R0 depends both on behaviors that lead to infecting others and behaviors that lead to being infected. In the case of COVID-19 these are largely the same behaviors, with the difference being that you do one while being infected and the other while being vulnerable.

All else being equal, a person who has recently been exposed to other people is more likely to be infected than a person who has recently been in isolation, and a person who has been in isolation is more likely to be vulnerable to infection because they have a lower probability of being currently infected.

By coming out of isolation for less than the time it takes from infection to an infected person becoming infectious, and then isolating for longer than it takes for an infected person to be no longer infectious, we can separate out the time periods where a person is more likely to be infected and where they are more likely to be vulnerable to infection. This would allow us to make sure that the person has a low probability of being in contact with other people for a least one of these time periods.

Concentrating behaviors that increase the chance of being infected or infecting someone else -- for example contact with other people and interspacing it with periods where such behaviors are abstained from -- should lead to a lower R0 than spreading the same behaviors evenly over time.

If someone went out today, it is better to go out today again than to go out next week because even if the person has been infected today, it will not be infectious today, but it will be infectious next week.

This is an idea, where someone who doesn't know much about it tries to game a system. Usually there are more complexities involved than the person is aware of.

  • 1
    "the time it takes for an infected person to become infectious" -- what are you measuring this from? From knowing they are infected? They may never know. Or from becoming infected? Sort of "I went out yesterday but even if I got infected then I wouldn't be contagious now so I can go out today" kind of deal? And if you want to be "lower" I have to ask "lower than what?" Describe the behavior you're comparing to. May 17, 2020 at 14:09
  • edited to make question more specific and clear May 17, 2020 at 17:12
  • 1
    I'm not seeing that. Why not say things like "1 day" and "14 days" and compare two strategies, such as "go out every 5 days" vs "go out every 10 days" or whatever. Right now it is "is A better?" where both A and the imaginary B it might be better than are not defined. May 17, 2020 at 17:56
  • also, there is a base non-zero chance of being infected on days you don't go out, if someone who lives with you is coming and going, or if you are picking up mail or packages, or ... May 17, 2020 at 17:59
  • 1
    I edited your question to improve clarity. If you think I changed the meaning of your question, you can revert my edit.
    – Carey Gregory
    May 18, 2020 at 5:03

1 Answer 1


You should go out as infrequently as possible, and only when it is truly necessary. If you need to buy food, go out and buy enough food so that you can stay inside for at least a week, preferably two. Do not go out just because you want to or because you are bored.

Within this framework, what is the argument for going out on consecutive days? That even if you were exposed on Day 1, your Day 2 trip wouldn't risk exposing anyone else? Perhaps, but if you had been contagious without knowing it on Day 1, you would still be so on Day 2, so the extra trip out is risky to those who are also out.

One way to be relatively sure you're not contagious is to stay in for 14 or more days at a time. This is easier for some people than for others. If you have a car, a large freezer, and a pantry, along with a healthy bank account, then stocking up and shopping at more than 14 day intervals is simple -- I've been doing it for 9 weeks now.

Is it safer to go out on day 1 and 2 and then not again until Day 15 or 16, than to go out on day 1, 8, 15, . . . ? Probably. But it's safer still to go out on only day 1 and 15. There's no good argument for the Day 2 trip. This is especially true if you have possible sources of infection other than going out. For example, if you live in an apartment and go to the lobby for your mail or into the hall to put garbage down the chute. If you're receiving deliveries of takeout food or online orders. If you're living with someone who is still going out to work. If you go out to your garden, and then back in again, touching a doorknob or other outdoor surface that might have been coughed on by a visitor or delivery person, and so on. In all of these cases you can get infected without going out, and every trip out is a chance for you to infect others.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.