Thursday, April 22, 2021

Can you catch Covid from an empty washroom?

by George J. Dance

Can you actually catch Covid from being alone in a public washroom? It could happen; at least, that is the newest scare story making the rounds in Canada. Here is a sample, which made it onto our national news: 

Don't linger after you flush: Public toilets may spread COVID-19 aerosols, study finds | CTV News - Nicole Bogart:

April 20, 2021 - "Though a public washroom isn’t typically the kind of place you want to spend a lot of time in, new research exploring COVID-19 transmission suggests you may not want to linger after flushing a public toilet. A team of scientists from Florida Atlantic University's College of Engineering and Computer Science conducted a series of tests investigating the spread of microbe-containing aerosol droplets generated from flushing a toilet or a urinal in a public restroom. Using a particle counter to measure the size and number of droplets generated upon flushing, researchers found that the droplets were detected at heights of up to five feet (1.5 metres) for 20 seconds or longer after flushing. Worse yet, researchers detected a smaller number of droplets in the air even when the toilet was flushed with a closed lid, suggesting that aerosol droplets can escape through small gaps between the cover and the seat.

"After about three hours of tests involving more than 100 flushes, we found a substantial increase in the measured aerosol levels in the ambient environment with the total number of droplets generated in each flushing test ranging up to the tens of thousands," study co-author Siddhartha Verma said in a press release issued Tuesday. Both the toilet and urinal generated large quantities of droplets smaller than three micrometers in size, posing a significant transmission risk if they contain infectious microorganisms. Due to their small size, these droplets can remain suspended for a long time."

Read more:

That is scary, especially for senior citizens such as myself. Not only are we more vulnerable to severe disease or even death from Covid, but we are also more likely, when we go to the mall, to have to use the public washroom. I cannot remember the last time that I went to the local mall and did not have to, What do I need to do to to protect myself from this new threat? Should I simply stop going (in either sense)? Should I start wearing adult diapers? Or is it enough to just never flush? 

Or is it even a risk worth worrying about? How likely is there to be Covid in the toilet? I am no virologist, so I can only try to estimate the risk; but I cannot see much of one. 

First, there is no risk to me of catching Covid if I already have it; and there is no way I could be depositing Covid in the toilet unless I already had it. Therefore the only danger to me is if an infected person had previously flushed. How long previously? We are told that the aerosols can be present for "a long time," but the only time actually given is "20 seconds or more." How much more? I actually doubt that it is more than a minute; if the aerosols persisted for at least 60 seconds, I suspect that the researchers would have used that higher figure instead.

But assuming the little devils last long enough in water to infect the next user: how could they get into it in the first place? They would have to be in feces and urine. They certainly couldn't reproduce). Before that, they had to have passed through someone's stomach; not the most hospitable environment for living things. Even if a few made it through, they could not have been reproducing at the same time; so the number out would always be smaller than the number going in. 

And how would they get in someone's stomach in the first place? Sars-Cov-2, remember, is a respiratory virus; and respiratory viruses do not live and reproduce in the stomach. There could be stray virus on some food that one ate, but normal sanitary procedures should eliminate that possibility. Without evidence to the contrary, I doubt that the coronavirus survives being cooked. 

Of course, I am simply using reason here; and reason is a weak tool, in the lack of sufficient data to form true premises. So let us look for more facts. 

The article does say that scientists have discovered "small numbers of viruses in urine and stool samples." That is good to learn; a small amount of virus may survive a trip in feces as well as in water (though it may not actually be live virus; not enough information is given). But, again, it cannot reproduce there. So we are talking about a small number of viruses in urine or feces, of which a smaller number transfer to the toilet water, of which an even smaller number are ejected into the air in the form of aerosols. The all-important question, is: are these small amounts enough to infect someone in the few minutes it takes to use a washroom? Just how much of the virus is there in those aerosols? Surprisingly, the study does not say; because, it turns out, the scientists did not look for coronavirus:       

However, researchers did not analyze the aerosol droplets found in the restroom. Therefore, it is unclear whether COVID-19 aerosols were found in the sampling.

Wait, what? The researchers did not look for Covid aerosols. Therefore they did not find any. It is unclear whether there were any; but it is certainly clear enough that none were found. 

And that is enough to form an opinion on the article. The study on which it was based seems sound enough, but that study proved only that there are aerosols in washrooms; which may be a problem in public schools, where the children have to use the washroom en masse at recess. But the idea behind the news report, that anyone whomsoever is at risk of contacting Covid and possibly dying just from using an otherwise empty washroom, sounds full of – well, of whatever toilets get full of. 

Read study here:

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