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Sunday, 24 May 2020

Day 69 of self-isolation - The Masked Hamsters

The masked hamsters

Fox News have reported an important test done on the question of masking and Covid-19
For this, they used hamsters. Hamsters can also catch Covid-19, and  it's easier to use hamsters for a potentially lethal test, than humans.

So here's what they did.

They set up two cages of hamsters. One cage with infected hamsters, and  one cage uninfected. They set up a fan to blow air from the infected  cage, to the uninfected.
Covid-19 is very infections, so they  found that at the end of the test, 2/3 of the clean hamsters, were now  infected. That is just from breathing in the air that the infected  hamsters had breathed out.

The next test, used more hamsters.

They put masking over the clean hamsters cage. At the end of the test,  33% of the hamsters had become infected. So wearing a mask halved the infection rate. Also, the newly infected hamsters had a lower viral  load. Less viruses. Meaning they weren't so badly infected.

The third test used more hamsters

The put masking over the infected hamsters cage. At the end of the test, 15% of the clean hamsters were infected.

What does this show?

It shows that for hamsters, masking infected hamsters reduces the infection rate to a quarter that you get without masking. Masking uninfected hamsters reduces the infection rate to a half that you get without masking.

It would be very unethical to try the same experiment with humans, but we can expect that the results would be similar. And we can expect that if both the infected, and the uninfected hamsters were masked, the infection rate would be even less than 15%.

The counter-attack on the coronavirus (until we have a vaccine) is to reduce the transmission rate (R0) between people. The transmission rate of Covid-19 is about 3, meaning that each infected person, infects an average of three people. That's why it spreads so fast.

If the R0 could be reduced to a quarter of that, down to 0.75, then the virus will die out. We're getting that effect via the "stay home, wash hands, social distance" system.

But suppose everyone would be persuaded to wear masks. We would get the R0 down to the necessary level, without the economic damage of the lock down.

And that is possible - in South Korea, Japan and Taiwan, it has been standard for a long time, if a person has a cold or flu or similar symptoms, to wear a mask in public. Why?

When you sneeze, you blast out a vortex of droplets (containing the virus) for 23 to 26 feet. Coughing reaches 19 feet, and just breathing and talking, 7 feet (hence the six foot rule). Some of those droplets are large, and fall onto nearby surfaces, waiting for someone to touch them. Some are tiny, and stay in the air for minutes. Some droplets are so small, they evaporate quickly, leaving the virus particles floating in the air for hours.

But if you wear a mask, that interferes with the blast, and stops it reaching out. The sneeze or cough is trapped by the mask, and doesn't infect so many other people.

People in South Korea, Japan and Taiwan are patriotic, and care about their fellow citizens, and are keen to pretect them from disease. In the case of Covid-19, half the people who get infected, don't have symptoms, but are still infectious.  And those that do get symptoms, are infectious for a few days before the symptoms appear. So if you don't know that you're clear, you can't assume that you are.

So why won't this work in the USA? Why was the lock down necessary? I think it's obvious that a large number of Americans are unwilling to mask (for example, Trump is clearly unwilling), and they say so, often loudly, and pretend that this is something to do with freedom (do they also claim the right to drive while drunk?). The same might be true in the UK and other European countries, but I'm not so sure - we're a lot more patriotic than Americans.

So I think that, when the lock downs are eased in Europe, governments should strongly encourage, or even mandate, the wearing of masks in public.

Because if we were willing to endure the MAJOR inconvenience of staying home and closing so many businesses, we should be willing to put up with the very minor inconvenience of masking in public.

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