published data and the expertise and experience of Task Force members.

Many of the recommendations are intended for physicians and hospitals, because the people at greatest risk of acquiring legionellosis are immunocompromised and/or chronically and seriously ill patients who are hospitalized or are outpatients under the care of a physician. The Task Force also made recommendations for nursing homes and other LTCFs that serve as permanent residences for medically fragile individuals. Finally, the Legionnaires' Disease Task Force developed some guidelines to assist health departments and physicians address sporadic, community-acquired cases.

The Legionnaires' Disease Task Force recognizes that no single template can serve the needs of all types of facilities, and strongly supports an approach that allows institutions to individualize their legionellosis control plans based on the history of their institution; the matrix of environmental factors, engineering issues, and patient populations served by the institution; and the resources the institution has available to address these concerns.

The Task Force does intend for each institution to consider the factors that may contribute to legionellosis transmission and diagnosis in their context and to develop a control plan or plan of action that increases physician awareness of the disease, increases the diagnostic capability of that institution, and enhances the institution's ability to prevent disease.

Each hospital should form a team of representatives from various departments such as infection control, engineering and maintenance, risk management, employee health, administration, and housekeeping to prevent and control legionellosis.

The team should develop and write a legionellosis control plan. The team shall be led by a hospital epidemiologist or an infection control professional. This operational plan should encompass several components including:

  1. Surveillance strategies
  2. Whether environmental culturing is recommended
  3. Remediation strategies (if and when necessary)
  4. Reporting procedures

Diagnostic Capacity

I. Differential: Clinicians should consider Legionella species in their differential diagnosis for both nosocomial and community-acquired pneumonia. Appropriate diagnostic specimens should be obtained before initiating treatment.

II. Urine Antigen: All acute-care hospitals should either provide Legionella urinary antigen testing in-house, or contract with another laboratory that can report test results within 48 hours.

III. Cultures: All hospitals that routinely perform and care for patients with solid organ and/or bone marrow transplants should have the ability to perform Legionella culture on site. All others should have a mechanism in place that allows them to submit primary specimens for Legionella cultures to a microbiology laboratory within 24 hours of specimen collection.

IV. DSHS as Reference: The DSHS laboratory serves as a secondary reference laboratory for Legionella, with the capability to serotype, speciate, and characterize isolates on a molecular basis. Specimens from possible and definite nosocomial cases should be forwarded to the DSHS.


I. Passive Case Detection

A. A hospital laboratory should notify the infection control practitioner at the hospital within one day of positive results from a Legionella culture, urine antigen test, direct fluorescent antibody test, or a paired serum antibody test (see case definition for legionellosis).

B. If a patient with laboratory evidence of legionellosis has an illness clinically compatible with legionellosis (Legionnaires' disease or Pontiac fever), then the patient has confirmed Legionnaires' disease or Pontiac fever.

C. Confirmed Legionnaires' disease or Pontiac fever cases should be further investigated to determine whether they meet the case definition for nosocomial illness (see case definition for nosocomial legionellosis). A thorough epidemiologic and environmental investigation should be conducted to determine the likely environmental sources. Hospitals that need assistance with an investigation should call their local health department.

D. Confirmed cases of Legionnaires' disease or Pontiac fever should be reported to the local health department (800-705-8868) as "definitely nosocomial," "possibly nosocomial," or "not nosocomial" cases within one week of confirmed diagnosis. The report should be submitted on DSHS IDCU Form 5, 02/02; [Form] to the local health department. The local health department should also report to DSHS within one week of confirmed diagnosis.

E. Outbreaks (defined as two or more institutionally linked cases within the same 6-month period) must be reported immediately to the local health department at 1-800-705-8868.

II. Active Case Detection
When a hospital has a possible or definite nosocomial case, active surveillance must be implemented.

