The CDC investigation of Legionnaires’ disease among patients at the VA Pittsburgh Healthcare System

CDC Congressional Testimony

Witness: Lauri Hicks, DO

Testimony – Testimony before the House Committee on Veterans’ Affairs Subcommittee on Oversight and Investigations United States House of Representatives

Good morning Mr. Chairman and other distinguished Members of the Committee. My name is Lauri Hicks, and I am a medical officer at the Centers for Disease Control and Prevention (CDC), within the Department of Health and Human Services. Thank you for the opportunity to speak to you today about CDC’s epidemic assistance investigation (Epi-Aid) into a Legionnaires’ disease outbreak at the Veterans Affairs (VA) Pittsburgh Healthcare System in Pittsburgh, Pennsylvania. I also want to extend my deepest sympathies to the patients and their families affected by this outbreak. Today, I will provide some background on Legionnaires’ disease and CDC’s role in these types of investigations. I will then provide specific details on CDC’s epidemic-assistance investigation (Epi-Aid) at the Pittsburgh VA Medical Center, a description of our findings, and our proposed recommendations.

Legionnaires’ disease

In 1976, CDC in cooperation with other Federal, State, and local authorities launched one of the largest joint disease investigations in history following an outbreak of severe pneumonia among the participants of the American Legion Convention in Philadelphia. This investigation led to the identification of the previously unrecognized bacterium, Legionella, and the establishment of Legionnaires’ disease (LD). Legionella is a type of bacteria found in fresh water. Outbreaks of legionellosis have occurred after persons have breathed mists that come from a manmade water source, such as building potable water systems (i.e., through exposure to faucets and showers), air conditioning cooling towers, whirlpool spas, or decorative fountains contaminated with Legionella bacteria. Most people who are exposed to Legionella do not get sick, but Legionella can cause a severe form of pneumonia, referred to as LD. The illness most often affects the elderly, those who smoke cigarettes or have chronic lung disease, and persons whose immune system are suppressed by diseases such as cancer, kidney failure requiring dialysis, or diabetes.

Legionella does not spread from person-to-person. LD can usually be successfully treated with antibiotics, but it does lead to death in 5-15 percent of cases. CDC estimates that between 8,000 and 18,000 people are hospitalized with LD in the United States each year.

Even though Legionella may be present in fresh water systems, finding it there does not necessarily mean it is the source of someone’s illness. There is not a clear relationship between the amount of Legionella in the water and risk for disease, and therefore there is no safe level of Legionella in a water system. When Legionella is identified in a water system, CDC recommends that measures be taken to remove the bacteria from the water, known as remediation. The most frequently used initial remediation measures include superheating or hyper-chlorinating the water system. These methods do not usually lead to permanent removal, so a long term plan for prevention of Legionella growth is almost always necessary.

The CDC role in epidemic assistance investigations (Epi-Aids)

CDC provides rapid assistance to States and Federal agencies, as well as international organizations and ministries of health, through formal requests for epidemic-assistance investigations (Epi-Aids). Since 1946, CDC has conducted more than 5,000 investigations. Epi-Aids always are performed collaboratively with the requesting partners and with the goal of controlling an epidemic and preventing future epidemics attributable to the same or related causes. The specific objectives of an investigation are to define the parameters of the epidemic (i.e., time of illness onset and conclusion of the epidemic, number of cases, and morbidity and mortality), to identify control or prevention measures, and possibly to identify new data relevant to the epidemiology of the health problem.

When CDC is invited to conduct an Epi-Aid, the general role of its investigators is to assist with: verifying the diagnosis and developing a list of hypotheses for the cause of the outbreak; establishing a case definition; collecting and analyzing data; categorizing cases as possible, probable, or confirmed on the basis of available data and knowledge; evaluating the hypotheses as to the outbreak’s cause based on the data collected; determining and implementing control measures; using surveillance to assess the control strategy; and writing and disseminating the final report. The report provides the requesting public health officials with an explanation of the extent of the outbreak and potential causes, which enables timely and effective public health action. The report identifies the risk factors that resulted in the epidemic, and it is disseminated to the health authorities and persons who requested assistance with the investigation.

