why do you presume it targets the older or infirm?
Spanish flu didn’t
Spanish flue had a higher death rate amongst the fittest of people rather than the elderly, the reason being the imune system in fit people went into overdrive (a strong over reaction) and this shut the body organs down,its common knowledge that the virus we are dealing with today is more ruthles on the middle aged and those with lung disorders such as a history of smoking or indeed a low imune system such as HIV or even being a diabetic will put you more at risk of dying