Thinking about the current “shelter-in-place” measures and wonder what the impact will be to the spread of other diseases.
Let’s say we had a worldwide 100% lockdown. Everyone stays in self-quarantine. If it went on for long enough, say, a month, would it completely wipe out things like the flu and the cold as no one would be able to spread them anymore?
Obviously, this is not even remotely feasible. I’m not asking about that, just what the impact would be.
The quarantine would have to include animals as well. Influenza has several animal reservoirs.
While not an epidemiologist, Randall Munroe addressed this in his book “What if?” in regards to the common cold. The answer is yes, it seems possible that we could eradicate the rhinovirus ie the common cold, by isolating people.
The flu would be harder, due to its spread through animals and its ability to shift and mutate so that it can spread across species. We’d have to quarantine more than just people and domestic animals, and I am not sure how we would manage that.
Randall Munroe (xkcd) addressed this question in his book What If?: Serious Scientific Answers to Absurd Hypothetical Question. Most of the the chapter is included in the Google ebook, although the whole book is worth paying for.
He says that in theory, you might be able to wipe out the common cold, although it would take years, not a month. If everyone had healthy immune systems, you might be able to eradicate it in only a couple of weeks. But for those with compromised systems, the virus could remain for months. And for transplant patients whose immune system is being actively suppressed, it could take years, or never. All it would take is one person who still had the virus for it to spread again once quarantine ended.
Even if everyone had a healthy immune system, it would likely take longer than a month because you generally can’t quarantine individuals, only households.
One member of the household gets exposed to a cold just before quarantine starts. Everyone’s trying their best to have good hygiene, but of course we’re not perfect, so maybe a week later they’re at peak viral load and another member of the household is exposed and gets infected. Repeat.
My wife and I have two kids and when any one of us gets a cold it often takes over a month before we’re all through it. And there are plenty of bigger families than that.
You might also be able to do it with a less-strict but longer quarantine. Ideally, you’d want each sick person (or household) to transmit it to no other persons (or households), in which case it goes away after only one cycle. But as long as you can arrange it that each person (or household) transmits it to, on average, less than one other, the incidence of the virus will decrease over time, and eventually disappear.