Why Do Some Buildings Have a Higher Legionella Prevalence Than Others?

Otto Schwake, PhD, Department of Civil and Environmental Engineering at Virginia Tech, lead researcher from the Flint Water Study team, explains why in Flint, Michigan, Legionella prevalence differed based on building size.

Interview Transcript (slightly modified for readability)

“It’s been pretty well-established, in a number of studies throughout the years since we’ve known about Legionella, that there are specific conditions, when we’re talking from an engineering perspective, that make a building or water system more conducive for Legionella.

Some major ones are hospitals: you have buildings that are old, tall, have unique flow conditions, and heated water. So, when we look in Flint, Michigan, for example, looking at a small house, it might have some flow problems [and] it will have heat, but it will be small [and] more than likely not as old as some hospitals which could be [potentially] decades, 70, 80, [or] 90 years old. For example, one hospital we looked at had over ten stories, [it was an] over 50-year-old building, and [had] some interesting flow conditions, including what we are assuming [were] stagnant areas, deg-leg areas, where water flow isn’t ideal or, if anything , sporadic due to rooms not being used all the time. Conditions in these larger buildings are a reason why they’ve been associated more so with Legionella contamination.”