Q&A: CDC town hall addresses preventing Legionella contamination
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November 1, 2017
Editor’s note: On June 2, CMS issued a new memo to surveyors on the importance of reducing cases of Legionella infections. Not long after, the CDC issued a Vital Signs report underlining the bacterium’s risk to patients. First discovered in the 1970s, the Legionella bacterium can cause a type of pneumonia called legionnaires’ disease (LD), which kills about one-quarter of the people who contract it. The bacterium thrives in warm water and is spread through breathing aerosolized water droplets. It’s especially dangerous for patients who are older than 50, who smoke, or who have chronic lung or immunosuppression conditions.
The following is an edited Q&A from the CDC Vital Signs Town Hall, “Health Care-Associated Legionnaires’ Disease: Protect Patients With Prevention and Early Recognition.” Speakers included Elizabeth Soda, MD, CDC epidemic intelligence service officer, Jeff Duchin, MD, health officer of public health at Seattle & King County, John Letson, MBA, vice president of plant operations at Memorial Sloan Kettering (MSK) Cancer Center, Laura Cooley, MD, MPHTM, CDC medical epidemiologist, and Jasen Kunz, MPH, REHS, CDC environmental health officer. Two new studies have found that, while patient-centered medical homes (PCMH) help improve patient outcomes, it’s difficult to quantify their impact on overall healthcare spending.
Q: What are the current CDC recommendations on when to have a Legionella investigation in a healthcare setting?
Soda: There might be a gray area around this, but the CDC currently recommends an investigation in two scenarios.
First, we recommend an investigation for any one definite healthcare-associated case. We define a definite case as a patient who’s had continuous exposure to a hospital or long-term care facility for the entire 10 days preceding onset. Because really that patient only had exposure to a water system within that healthcare facility. So it’s probable that the healthcare water system was the source of this case of exposure. Thus the investigation is warranted.
Second, we recommend an investigation if two or more cases are possibly linked to a facility within 12 months of each other. A possible case is any patient who’s had exposure to a healthcare facility for a portion of the 10 days preceding such an onset. Two cases of possibly associated cases from the same facility raise concerns of that source for on-going transmission to others.
Q: Can you elaborate on the possible confusion over Legionella guidelines?
Duchin: The 2003 guidelines for environmental infection control in healthcare facilities and the IMPACT guidelines for preventing healthcare-associated pneumonia (HAP) have criteria for facilities to initiate an environmental investigation after Legionella cases are confirmed or suspected.
These 2003 guidelines basically use a criterion to determine whether or not a healthcare facility has a severely immunocompromised patient (such as solid organ transplant patient) for establishing whether or not an environmental investigation is indicated after one confirmed case. The old guidelines, 2003 guidelines, state that if your facility doesn’t have severely immunocompromised patients, it’s perfectly acceptable to [wait and] observe and see if a second case occurs before initiating an environmental investigation.
However, current guidelines such as the CDC Legionella toolkit really don’t use that criteria of severely immunocompromised patients any longer. [Instead,] they refer to healthcare facilities having any patients at increased risk of LD. That’s pretty much anyone you find in a hospital because it includes chronic pulmonary disease, cardiac disease, smoking, and various forms of immunocompromise (not just the severely compromised patients who are called out in the 2003 guidelines).
So the basic change is that after one confirmed case, the current criteria suggests that environmental investigation is appropriate. The old guideline says after one confirmed case, whether you do an environmental investigation depends upon if you have a severely immunocompromised patient in your facility.
Cooley: Basically, the way we approached it here [at CDC] on the Legionella team is that I think that [our] IMPACT guide came out in 2003. The population is aging, more and more people are immunocompromised, there are newer immune-suppressing medications available for a wide variety of diseases. So we altered our interpretation to include all at-risk populations and, as Dr. Duchin said, that’s all of the people in the hospital. But definitely more than just the most severely immunocompromised patients would be at risk for LD.
Q: In absence of a patient case, does CDC have any recommendations on when to treat the water based on colony-forming units (CFU.) In other words, how many CFUs do you need before treating the water?
Cooley: We get that question all the time, and I think it’s really case-by-case specific. It seems like what you’re asking about is more the prevention side rather than the outbreak response side.
We generally don’t look at any threshold as a safe level. I think instead of saying zero tolerance [for Legionella], we’d say, “We don’t know of any safe levels of Legionella.” It’s not that we think hospitals aren’t going to find Legionella while doing routine managing [of] their water; they will. But we’re talking about outside of a disease case, and that’s the importance of the water management program.
If they find Legionella, no matter what level the Legionella is, there should be something that’s triggered in its water management program to investigate why that happened, looking at the parameters, disinfectant levels, temperature, and if there’s been any stagnant water upstream. Really revisiting what’s been going on in the water system and making corrections and then following this over time.
There’s a lot of significance to [looking for] more than just a strict level of Legionella, but [looking instead] to trends over time. But even if it’s at low levels, if there’s one area that’s consistently positive during routine testing, then that’s a problem. And so it would be important at that time for the water management team to investigate the water management program and the water system.