A. Test specimens from patients with pneumonia: Institutions should develop "in-house" legionellosis case-finding strategies. This may include algorithms recommending that the following tests be performed on specimens from high risk patients with pneumonia:

1) Culturing of sputa.
2) Antigen testing of urine.
3) Culturing and/or direct fluorescent antibody testing of bronchoscopy specimens.

B. Evaluate sputa and x-rays: At a minimum, active surveillance should include daily review of all sputum cultures and chest x-rays. It should include daily review of newly diagnosed pneumonia cases. Once implemented in response to a possible or definite case, active surveillance should continue for at least six months.

Environmental Testing

Environmental testing, in the context of legionellosis, is the sampling of water and plumbing structures of a facility's water distribution system. The Texas Legionnaires' Disease Task Force discussed the role of environmental testing as a surveillance measure and investigational tool at great length.

There are currently two different views in the United States on the role of environmental testing. One group holds that environmental testing should only proceed once an outbreak or definite transmission has been identified. Another group proposes that all hospitals routinely culture for environmental Legionella.

Adoption of the first position, as done by the CDC, could place certain patient populations at increased risk for acquiring Legionnaires' disease; the potential risk to such patients can only be ascertained by environmental testing. Recent research in Texas has shown that there are wide disparities between facilities' water systems in Legionella colonization [1].

Adoption of the second position, as done by the Allegheny County Health Department and the State of Maryland, commits large numbers of facilities to regular investments of resources that may be disproportionate to the risk involved and in fact may damage the infection control capacity of a given facility by diverting staff time and resources away from other, potentially more pressing, infection control concerns.

Drawing on elements from both the CDC position and the position outlined in the report produced by the Scientific Working Group in the State of Maryland, the Texas Legionnaires' Disease Task Force developed the following recommendations for healthcare facilities:

I. Assessment of Legionellosis Risk and Criteria for Environmental (Water Distribution System) Testing

All healthcare facilities should, in implementing their legionellosis control plan, assess their risk of legionellosis transmission. Each facility should evaluate environmental, engineering, and patient population factors to determine whether there is a reasonable potential for nosocomial transmission. Baseline water distribution system cultures should be performed if the results of the assessment indicate the facility has a significant risk of legionellosis transmission.

Factors that affect the risk of nosocomial transmission in a given facility are as follows:

A. Environmental factors

1. Water chlorination. Recent research [1,57,58] suggests that how the water is treated in a given community can influence Legionella colonization of hospital water systems. Water sources that provide low levels of free chlorine as a residual disinfectant may be at increased risk when compared with water sources that use monochloramine as the chemical residual disinfectant. While this issue needs further study, hospital staff should work with their water supply agency to determine how the water from the municipal supply is treated.

 2. Temperature. Legionella bacteria are thermophilic and grow best between 25-42oC (77-108oF). If water is stored in tanks in this temperature range or delivered to patient care areas at a temperature within this range, there is a reasonable risk that Legionella species will be living in the distribution system.

B. Engineering factors
The following water system characteristics have been associated with the growth of Legionella:

1. Vertical configuration (e.g., multistory building) [64]
2. Dead legs [21,64]
3. Water heaters arranged in parallel [64]
4. Dead space at the bottom of the heaters [64]
5. Silicone-based rubber plumbing products [64]
6. Water softeners [21] 7. Aerators or shower heads in high risk patient areas that aren't cleaned or replaced regularly (association is suspect but plausible)[61]

C. Patient mix
The following patient populations are all at increased risk for legionellosis, and any facility that treats these patients is at increased risk for disease to occur. Immunocompromised employees may also be at increased risk.

1. Solid organ transplant patients.
2. Bone marrow transplant patients.
3. Patients with cancer undergoing chemotherapy.
4. Patients diagnosed with chronic obstructive pulmonary disease.

D. Prior history
A prior history of either of the following may increase the risk of transmission:

1. History of nosocomial legionellosis identified among patients.
2. History of positive water cultures from the potable water system and outlets or cooling towers.

