Growth of Legionella during COVID-19 lockdown stagnation

While “avoiding stagnation” has been the mantra of many building water quality experts, the foundational support for how this terminology is used in peer-reviewed publications and building water management guidelines is not overly convincing. With COVID-19 lockdowns and subsequent reopening, the concern that extended stagnation will trigger increased incidence (or even an epidemic) of legionellosis has been widely raised in the news and social media. Here, we provide a perspective on four simple questions to a complex topic, with hope that it encourages a broader dialogue and more critical assessment of assumptions and communication strategies surrounding stagnation and Legionella growth.