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Q&A: CDC town hall addresses preventing Legionella contamination


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. 

Q: To Dr. Duchin, you mentioned the restriction of showers and the use of bottled water for drinking at your facility during your environmental investigation. I was wondering if you’d recommend this kind of restriction before you had recent environmental results. Also, if your water restrictions are being instituted, what would be the strategy to then remove a facility from water restrictions and back to using showers and drinking water?

Duchin: What happened here locally was that the restrictions that were put in place by this healthcare facility included restricted showers, using bottled water, and stopping the use of the ice machines until inline filters could be put in place, and putting point-of-use filters at all patient use areas. Those restrictions stayed in place until an assessment was done, water management remediation steps were taken, and the first set of negative cultures were available two weeks after the initial remediation. I still believe the facility is using the point-of-use filters.

As for when’s the right time to implement, our guidance was to minimize exposure to potable water immediately, including the use of showers. The use of bottled water and filters was more challenging to recommend until you have some idea what the environmental source is, whether it’s cooling tower vs. potable water in the facility. So to some degree you have to depend on what you think the source is and then discover the risk overhead equation—how much risk they’re willing to take and how much cost they can assume in making a response before they actually pin down a problem.

 And that’s a few of the things that our hospital was thinking about: How much is it going to cost? How long can we do it? What’s the best timing?

I’d be very interested to hear what our CDC colleagues recommend in this context as well.

Cooley: That was an excellent answer, and I don’t think there’s a lot to add to that. I do want to say that water restrictions have to be tailored to the circumstances of the outbreak and the structure of the facility because there are going to be so many different variables.

I think that the key, overriding principle here is, if there’s a possible source of Legionella transmission that hasn’t been identified yet or there hasn’t been any kind of remediation effort, there’s still an ongoing risk. The key is to protect vulnerable patients there from further cases of LD. That’s why water restrictions and other options, like point-of-use filters on showers and faucets, are intended to protect vulnerable patients to exposure from any ongoing risk.

No matter what options you choose, how long do they last? And there’s no hard-and-fast rule for that, but I think that’s when the team investigating feels like they’ve identified and controlled the source and adequate remediation has been performed.

It basically comes down to what does the investigative team assess as the risk and how long is that risk still credible. And as long as they think there’s a risk to others, those restrictions should stay in place.

Q: What do you see as the biggest challenge to fighting Legionella in the future?

Letson: The greatest challenge (and it’s of biblical proportions) is an attempt to control the community-acquired Legionella (CAL). I think this becomes important as more and more cancer treatment is turning to outpatient care, facilities closer to patients’ homes. As a result, I think that when these patients who are immunocompromised go back home, [they] might be exposed to Legionella in whatever water systems are outside the healthcare environment: in their homes, in hotels, wherever they might be staying or going while they’re undergoing treatment.

This becomes particularly important for us too because MSK is looking for a lot of the treatment for bone marrow transplant to move into the outpatient arena. Going forward, as we discharge patients and try to get them home sooner, [we are trying] to improve their quality of life and get them back on the road to normalcy. I think that CAL, getting that under control, is going to be the greatest challenge.

Q: One of the biggest challenges for public health officials is knowing when to notify the public that a Legionella investigation is happening. You talk about initially notifying the patients and then the public. How did you come up with that, and what criteria did you use for the problem of notification?

Duchin: We used the traditional criteria that many hospitals across the country use, which includes:

  • Is there an ongoing risk to people in the general public?
  • Can people take action to protect themselves?
  • Is something happening that is very unique, unusual, or newsworthy?

We’re also a bit more proactive in that outbreaks that can occur in smaller groups can also become public. It’s [in] the best interest of both healthcare facilities and the communities involved to be very transparent about these situations.

For example, in an outbreak of Legionella where we are notified by a large number of healthcare providers and a large number of patients, it makes sense to also do a public notification. Because we believe that information to be very likely to become public, it’s better to get accurate, timely information out to the public proactively, rather than [have] a patient or a provider raise that issue with a media outlet and give the impression that the healthcare facility or agency was intentionally not informing the public about a problem.

We became very sensitized to this a couple of years ago when we had a large outbreak at a local hospital. The outbreak was well controlled and all the patients were promptly notified. However, a public announcement was not made even though the information was presented at public meetings; there were no general public announcements. And there was a series of scathing media reports about what was interpreted as a cover-up by that facility, which, in fact, had done everything right. They recognized the problem, reported it promptly, notified the patients, put infection control measures in place—everything except the public notification, and they really took a beating for it.

We [at Seattle & King County] got together with our healthcare communities at that time and decided collectively it’s better to be transparent about these events as promptly as possible whenever we can.

Q: Can you talk about Legionella contamination in ice machines?

 Kunz: Ice machines obviously can present a risk of colonization due to their design. For ice to become cold, they have to remove heat from it. So there’s heat being dispersed, and lines within ice machines might become warm and bio-film might grow. And if there’s Legionella coming in sporadically through your distribution system, it could colonize that ice machine.

Ice machines in healthcare institutions [should] certainly be part of the water management plan. They would have periodic cleaning and other operation and maintenance deemed appropriate by the manufacturer and the water management team. And it’s up to the facility to determine if periodic testing for Legionella is warranted within those ice machines.

Q: We normally have testing done on our hot water, but now we have an issue with ice and Legionella. Do we need to look into testing both cold and hot water throughout the building? And the municipal water we have coming in doesn’t even test for Legionella, so we have no idea what the levels are for that.

Kunz: One of the things important to note in a building water system is that conditions within the building itself can degrade the quality of the potable water of the municipal water utility. Theoretically, you could have properly finished water coming into the facility and something could go on in that facility that creates stagnation and warms the water. In this particular case, it’s the ice machine where bio-film could build up, which could become a potential reservoir where Legionella could grow.

Sometimes even the filters themselves inside these ice machines can be reservoirs for Legionella depending on what the composition of that filter material is. Specifically, if there’s maybe carbon filters in place on these machines that are designed to be removed, some of the taste and odor can actually have Legionella growing in there.

Those are the various aspects of the operation and maintenance of the ice machines in there. Those are operation and maintenance of the ice machines that you should consider.

In terms of looking at the actual cold water coming in, we recommend you establish a control point at that water distribution where it enters the building, [including] any main you have coming into the healthcare facility. And within that control point, we’d recommend monitoring for chlorine and disinfectant levels coming in from your facility. You want to look at total chlorine as an estimate for monochlorine. Put that into your regular rotation in terms of control points. We’d also advise you to create a dialogue with the water treatment plans. I think there’s synergy between the two in terms of effective water management.

One of the things you should be looking for in the healthcare institution is if there’s any water main breaks or pressure disruptions or changes in the types of water quality coming in. [For example,] whether you’re seeing no chlorine levels or dirtier groundwater.

Then if you see a disruption or disturbance in the water, you have a predetermined plan to react to that within the hospital to bring that water back to normal. Also, trying to communicate with water utility if you start to see changes in the water. It would also [be] great to get a heads-up from the water utility if possible if planning to do any type of maintenance or things that could disturb the water flowing into the facility.

It’s going to be up to hospitals ultimately to determine if they want to do any testing for Legionella on that cold water, recognizing that it can often be more difficult to [take] a culture for Legionella on cold water—also recognizing in the summertime, our cold water temperatures rise depending on what part of the country you’re in.


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