Covid-19: How to Keep Buildings Safe | Hopkins Bloomberg Public Health Magazine

The SARS-CoV-2 virus can threaten you when it’s lingering in the air—and even when it’s not there at all.

A good ventilation system can help clear the air and reduce the risk of transmission, though masks and social distancing are still important, says Ana María Rule, PhD ’05, MHS ’98, an Environmental Health and Engineering assistant professor. Yet by causing buildings like dorms and hotels to be left empty or under-occupied for months, the coronavirus has spawned a very different threat: Legionella bacteria, say EHE’s Professor Kellogg Schwab, PhD, MSPH; assistant scientist Natalie Exum, PhD ’16, MS; and PhD student Monica Lee.

Ventilation

Most buildings don’t need HEPA (high-efficiency particulate air) filters. MERV-13+ (minimum efficiency reporting value) filters are adequate.

Ventilation systems must keep air moving. At least 4 air changes per hour in a room is recommended.

Cranking the building heat won’t work. Virus-killing air temperatures would have to reach about 70º C (158º F).

Mixing in outside air is important. It may not be energy efficient, but safety is the priority.

Water System

Shower head aerators can disperse Legionella into the air.

Biofilm, a gelatinous coating, can develop in stagnant water in pipes and may contain Legionella.

Low building occupancy reduces water flow in dorms, hotels, schools, and gyms, increasing risk for Legionella growth.

Breathing aerosols that bear Legionella bacteria presents a significant risk—especially for older people and the immunocompromised.

Legions of Bacteria

Legionella bacteria:

Grow in stagnant water in pipes that lack sufficient disinfectants
Annually lead to 52,000+ U.S. cases of Legionnaires’ disease, a lung infection

Solutions

Building managers should flush water pipes and monitor for Legionella.
Your hotel’s had low occupancy? Consider not taking a shower.
Back from vacation? Run showers and sink faucets for 5 minutes to flush out the system.