Legionella Bacteria Concerns Grow as Schools Reopen


In a nutshell…
COVID-19, building closures, and stagnant water can form an unfortunate “trifecta” when it comes toLegionellabacteria and other microorganism growth in building water systems. This article highlights recent reports ofLegionelladetections in school water systems and steps to safely reopen school buildings to protect students, faculty, staff, and visitors.

Werecently wroteabout risks of exposure toLegionella細菌生長的建築水係統fully or partially closed workplaces as a result of coronavirus (COVID-19). Before the pandemic, these bacteria sickened and killed more people in the United States than any other reported drinking water-related illness. Thousands of school buildings across the nation, ranging from elementary school classrooms to college dorms, have also been shuttered for many months. And with Labor Day just behind us, millions of students have already started returning to school.

Building closures and reduced occupancy conditions will affect all building environmental systems. These must be maintained to protect building occupants. Extended property closures can lead to unsafe building water system conditions, such asrecently reportedfindings ofLegionellain several schools inPennsylvaniaandOhio. There is concern that school and public health officials lack plans or effective guidance for addressing the effects of prolonged shutdowns generally, or specifically regardingLegionellarisk.

Legionella, Stagnant Water, and School Buildings

Legionellabacteria are common in warm, freshwater environments like lakes and streams. They are also known to grow readily and can be commonly found in building water systems, particularly in the microbial growth on pipe walls calledbiofilms. When a school’s water system is not in use, stagnant water fills the pipes, tanks, and other water features.Legionellaalong with other pathogenic microorganisms like mycobacterium can thrive in stagnant water, particularly in hot water heaters and pipes that have cooled to temperatures in theLegionellagrowth range of 77–108°F (25–42°C). This is because the chlorine or chloraminedisinfectant residual, typically provided in treated water from a local drinking water utility, has decayed due to reaction with organic and inorganic compounds or disappeared entirely. The extent of stagnation and risk ofLegionellacan vary between school buildings, even on the same campus.

Legionellaand Legionnaires’ Disease

Inhaling, but not drinking, water droplets (aerosols) containingLegionellabacteria can causeLegionnaires’ disease, which is a serious and potentially deadly form of pneumonia. Most healthy students and other persons exposed toLegionellafrom school building water systems will not get sick. Those who do are likely to get Pontiac fever, a flu-like illness that is usually self-limiting. Students, teachers, and faculty at increased risk of Legionnaires’ disease include those with compromised immune systems or a chronic lung disease. As we noted in our May 15, 2020, article, “The threat from Legionnaires’ disease may be compounded because its victims tend to share similar symptoms as coronavirus patients, including cough, chills, and fever, makingmisdiagnosis a possibility.”

LegionellaTesting in School Buildings

There are no national regulations or requirements forLegionellatesting in public schools. Similar tolead testing in school drinking water,Legionellatesting and reporting programs are largely voluntary or tied to specific school systems. Although health authorities are required to report cases of illness caused byLegionellato the U.S. Centers for Disease Control and Prevention (CDC), there are no requirements to test and report the presence of the bacteria. A recentNew York Timesarticleon this topic reported that somepreventivesteps schools may take to limit coronavirus infection risk could inadvertently add toLegionellaconcerns. For example, many schools are turning off drinking fountains and some bathroom sinks to ensure social distancing. However, that practice can create reservoirs for bacteria and can contribute to lead levels in drinking water fountains.Shower headslike those found in closed locker rooms are common places to findLegionellaand other microbes and where inhalation of aerosols is most likely.

Of course, many school systems do not have the budget to test forLegionella. But even those schools that have tested recently and had positive test results may have also been positive forLegionella(and not know it) before the pandemic and closures, so theLegionellarisk may not have changed. Moreover, school systems that do test often lack the knowledge and authoritative guidance on how to respond.

Guidance and Steps for Reopening School Buildings

Utilities are responsible for delivering disinfected drinking water to school buildings,1but school systems must ensure the safety of water within their buildings. CDC has issuedGuidance for Reopening Buildings After Prolonged Shutdown or Reduced Operation, including schools. It outlines eight steps to take before and during reopening a building to reduce risk fromLegionellaand mold. These steps include ensuring water heaters are properly maintained and the temperature set to at least 140 °F (60 °C); flushing the water system throughallpoints of use (e.g., taps, showers); and regularly checking residual disinfectant levels. CDC recommends wearing a half-face air-purifying respirator equipped with an N95 filter or an N95 filtering mask in enclosed spaces where aerosol generation is likely. CDC also warns that people at increased risk of developing Legionnaires’ disease should consult with a medical provider before participating in activities that may generate aerosols.

Anewly released paper, “Preparing for COVID‐19’s Effect onLegionellaand Building Water Systems,” in theJournal of the American Water Works Associationalso offers guidance on starting a building water system after a prolonged closure. That 11-step guidance includes recommendations to test forLegionellato evaluate the effectiveness of building start-up procedures. It emphasizes waiting 48 hoursafterfinal flushing to collect samples for testing; testing immediately after flushing will likely just result in a negative test. If appropriate testing reveals widespread or high levels ofLegionellain the water system, corrective actions may be needed. In addition to system flushing, two widely recommended measures are “shock chlorination” and “thermal shock” disinfection of the building water system. Some of the affected Pennsylvania school officials opted for thermal shock and flushing while at least one Ohio school sent a high level of chlorine solution through their building water system in addition to flushing. Because confirmation of tests forLegionellacan take weeks, many of those schools in Ohio and Pennsylvania had to rely solely on operational risk-reduction precautions only prior to opening their doors to students.

Final Thoughts

As our students and teachers head back to school, we must be mindful of more than masking with social distancing and COVID-19; we must also remain vigilant about the risk ofLegionellain under-used school building water systems. By thinking through and implementing procedures to address stagnant water conditionsnow, school officials and building operators can help protect students, teachers, staff, and parents as formerly closed or partially closed school buildings continue to reopen into the fall. School and public health officials should consider CDC’s guidance and at the very least flush the entire building water system (hot and cold) before opening a school building after any prolonged shutdown.

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1Unless the school provides its own treated and disinfected drinking water as a U.S. Environmental Protection Agency-regulated“non-transient, non-community” drinking water system.

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