CDC’s epidemic-assistance investigation (Epi-Aid) at the VA Pittsburgh Healthcare System

CDC works 24-7 to save lives and protect people from harm, and this investigation illustrates the power of public health in action both to identify serious health problems and to coordinate a targeted response that protects our nation and its citizens from infectious disease threats.

On October 5, 2012, the Pennsylvania Bureau of Laboratories contacted CDC Legionella laboratory to request subtyping of some Legionella isolates at the VA Pittsburgh Healthcare System (VAPHS). On October 12, 2012, CDC received two clinical isolates and one environmental isolate for sequence-based typing (SBT). On October 29, 2012, CDC reported preliminary results indicating a link between these two cases of LD with onsets of illness on August 25 and August 27, 2012 and an environmental Legionella isolate collected from the VAPHS University Drive Campus on October 3, 2012. CDC notified the Pennsylvania Department of Health (PA DOH), which notified the Allegheny County Health Department (ACHD) for further investigation. A conference call was held on November 5, 2012 with CDC, VAPHS and others and, upon learning of the results, the VAPHS Director promptly requested a visit from the CDC.

PA DOH requested an Epi-Aid on November 2, 2012. After discussion and with the agreement of VAPHS on November 6, 2012, CDC sent two Epidemic Intelligence Service (EIS) Officers and one microbiologist to Pittsburgh to join the ACHD and PA DOH EIS Officers and epidemiologists in the investigation. The field investigation began on November 7, 2012 and the last member of the field team left Pittsburgh on November 16, 2012. The objectives of this Epi-Aid were to: 1) Identify additional cases of LD among patients at VAPHS; 2) Complete an environmental assessment of LD risk and environmental sampling for Legionella at the hospital; and 3) Recommend interventions to prevent ongoing disease transmission.

For background purposes, I would like to provide a brief description of the VAPHS. The VAPHS serves the veteran population throughout the tri-state area of Pennsylvania, Ohio, and West Virginia, and has three campuses in Pittsburgh. The University Drive campus, “the hospital”, is a 150 bed acute-care hospital that opened in 1954 and provides inpatient and outpatient services. The H.J. Heinz campus houses primary care clinics, a long-term care facility, substance abuse program, and dental rehabilitation. The Highland Drive campus serves only administrative functions. Since 2007, electronic medical records have allowed computerized linkage of patient care information across all campuses.

In May 2004, VAPHS was approved for an almost $200 million major construction project and underwent extensive construction work on all campuses, beginning at the University Drive campus in January 2009.

VAPHS uses copper-silver ionization to control Legionella in its water distribution system. The process of copper-silver ionization releases positively-charged copper and silver ions into the water, which form electrostatic bonds with negatively charged bacteria cell walls. This bond is thought to disrupt bacterial cell walls and lead to cell death.


To identify additional cases, CDC queried two databases for LD cases occurring between January 1, 2011 and October 31, 2012. We searched the Pennsylvania National Electronic Disease Surveillance System (PA-NEDSS) for Legionnaires’ disease cases for which VAPHS was mentioned in the case entry. We also searched the VAPHS’s electronic medical records for positive laboratory results for Legionella-specific respiratory culture and Legionella urine antigen testing.

Using a medical chart abstraction form developed for this Epi-Aid, and with the help of the infection prevention team at the hospital, we classified cases into definitely healthcare-associated, probably healthcare-associated, and not healthcare-associated and collected epidemiologic, clinical, and exposure data on cases. A probable case had exposure to VAPHS, including but not limited to: overnight stay, outpatient visit, visitor, employee, and volunteer, during a portion of the 2-14 days prior to onset, and a clinical respiratory isolate was not available for molecular testing to confirm whether the clinical and environmental isolate were the same. We requested all available patient isolates for subtyping at CDC’s Legionella laboratory. VAPHS reported all new-onset cases directly to the Epi-Aid team following their departure from Pittsburgh.

We identified five definitely and 16 probably healthcare-associated cases of LD, for a total of 21 cases. All cases were patients who had been exposed to VAPHS before the CDC-recommended interventions were implemented. The median age of the 21 healthcare-associated case-patients was 64 years. All case-patients were male. All case-patients were Pennsylvania residents except for one from West Virginia. All cases were in patients at VAPHS; none were staff or visitors. Five case-patients or 24 percent died within 30 days of a positive diagnostic test for LD. All 21 cases had Legionella urinary antigen testing performed and nine of these also had Legionella-specific culture performed. In 13 cases, the exposure was only to the University Drive campus, in two cases only to the Heinz campus, and in six cases to both.

