The new Corona Virus(COVID-19) with intense virulence, that be scared by people, has been suppressed by world wide vaccination.

As a result, the virus changed to be weaker than the previous strains, and they has started to get a new strategy to live with human-being.

This is a typical way for virus to survive with human, not a special story.

However, the number of vivctim was tragedy.

More than 30 thousand persons in Japan, more than 5 million persons in the world was historical unprecedented disaster.

In addition, this disaster is not finished.

Nevertheless, I think it would be a good idea to summarize this new coronavirus disaster as a break from the rest of the world.

I am thinking about it.

Back to the board.

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I heard that the people who don't stop using masks is a social problem now.

In my case, I didn't use a mask when I was walking alone, even while Alpha strains and Beta stock were raging in the world.

When I was alone in my room, of course, I didn't use it.

When I know that there are some person who think to use a mask when they are alone in the room, I was really surprised. (my wife said that it was a lie or a demagogue)

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The effect of masks are deceasing the risk of infection by reducing the "exposure" to virtues from droplet at close range.

The infection risk is decided by a simple multiplication of f (1) the virulence of the virus strain, (2) the amount of droplets from others (= attenuation of droplets by masks x distance from others x time spent with others), and (3) the radio of number of people infected.

Therefore, now (1)virulence is going down, (3)the ratio is also going down, so, the advice of "No mask, no problem" under the keep social distance, is a natural result.

Of course, using mask is a significant from the viewpoint of "0.001 is bigger than 0.0001", however, even if it loaded another risk (Heat stroke, etc.), it should be nonsense.

For this two years, the both risk are almost equal. however, now the balance is collapsed.

Now heat shocks are risker than the infections.

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I have watched this COVID-19 disaster from the beginning, as "Math." and "Probability".

According to the above "summarization", I think that one of them might be "few people is watching disaster from the viewpoint of mathematics and statics".