Two classical liberal notes on epidemic response.

The response to an epidemic of an infectious disease is a genuine public good.

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When economists use the term "public good," they do not use it in the same way that non-economists (and most politicians) generally do. They most emphatically DO NOT mean that the thing at hand is generically good for the public.

In this case it certainly is good for the public, but being generically good for the public is not a sufficient condition for a thing to be a public good in the economic sense. To qualify as a public good, a good must also not be easily excludeable from public enjoyment.

Bread is good for the public, but it's not a public good, because--as we all know--it's pretty easy to exclude people from eating it. To qualify for public good status in its specialised, technical sense, the good at hand must be something that you can't lock away in a drawer.

If it's possible to contain an epidemic through quarantines and other measures, then it is necessarily the case that everyone in the world benefits from these actions, with no exceptions. To the extent that a quarantine works, no one is excluded from the benefits of not getting COVID-19. (Consider that any state trying to exclude its enemies from the benefits of not getting sick--via germ warfare--would commit a blatant crime against humanity. It is unlikely that any state would find this reputational risk worthwhile.)

In its status as a public good, an epidemic response is very similar to national defence, and it therefore has a place in the small basket of state-provided goods that even classical liberals have always assented to.

This one is somewhat more contentious, because--unlike economists with the term "public good"--public health officials have heartily embraced the idea that anything that makes anyone healthier is a matter of public health.

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It did not always used to be this way, and perhaps it should not be this way. It did not always used to be the case that the term public health encompassed personal behavioural choices that affect primarily oneself, such as smoking, not exercising, or eating badly or too much.

Each of these is certainly a health problem, but the harms fall chiefly on the person doing them, not on bystanders. While each is commonly talked about as a matter of public health, it would be much more accurate to say that these are matters of personal health. Yes, they have been repeated on a massive scale, but they can be effectively "contained," if you will, simply by not imitating bad health behaviours. A similar dynamic does not apply for an infectious disease, which can be very difficult to avoid contracting even with good individual behaviour.

In the response to an easily contagious virus, we have a matter of public health in its older, narrower definition, one that involves effectively all of us as bystanders--as individuals subject, arbitrarily, to the full effects of the unwitting behaviours of others. In cases like these, classical liberal accounts of government action generally support the idea that public health interventions ought to occur. The details are a matter for medical science to figure out, and it should go without saying that much balancing and judgement will be necessary along the way to preserve a decent quality of life for all involved, to the extent that it is possible. But I'd simply say that while a minarchist libertarian accepts only a few types of state action as legitimate, this is one of those types.

I am not sure I can even imagine an anarchist attempting to respond convincingly to such a situation. I have nothing to say on that score, but maybe some of you might.