Environmental Assessment and Evaluation

The environmental investigation, which was conducted on the University Drive campus, began on November 7, 2012 with a visual inspection of the healthcare facility to determine possible sources of aerosolized water. This included patient care areas, waiting areas, decorative fountains, and cooling towers. We reviewed the potable water system, including visual inspection of the instantaneous hot water heaters and distribution system as well as three copper-silver ionization flow cells and controllers. Additionally, we reviewed blueprints and process flow diagrams of the potable water system with the facility manager.

We discussed the hospital’s layout, equipment, and maintenance practices with the hospital facilities and infection prevention staff. The staff provided verbal information and written records regarding construction work on campus and associated water outages; measured copper and silver levels, maintenance logs, and a consultative report; pH measurements; Legionella-specific culture results; date and site of emergency remediation measures; and their written protocol for Legionella risk-reduction.

Results of Environmental Sampling

For our environmental sampling for Legionella, CDC collected specimens in tandem with the hospital infection preventionists at their routine sampling locations. We also collected additional samples later that same day from patient care areas, central distribution points, and the decorative water fountain according to standard CDC sample collection protocol. We measured total chlorine, pH, and temperature and collected samples for copper and silver concentrations at representative locations throughout the potable water system.

Twenty-nine of 44 environmental samples collected by our field team in November showed growth of Legionella. Legionella grew from samples collected from various locations throughout the potable water system, including from all samples collected from sites immediately after the copper-silver systems, indicating widespread Legionella colonization throughout the hospital. Distal sites testing positive included patient care areas, the sink of the intensive care unit room of one probably healthcare-associated case, and a shower in a room used for liver transplant patients.

Clinical Legionella isolates from three cases were identical and matched environmental isolates collected from multiple locations in the hospital’s potable water system. This strain of Legionella was the outbreak strain. There were several other types of Legionella found in addition to the outbreak strain. Also, a sample from the sand filter of the decorative fountain at the entrance showed growth of the outbreak strain; therefore the fountain cannot be ruled out as a potential source of exposure for some cases.

Copper and silver levels were measured in 11 water samples in tandem with Legionella testing at routine sampling locations; seven samples were from distal sites, and four were collected from sites immediately before or after copper-silver flow cells. For copper, the mean concentration was 0.33 parts per million (ppm) at central sites, and 0.24 ppm at distal sites.

For silver, these mean concentrations were 0.04 and 0.02 ppm, respectively. Seven of 11 samples were within the manufacturer’s recommended range for Legionella control for both copper and silver. However, all 11 samples showed growth of Legionella, and nine were positive for the outbreak strain. Our environmental assessment and evaluation identified the following factors and policies that contributed to the outbreak:

  • There was persistence of a highly pathogenic strain of Legionella in the potable water system despite copper-silver ionization and intermittent superheating during the past two years. At the time of our investigation, the copper and silver levels in the water were appropriate for controlling Legionella according to the manufacturer’s recommendations and the hospital’s protocol. However, these same samples still tested positive for Legionella, indicating that the copper-silver ionization system was not controlling Legionella growth. The diversity of species, serogroups, and serotypes among Legionella isolates makes resistance to copper-silver ionization an unlikely explanation for amplification within the system, and points to an environment adequate for Legionella growth, indicating a systemic problem that was not being controlled by the copper-silver ionization system at the time of sample collection. The hospital collected small volumes (100 ml) of water for routine culture-based monitoring of the potable water system for Legionella. Compared to the 1 L volumes recommended by CDC, this smaller volume likely resulted in decreased sensitivity to detect widespread colonization of the potable water system.
  • The hospital relied upon an action threshold (30 percent of distal sites positive) to prompt remediation. Cases occurred when sampling indicated that less than 30 percent of sites were colonized. A recent review determined that the 30 percent threshold provides both low specificity (74 percent) and sensitivity (59 percent) for legionellosis risk assessment. CDC’s records on known outbreaks from 2011 revealed two outbreaks where Legionnaires’ disease cases occurred after exposure to building water systems with Legionella positivity at less than 30 percent of distal sites.
  • The hospital has been undergoing extensive construction. The timing of construction work at the hospital coincides with the outbreak. Construction likely introduced organic matter to the potable water system, increasing consumption of chlorine in the municipal water supply leading to amplification of Legionella. Residual chlorine in the water system, although at adequate levels in the incoming municipal water supply, was at an insufficient concentration for microbicidal activity at all distal sites measured within the hospital.

