Tuesday, May 19, 2020

Toilet Aerosols A Primary Coronavirus Contagion Vector


According to the U.S. Centers for Disease Control and Prevention (CDC), the COVID-19 virus spreads from person-to-person among close contacts and occurs mainly via respiratory droplets produced when an infected person coughs or sneezes. These droplets can land in the mouths or noses of nearby people or possibly be inhaled directly into the lungs. It might be possible for a person to get the virus by touching a contaminated surface or object and then touching their own mouth, nose, or eyes.
 
How can the coronavirus spread through bathroom pipes? Experts are investigating in Hong Kong” A https://www.cnn.com/2020/02/12/asia/hong-kong-coronavirus-pipes-intl-hnk/index.html

waterandhealth |  According to the article,2 two residents living on different floors of a high-rise apartment tower called Hong Mei House had been infected with coronavirus according to Hong Kong health officials. The first to be infected was a 75-year-old man. About 10 days later, a 62-year-old woman in the same building became infected. That woman’s son and daughter-in-law who share the apartment were later diagnosed with COVID-19.  

In the tower, the first two persons with coronavirus lived 10 floors apart, but were located in the same vertical block of apartments. For this reason, health authorities conducted an initial investigation and evacuated all residents living directly above and below each other in block seven across all 30 floors because their toilet and vent pipes were all connected (see figure).

Scary Reminder of the 2003 SARS Outbreak

The possibility of the coronavirus being transmitted through building sewage pipes immediately drew comparisons to the 2003 SARS (severe acute respiratory syndrome) coronavirus outbreak, where this was discovered to be a major source of transmission. At the Amoy Gardens housing estate, also in Hong Kong, more than 300 infections and 42 deaths occurred after poorly-designed plumbing allowed the SARS virus to spread throughout the building complex. As a result, following a 24-hour medical lock-down, the residents were moved to confinement camps for 10 days as doctors, clinicians, sewage experts and engineers investigated.  

How Could Bathroom Sewage Pipes Spread Coronavirus?

The COVID-19 virus could have spread through the Hong Mei House through close human contact or the shared use of elevator buttons. But because the two first patients lived above and below one another in the tower, and because an initial inspection found that a vent pipe had been disconnected from the bathroom’s waste (soil) pipe, the building was partially evacuated. Although a full investigation is ongoing, based on the initial investigation, health officials declared the Hong Mei House’s sewage pipe system to be safe. 

Preliminary studies of the COVID-19 virus have suggested it is present in fecal matter, though it is still unclear whether the coronavirus could be transmitted and infect others by some type of fecal-oral route (via exposure from hands to nasal passages and eyes not through ingestion). As can be seen in the figure, toilets (as well as sinks and floor drains) have a “U-“ or “P-shaped” pipe that prevents sewer gases from entering the home and that allows wastewater and odors to escape. To work properly, the sharply curved pipe, also known as a “trap,” needs to hold water in its bend. These connect to a soil pipe, which washes the waste down and away from the toilet, sink, or drain. The soil pipe also needs to be connected to a vent pipe to remove sewer gases and odors—usually through roof vents. The vent pipe also ensures that wastewater keeps flowing freely. One local microbiologist suggested at a press conference that the improperly sealed vent pipe “could have resulted in a virus transmission, by carrying infected feces into the building’s ventilation system and blowing it into people’s bathrooms”.