During the past two weeks, a couple dozen residents of the Quincy Veterans home in Illinois have contracted Legionnaire’s disease and four have died. During this same period, six inmates at California’s San Quentin prison have been diagnosed with the infection, and several dozen more with suggestive symptoms are under observation.
These follow a significant outbreak in the Queens section of New York City earlier this summer, which sickened more than 120 people and killed 12. Officials there identified a hotel cooling tower as the source of that outbreak. Contaminated water is likely to be the cause of the recent Illinois and California cases as well.
Although they receive little attention, outbreaks of Legionnaire’s disease, which is caused by a bacterium called Legionella, are not uncommon. Nationally, reported cases more than quadrupled, to more than 4,500, between 2001 and 2013. The fatality rate is 5 to 30 percent.
Legionnaires’ disease is preventable, so why do infections and deaths continue to occur? The answer lies within what might seem the unlikeliest of places — the CDC itself, which clings to flawed, ineffective policies.
Legionella was originally identified after an outbreak at an American Legion Convention in a Philadelphia hotel in 1976 that killed 34 and sickened 221. The bacterium lurks at low levels in natural fresh water sources (such as rivers, lakes and streams) in virtually every part the world, most often with little impact on humans. It becomes hazardous when it survives municipal water treatments and subsequently contaminates and grows in man-made building water systems such as hot tubs, decorative fountains, shower heads and cooling towers. Left undetected in these locations, it can multiply to high concentrations. People become sickened after inhaling contaminated aerosol droplets generated from these sources. Unlike most other pneumonias caused by microorganisms, this disease is not transmitted person-to-person; it is purely of environmental origin.
The only way to determine whether a water source is a high-risk Legionella-contaminated system is to take samples of the water to see whether the bacteria grow in a simple and inexpensive culture test in a laboratory. Logic would seem to dictate, therefore, that possible sources of Legionella should be monitored for the bacteria.
But that logic has eluded public health officials at the CDC’s National Center for Immunization and Respiratory Diseases (NCIRD), which has the responsibility for Legionnaires’ disease prevention. Its recommendations for prevention are predominantly focused on what might termed a disease surveillance strategy — a reactive process that relies on screening for disease after cases are detected, at which time a response is quickly undertaken to prevent further infections. Although this strategy works well for person-to-person transmissible diseases where the source of the disease is another infected individual, it is not well suited to situations in which the source of disease is in the environment.
Former Assistant U.S. Surgeon General Dr. J. Donald Millar, who used the disease surveillance approach as the head of CDC’s hugely successful Smallpox Eradication Program, has long been critical of CDC’s approach to Legionnaire’s disease. In 1997 he warned that disease surveillance was being misapplied to the prevention of Legionnaires’ disease because it is not transmitted from person to person but is contracted solely by exposure to bacteria-contaminated aqueous sources. For such diseases of environmental origin, proactive environmental surveillance, rather than reactive disease surveillance, is the appropriate prevention strategy.
Others have echoed Millar’s views, but for decades CDC’s position has remained unchanged.
A closer look at CDC policy over the years reveals the ways that a reactive approach is illogical and ineffective. A recurring theme is that CDC discourages environmental testing until an outbreak occurs. At that point, however, CDC demands testing to demonstrate that all evidence of Legionella is gone for up to a year after the outbreak. Inexplicably, CDC’s current recommendation is still that “an epidemiological association with a probable source should be established before intervention methods, such as disinfection, are undertaken” [emphasis added].
This contradiction — environmental surveillance not indicated before an outbreak, but required afterwards — in effect uses people as “canaries in the coal mine” to detect high-risk water sources. The result is frequent outbreaks such as those in New York City and San Quentin.
CDC claims that a reason for not performing environmental surveillance is that Legionella test results are uninterpretable in the absence of disease because the concentration of Legionella in a water sample required to cause disease is not fully understood. But Dr. David Krause, the former State Toxicologist for the State of Florida, dismisses this claim: “one does not need to know the concentration of Legionella required to cause disease to prevent it, one just needs to know if amplification is being controlled in the system and a simple periodic Legionella laboratory culture test can provide an answer.” Dr. Krause added that “useful guidance to help building operators interpret Legionella concentrations in water samples has been published for over 20 years by a laboratory in the private sector and have [sic] long been cited in the Occupational Safety and Health Organization (OSHA) Technical Manual.”
Dr. W. Dana Flanders, Professor of Epidemiology and Biostatistics at Emory University, has also been highly critical of CDC’s approach, “I am concerned CDC seems to be discouraging environmental Legionella testing based on flawed assumptions … when I looked more closely at references they use to support their position, I found that some of them instead actually supported the opposite position concerning benefits of environmental testing.” The problem, Dr. Flanders explained, is, “When CDC discourages proactive, routine environmental testing, the result is that hazardous sources in building settings with high counts may persist and go unrecognized until after an association with disease.”
CDC’s posture is puzzling. The number of cases since Legionnaires’ disease was discovered is staggering – on the order of 900,000, and the number of reported cases continues to increase each year. The yearly costs for hospitalizing Legionnaires’ disease patients exceed $400 million, and yet CDC still recommends through their website and scientific publications that concerned parties wait for an outbreak before monitoring and disinfecting building water sources.
Perhaps in CDC’s adherence to this approach we are seeing a syndrome that is common among bureaucrats: unwillingness to admit that they’ve been wrong. Innocent victims are paying the price.
Henry I. Miller, a physician and molecular biologist, is the Robert Wesson Fellow in Scientific Philosophy and Public Policy at Stanford University’s Hoover Institution; he was previously a Research Fellow at the NIH and the founding director of the FDA’s Office of Biotechnology.