The CDC released a Morbidity and Mortality Weekly Report (MMWR)(www.cdc.gov) and an accompanying Vital Signs report on June 6 that analyzed the prevalence of Legionnaires' disease in the U.S. health care system and found that 76 percent of facilities studied reported health care-associated cases of the disease.

Seventy-two health care facilities in 16 of the 21 U.S. jurisdictions the CDC studied reported definite health care-related cases of Legionnaires' disease, which is known to kill one-quarter of patients who are infected.

Legionnaires' disease is a severe pneumonia typically acquired through inhalation of aerosolized water containing Legionella bacteria. Legionella can grow in the complex water systems that supply many buildings, including health care facilities, when those systems are not well managed. Thus, effective water management programs could prevent the growth of Legionella in these building water systems.

Most healthy patients who are exposed to Legionella don't develop Legionnaires' disease. Some patients, however, are at increased risk for the disease, including those 50 or older and those who have certain risk factors, such as being a current or former smoker or having a chronic disease or weakened immune system.

Legionnaires' disease in hospitals is widespread, deadly and preventable," said CDC Acting Director Anne Schuchat, M.D., in a June 6 news release.(www.cdc.gov) "These data are especially important for health care facility leaders, doctors and facility managers because it reminds them to think about the risks of Legionella in their facility and to take action.

"Controlling these bacteria in water systems can be challenging, but it is essential to protect patients."

All 50 states, two large U.S. metropolitan areas and five territories report basic demographic information to the CDC's National Notifiable Diseases Surveillance System (NNDSS) for all cases of legionellosis, which manifests as one of two distinct clinical presentations: Pontiac fever (a mild influenza-like illness) and Legionnaires' disease. NNDSS makes no distinction between the two presentations.

In 2015, a total of 6,079 cases of legionellosis were reported to NNDSS, although the CDC noted that this estimate may be low due to underdiagnosis. The Supplemental Legionnaires' Disease Surveillance System (SLDSS) receives additional epidemiologic information, including whether patients were exposed to health care facilities, and distinguishes Legionnaires' disease from Pontiac fever, but reporting to SLDSS is less widespread.

The MMWR analysis aimed to define which Legionnaires' cases were associated specifically with health care facilities using data from the 21 U.S. jurisdictions. Definite health care-associated disease was defined as including hospitalization or long-term care facility residence for 10 days preceding symptom onset; possible health care-associated disease was defined as including any exposure to a health care facility for a portion of the 10 days preceding symptom onset. All other cases were considered unrelated to health care.

The MMWR analysis aimed to define which Legionnaires' cases were associated specifically with health care facilities using data from the 21 U.S. jurisdictions. Definite health care-associated disease was defined as including hospitalization or long-term care facility residence for 10 days preceding symptom onset; possible health care-associated disease was defined as including any exposure to a health care facility for a portion of the 10 days preceding symptom onset. All other cases were considered unrelated to health care.

Of the more than 6,000 confirmed legionellosis cases reported to NNDSS in 2015, 3,516 (58 percent) were also reported to SLDSS, including 3,459 Legionnaires' disease cases. Of those Legionnaires' disease cases, 2,809 (81 percent) were reported by the 21 jurisdictions included in the MMWR analysis, including 553 (20 percent) that were health care-associated (either definite or possible).

Of the 85 Legionnaires' disease cases that were determined to be definitely health care-associated, 80 percent were associated with long-term care facilities, 18 percent with hospitals and 2 percent with both.

Definite health care-associated Legionnaires' disease cases were reported in 72 facilities -- 15 hospitals and 57 long-term care facilities -- and included one to six cases per facility. Almost 90 percent of these definite cases occurred in patients 60 or older.

Of the 468 possible health care-associated cases, 49 percent were thought to be associated with hospitals, 26 percent with clinics, 13 percent with long-term care facilities, 3 percent with other settings such as outpatient laboratories, and 9 percent with more than one setting.

The MMWR report's authors said preventing the first case of Legionnaires' disease from arising in any health care facility should be the goal, and that is best achieved by establishing and maintaining an effective water management program. To this end, the CDC and its partners have created a best practices guide(www.cdc.gov) for these facilities to use.

In general, the CDC said the principles of effective water management include maintaining water temperatures that are not conducive to Legionella growth; preventing water stagnation; ensuring adequate disinfection; and maintaining equipment to prevent scale, corrosion and biofilm growth, which provide a habitat and nutrients for Legionella.

"Safe water at a health care facility might not be on a physician's mind, but it's an essential element of health care quality," said Nancy Messonnier, M.D., director of the CDC's National Center for Immunization and Respiratory Diseases, in the agency's release. "Having a water management program that focuses on keeping facility water safe can help prevent Legionnaires' disease."

In related news, CMS released a survey and certification memo(www.cms.gov) on June 2 that requires health care facilities to develop and adhere to policies and procedures to reduce the risk of disseminating Legionella and other waterborne pathogens.

According to the CDC, health care professionals play a critical role in preventing and responding to Legionnaires' disease by rapidly identifying and reporting cases.

Unfortunately, Legionnaires' disease is clinically indistinguishable from other causes of pneumonia. But failing to diagnose a health care-associated case could result in a missed opportunity to prevent subsequent cases.

Therefore, "Legionella should be considered as a cause of health care-associated pneumonia, especially for groups at increased risk, when other facility-related cases have been identified, or when changes in water parameters might lead to increased risk for Legionnaires' disease," the MMWR report advised.

The preferred diagnostic procedure for Legionnaires' disease is to concurrently obtain a lower respiratory sputum sample for culture and perform a Legionella urinary antigen test.

The CDC said ideally, sputum should be obtained before antibiotics are administered and shouldn't be rejected based on specimen quality (e.g., lack of polymorphonuclear leukocytes or contamination with other bacteria), because sputa produced by patients with Legionnaires' disease might not be purulent, and contaminating bacteria will not negatively affect isolation of Legionella on selective media.

"This report demonstrates that Legionnaires' disease continues to result from exposures to health care facility water systems," said the MMWR report. "The high case fatality rate of health care-associated Legionnaires' disease underscores the need for effective prevention and response programs.

"Implementation and maintenance of water management programs, combined with rapid case identification and investigation, could reduce the number of health care-associated Legionnaires' disease cases."

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