The Task Force recommends that each facility consider these factors in determining whether there is an increased risk of nosocomial transmission. An example of how such a determination may be made is as follows: any facility located in a community where free chlorine is used as a residual disinfectant, that is a multistory facility with multiple water distribution systems, where hot water is stored at 51oC (124oF) and delivered to patient care areas at no greater than 43oC (110oF), with patients receiving bone marrow or solid organ transplants or cancer patients undergoing chemotherapy present, would be considered a facility that is at increased risk for nosocomial transmission. Such a facility should conduct a baseline environmental assessment, including Legionella tests of water samples from water distribution endpoints, and maintain these data on file in the infection control program office and the facility engineer's office. If, however, the facility is a one story rehabilitation hospital with a limited number of beds and a simple plumbing design, with no dead legs in the system, in a community where monochloramine is used as a residual chemical disinfectant, and no immunosuppressed patients are present, the factors increasing the facility's risk for transmission would not be present and there would be no recommendation for an environmental assessment at this time.

II. Procedures for Environmental (Water Distribution System) Testing

A. Water distribution system culturing should only be done after one of the following criteria are met:

1. Baseline assessment of risk indicates that there is a significant risk of nosocomial transmission.
2. There are one or more definite nosocomial cases or two or more possible nosocomial cases.
3. Remediation has been completed.

B. Water distribution system testing should be conducted according to a standard protocol:

1. Refer to Appendix C for specific procedures to use when conducting baseline water distribution system testing and any follow-up testing required by the infection control committee.
2. The Legionella control team should be involved in designing the testing protocol for the facility.
3. The Legionella control team should contract with firms experienced in obtaining specimens for water distribution system culturing of Legionella.

C. Legionella cultures should be qualitative and not quantitative.

D. Serotyping and species identification should be included in the results; hospitals unable to speciate or serotype should send samples to a reference laboratory.

E. When cultures of the water distribution system yield Legionella, the hospital's physicians should be informed to heighten awareness of Legionella as a potential cause of nosocomial pneumonia.

In keeping with the spirit of the State of Maryland Report of the Scientific Working Group and the Allegheny County, PA, recommendations, the intent of the Texas Task Force is not to insist that hospitals must have culture-negative water systems; it is recognized that persistence of Legionella in many instances will be inevitable, and may be of minimal significance from a public health standpoint.

All hospitals are expected to maintain good surveillance for nosocomial Legionella cases; identification of a nosocomial case should be a clear indication that further efforts must be made to reduce Legionella colonization of the water supply. Hospitals that do not have the infection control expertise to interpret data should work with the local health department, and may need to retain the services of an expert in this field. However, except in special circumstances (such as an outbreak), water distribution system culture results should not be routinely reported to the health department.


Prevention strategies for Legionella pneumonia should be developed and implemented by all acute-care hospitals in Texas as part of each facility's legionellosis control plan.

I. Primary Prevention

A. Prevention of Legionellosis in Hospitals with No Identified Cases and in Those with No Testing or Negative Baseline Water Distribution System Testing

1. Education:
Educate (a) physicians to heighten their suspicion for cases of nosocomial Legionnaires' disease and to use appropriate methods for its diagnosis, and (b) patient-care, infection-control, and engineering personnel about measures to control nosocomial legionellosis.
2. Equipment cleanliness:

a. Nebulizers and other semicritical respiratory care equipment should be cleaned with sterile water.
b. Enteral tubes should be flushed with sterile water and enteral feedings should be diluted with sterile water [26,27].

3. Facility and physical plant control measures:

a. Cooling towers should be designed and constructed so that tower drift is directed away from the hospital's air intake system and the volume or aerosol drift is minimized.
For all operational cooling towers, hospitals should:

1) Install drift eliminators.
2) Use a biocide regularly.
3) Maintain towers according to manufacturers’ recommendations.
4) Keep adequate maintenance records.

b. Units with high-risk patients should not use large volume humidifiers that create aerosols unless they are treated with a high level disinfectant daily.

