Probability of getting Covid19 is 200 of Flu

Based on this article we can say that it should be around 10%, i.e. 1 in 10, not 1 in 1000.
But this is for the whole year, and for every ages.
We are only interested in the chance of getting flu in 1 month, for 18-40 year olds, in order to compare with Covid-19.

18 - 40 years make up half of the population so the chance of getting flu is only 5% or 1 in 20.
But the time taken is only 1 month, which is only 1/12 of the year. To simplify matters, the chance of getting flu in one month is taken as 1 in 10, so the total chance of getting flu in one month is 1 in 200.

For Covid 19, it is 100% or 1. It is a certainty that you will get it if you don't take any precaution at all, like what you are doing with flu, except that for flu, many people can take the vaccine, and a lot of people have built-in immunity.


https://www.quora.com/What-are-the-odds-of-getting-the-flu-if-you-dont-get-the-vaccine

Omar Stradella, works at Genzyme

Answered Apr 23, 2019

Let’s do the math. The CDC estimates[1] that there were about 49,000,000 cases in 2017–2018. The US population in 2018 was estimated[2] to be about 327,000,000 with 22.6% under 18 years old. The vaccination rate was 37.1% for adults[3] and 57.9% for children[4].

327,000,000 people = 253,098,000 adults + 73,902,000 children

Number of unvaccinated people = 253,098,000 * 0.629 + 73,902,000 * 0.421 = 190,311,384. Assuming that only unvaccinated people got the flu that means that 49,000,000/190,311,384*100 ~= 26%. So the odds of getting the flu if you have not been vaccinated are about 1 in 4. Now, since the vaccine was only about 40% effective, the odds are lower than that. If calculate using the whole US population, the odds would be 49,000,000/327,000,000*100 ~= 15%. The true odds would then be somewhere between 1 in 7 to 1 in 4. Another assumption is that people only gets the flu once a year.

Footnotes

[1] Estimated Influenza Illnesses, Medical visits, Hospitalizations, and Deaths in the United States - 2017-2018 influenza season

[2] U.S. Census Bureau QuickFacts: UNITED STATES

[3] Estimates of Influenza Vaccination Coverage among Adults-United States, 2017-18 Flu Season

[4] Estimates of Flu Vaccination Coverage among Children - United States, 2017-18 Flu Season

https://stats.oecd.org/Index.aspx?DataSetCode=RPOP#
In 2012:
Above 40 years old, 146 million
All ages, 312 million

We should just estimate it to be 50%, i.e. 1 in 2