In addition, the following epidemiologic and surveillance factors were found to contribute to the outbreak:

  • The hospital did not recognize healthcare-associated cases of LD for an extended period of time. A low index of suspicion that lab-confirmed cases were healthcare-acquired can be partially attributed to a perception of Legionella control in the hospital water systems.
  • The cases reported to county and state public health offices were not recognized to be healthcare-associated and part of an outbreak. This may be due to a high baseline prevalence of Legionnaires’ disease in Pittsburgh.

CDC’s Findings and Recommendations

CDC findings and recommended interventions to prevent ongoing transmission of LD at the VAPHS have been detailed in a report provided to the VAPHS and the PA DOH.

The CDC investigation revealed a large number of healthcare-associated LD cases during 2011-2012 and widespread colonization of Legionella in the hospital’s potable water system. These cases occurred in the setting of a comprehensive Legionella risk-reduction program consistent with national Veterans Affairs and county health department guidelines. This program included disease surveillance, environmental testing, and a long-term disinfection system for control of Legionella in the potable water.

CDC made some initial recommendations to stop disease transmission, which included:

  • Minimize patient exposure to potable water sources. There are several ways to do this, including restricting patient showering, restricting drinking from potable water sources, installing point-of-use filters for faucets and showerheads, and turning off all decorative water features and whirlpool spas until remediation strategies have been shown to be effective.
  • Implement short-term systematic potable water system remediation as referenced in American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. ASHRAE Guideline 12-2000: Minimizing the risk of legionellosis associated with building water systems, 2000:
    • Hyperchlorination to greater than or equal to 2 ppm at all distal sites and flushing at all points of use , and/or
    • Superheating and flushing of the potable water system to 160-170 degrees.

CDC also recommended enhanced testing and surveillance for LD to identify any new cases.

Additionally, CDC made recommendations for long-term Legionella control measures, including:

  • The long-term disinfection system for prevention of Legionella growth in the hospital’s potable water system should be reevaluated in consultation with experts.
  • The facility should strive for eradication of Legionella from the potable water system, as there is no known safe level of Legionella.
  • The hospital should continue testing for Legionella every two weeks for three months, and then every month for three months to ensure remediation has been effective. If any Legionella is detected during this time frame, remediation throughout the facility will need to be adjusted and the testing cycle must start over.
  • LD surveillance should be conducted at the hospital according to CDC recommendations, with a strict case definition and action upon identifying one definite or two possible healthcare-associated cases.
  • Close communication among hospital staff and between the hospital and public health would improve surveillance.
  • The Legionella control protocols of the hospital, the Veterans Health Administration, and the Allegheny County Health Department should be carefully reevaluated to include changes in surveillance methodology, including action thresholds and sampling methods.
  • The hospital should modify their Legionella sample collection procedures. Both swabs and 1L water bottles should be collected at various sampling sites, with samples processed as soon after collection as possible and results communicated to infection preventionists, building facilities manager, hospital administrators, and CDC. Chlorine, pH, and maximum temperature should be measured at the water heaters and at least a couple of distal sites.
  • A standard operating procedure for appropriate maintenance, including regular cleaning, of decorative fountains should be drafted and followed. Facility managers should consult with the manufacturer of the decorative fountain to determine an acceptable biocide for Legionella control.


The VAPHS has rapidly implemented CDC’s recommendations and has taken several steps to protect patient safety. The hospital shut down their potable water system on November 15, 2012 to initiate remediation. Meanwhile, a combination of bottled water and point-of-use filters were used for patient care needs. Superheating and hyperchlorination were performed, followed by installation of a chlorine drip to maintain the chlorine level at approximately 1-2 ppm throughout the system. Repeat sampling two weeks later showed that remediation was successful, and water usage restrictions were lifted on November 30, and the VAPHS declared the water system clear of Legionella. To date, no further LD cases have been detected. I would be happy to answer any questions the Committee may have.

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