B. Prevention of Legionellosis in Hospitals with No Identified Cases but with Positive Baseline Water Distribution System Testing (>30% Distal Sites Culture-Positive for Legionella)

1. One long-term study has documented the occurrence of Legionnaires' disease cases in a facility when >30% of distal sites test positive for Legionella, and no cases of the disease when fewer sites test positive [60].
2. Enhanced surveillance:

a. Legionella testing should be conducted for 60 days for all nosocomial pneumonia cases that occur two or more days after hospitalization.
b. The availability of laboratory tests for Legionella should be assessed; in the presence of one definite case, new suspect cases should have cultures performed in addition to any rapid tests.
c. Recent pneumonia cases should be reviewed for possible diagnosis as legionellosis. Collect urine specimens on nosocomial pneumonia cases that occurred within the last 60 days and test them with a Legionella urine antigen test, when appropriate.
d. The possibility of hospital-acquired cases among employees should be considered.
e. Cultures of water systems and other potential sources (of Legionella) should be conducted.
f. Case-control studies should be initiated, if appropriate.

3. Remediation:
Remediation efforts should be initiated immediately to reduce levels of Legionella colonization in the hospital water system. Approaches to remediation may differ from institution to institution, and should be developed in consultation with engineers or public health officials familiar with Legionella control programs. The ASHRAE guidelines [59] are a reference source for approaches to Legionella control within water systems.

a. Potential remediation efforts include:

i. Superheating of water.
ii. Hyperchlorination.
iii. Copper-Silver ionization.
iv. Monochloramine treatment.
v. Ultraviolet treatment.

b. Where practicable, the following engineering measures should be incorporated into the design and operation of the water system:

i. Instantaneous or semiinstantaneous water heaters should be used instead of tanks. If tanks are used, horizontal tanks are preferred over vertical tanks, and steps should be taken to maintain adequate circulation to minimize cool spots within tanks. Hot water system recirculation pumps should run continuously.
ii. For optimal control of Legionella bacteria, hot water should be generated or stored at or above 60oC (140oF) and reduced to 50oC (122oF) for distribution.
iii. Installation of fail-safe thermostatic mixing valves and pressure independent mixing valves will permit maintaining a higher temperature in the water distribution system while minimizing the risk of scalding.
iv. The design should eliminate "dead legs" and other areas of stagnant water. Standby pumps and piping connections should be cycled regularly. The hot water recirculating system should be installed to serve the fixture farthest from supply.
v. Studies indicate that copper is the most resistant of piping materials for Legionella colonization. Natural rubber gaskets should be avoided.
vi. Careful attention must be paid to the materials and workmanship of pipe insulation. This will help keep hot water pipes hot, and cold water pipes cold.
vii. The water storage and distribution systems should be cleaned and descaled where appropriate.

(Notes: Recommendations for immediate remediation have been previously published by the CDC in the Guidelines for Prevention of Nosocomial Pneumonia [14]; and are covered in the ASHRAE [59] and Allegheny County guidelines [61]. Development of long-term remediation plans will require consultation with experts in this field. The CDC position that remediation efforts should be continued until all environmental cultures are negative may be unrealistic. Depending on the risk profile of the facility, a significant reduction in the number of colonized distal sites may be an acceptable endpoint.)

4. Protection of high risk patients:
Consideration of other methods to limit exposure of high risk patients to potentially contaminated water sources, pending successful reduction in levels of Legionella colonization within the hospital water system include:

a. Possible restrictions on showering.
b. Consider restrictions on use of potable hot water: shift to using sterile water for bathing, drinking, oral hygiene, wound care, and dilution of drinks and G-tube feedings.

II. Secondary Prevention: Prevention of Legionellosis in Hospitals with Identified Cases Identification of one definite or two possible nosocomial Legionella cases within a 6 month period should initiate the preventive measures described in IB above (Prevention of legionellosis in hospitals with no identified cases but with positive baseline water distribution system testing [>30% distal sites culture positive for Legionella]).