Now, I'll take some of my time to address the topic of "cherry-picking" data. I'll start with some general principles and in a later post address the specifics of the flu and Covid-19 statistics that I posted.
Others have already posted, as have I, that when you're attempting to make a comparison of two different things with some similar characteristics and some differences, to gather data and compare their difference in some aspect, you want to minimize the variables by making the the conditions for comparison as identical as you can for the items being compared. It's common sense as well as standard practice in making comparisons for the obvious reason that changing the conditions for one item will skew the results relative to the other. Others have used analogy to illustrate the principle and I'll have a go at it as well.
Let's take two different devices which receive broadcasts transmitted thru the air, a TV and a portable radio. You want to determine how many stations each will receive. Your TV is connected to your HDTV antenna and your portable radio has a built-in AM/FM antenna (one of several differences between the devices) and you're testing them as you use them to receive transmissions each day. You put them side by side in your living room, at the same time, and record the number of stations each receives clearly. You now have some data on the number of stations each receives under those specific conditions at that time and place. You have one valid data set relative to those conditions.
Your friend objects and says that it isn't a valid comparison because you have "cherry-picked" the location. Your television is typically stationary and viewed only at your home in the city, whereas the portable radio is typically mobile and could be used in a variety of locations outside of your home, he says. So, he borrows the radio and records data in the mountains, the valley, the desert, and other locations and gives you his data record. Thanks, but you didn't have the TV to compare under those conditions, you say. Sorry, I didn't have a generator to power the TV, he replies. You gratefully acknowledge the additional data, but you can't make any valid comparisons from it because there was no data for the TV under those same conditions. It's additional data, but it only tells you how one of the items you were looking to compare actually functioned under those different conditions. Seeing how the portable radio varied in reception is interesting, but it gives you no useful comparison data.
We have data on influenza from before the 1918 pandemic until now. It's useful for comparing and evaluating how the flu changes from one season to the next, how it is evolving over time, the variations in different influenza virus types and subclasses and their effects at different times in various places. It's useful data for comparing specific flu viruses or seasons to others due to the evolving nature of the virus and its multitude of variations over time.
COVID-19 is a different virus which shares some similar characteristics with the flu, like the modes of transmission and the fact they both mutate and evolve for instance. There are also differences between them, like the rates of transmission and mortality. Another major difference is that COVID-19 has only been circulating in the population for the past two years, which means that time period is all that is available with which to compare.
