Post #898: Quarantining your college student rationally. Or, should I lock my daughter in her room while I go grocery shopping?

Posted on November 22, 2020

This post is motivated by the need to bring my daughter back from college next week.  What I was wondering is, should we all be wearing masks in the car?  But more generally, what’s the standard protocol, quarantine-wise, for returning college students?

Seems like a fairly straightforward question.  Given that there are going to be millions of college students returning from campus to home in the next few weeks, it seems like there ought to be be some standard answer to that question.

Sure seems like it.  Ought to be.  But there ain’t.  Let me summarize what I found.

When I do the math, under the circumstances I face, the likelihood that my daughter is going to give me a COVID-19 infection is 1-in-30,000.  Over the same period, the likelihood that I would just pick one up, as an average member of the community, is 1-in-93. 

So, to answer the question in the title, it makes no sense to lock up my college-age daughter, while I continue to go grocery shopping. 

Unless that’s to protect her, from the risk of COVID-19 infection that I might be bringing home.

Want do the quick-and-dirty calculation for your own returning college student?  Based on the assumptions below (the student tests negative for COVID-19 and doesn’t pick up an infection while traveling home), the 1-in-X odds of  your student transmitting infection to you, X = 11*campus enrollment / new campus COVID cases in the last two weeks.  If they don’t have a negative COVID-19 test, then replace the factor of 11 with a factor of 3.


The advice I found on quarantining your college student seemed to depend  heavily on how prevalent COVID-19 was in the area, and the health risks present in the parental household.   Places with big current outbreaks, areas where COVID-19 was present in the schools, and articles targeting the elderly called for every possible precaution.  Others, in areas where risks were lower, less so.

And so, one way or the other, it boils down to advice offered by Dr. Fauci:  It depends. 

“It depends on where they’re coming from and what the level of infection is in the community they are in.”  “There is no right or wrong answer. It’s about the relative risk you’re willing to take,”  “It depends on the contacts in the home you’re going to. If you have an immunosuppressed person or a grandfather who’s 92 years old, the risk is great. If you’re going into a home with a healthy 45-year-old father and mother and a brother and sister in their teens, the chances of there being a problem are much less.”

Source: New York Times.

OK, I’ll take that advice.  So what’s the right answer, for me?  I started compile a list of recommended precautions.  And by the time I was done, I was beginning to see something that was a bit over-the-top.  And all of it — almost every damned bit of it — is offered without any evidence-based support whatsoever.

In short, what you can find, for advice, is basically a series of off-the-cuff suggestions that people have made, for things that seemed reasonable to them.  And, with the exception of wearing masks — where there is some empirical work behind that — with, as far as I can tell, no evidence basis whatsoever for making the recommendation.

And the available advice boils down to “do everything, to be as safe as possible”.  Neither more nor less quantitative than “Be afraid”.  And I’m old enough to recognize that as pretty crappy advice under most circumstances.  And it’s advice that basically nobody currently follows.  At least, nobody who has (e.g.) gone to the store in the last half year or so.

And so, it really boils down to your own tolerance for risk, followed by what amounts to total guesswork as to what will materially reduce your risk.  Against a backdrop of the COVID-19 risks that you are willing to tolerate, every day, as you go about with your life.

As always, with a mushy task like this, you can either flail about in a sea of what-ifs, or you can try to quantify things as best you can.  And so that’s what this posting is about.  Let’s hang some numbers on this decision and see what it looks like.

So in this posting, I am going to:

  1. Start with a laundry list of every precaution I found mentioned.
  2. Explain why I am going to do more-or-less none of that (with calculations!).
  3. Provide the detailed summary of the information I found.

If you child is coming from a place where there was a lot of COVID-19 on campus, and didn’t reduce social activities in the last week of school, and hasn’t been tested, and/or you have vulnerable people in your household, you might be well advised to take this laundry list below seriously.  If the reverse is true, you might want to do a little arithmetic yourself, and decide whether or not this laundry list of precautions adds materially to your safety.

You can chalk my decisions up to COVID fatigue if you want.  But those of you who read this blog understand that I’m a fairly cautious, fact-based guy.  And in my own circumstances, I just don’t see the benefits of taking a lot of precautions against what appears to be an absolutely miniscule risk.

The incremental risk from my daughter doesn’t even count as rounding error in my overall risk calculation.  Bottom line is that if I’m going to (e.g.) go to the grocery store to pick up a Thanksgiving turkey, I’d be an idiot to take any sort of precautions in being around my daughter.  To the contrary, I’m more of a risk to her then she is to me.

YMMV.  Details follow.

1:  Laundry list of precautions.

This is my summary of what I found in a quick Google search of the topic.  Detailed synopses of several articles are given in a later section below.

FWIW, I think it was the advice to roll down the windows of the car, periodically, that made me roll my eyes.  The second time I saw that offered.  Without attribution as to source, and with not a shred of evidence to back that up.  That’s when I realized that just about everybody offering advice on this topic was winging it, and many of them were just plagiarizing other people who were winging it.

Again, this is just a laundry-list of things I’ve seen in various news articles.

  • Students should minimize social exposure in the week before coming home.  No parties, no bars.
  • Students should get tested forCOVID-19 before returning home.
    • Or maybe get tested twice before returning home
    • Or maybe get tested before and after returning home
  • Driving your student home?
    • Wear masks in the car.
    • Keep the windows open/open them periodically
    • Keep the heat/AC on fresh air not recirculating.
  • Student traveling some other way?
    • Standard precautions (mask, distancing)
    • Launder clothing and mask immediately upon return
    • Store luggage in isolated area.
  • While home (for up to two weeks):
    • Wear masks.
    • Maintain social distancing.
    • No hugs or handshakes.
    • Separate bedroom, separate bathroom.
    • Wipe down touch surfaces.
    • Have student eat separately from everyone else, or at least eat at one end of a table, separated from everyone else.
    • Student not to socialize with friends indoors without social distancing and masks.
    • No or minimal contact between student and vulnerable individuals.

2:  What I am actually going to do.

First, I’m going to do a calculation:  How likely is it that I would be infected with COVID-19 by my daughter.  This assumes “average behavior” all around.

I’m going to skip over the details, because nobody ever cares about methodology anyway.  And get to the bottom line.  This is for a current William and Mary student who tests negative for COVID-19 just prior to returning home.

You want the real quick-and-dirty?  The only thing that would change for some other campus — assuming a negative test — would be the first two numbers:  New cases on you kid’s campus over the past two weeks, and the total number of students on that campus.  Assuming your student tested negative before returning home, and didn’t pick up a case on the way home, the relevant nubmer for your student would be:

Likelihood = 0.092 * new cases on campus in last two weeks /campus enrollment.  And then your “odds” is just 1/likelihood. 

The real-real quick-and-dirty calculation:  Odds of  your student transmitting infection to you = 11 x campus enrollment / new campus cases in the last two weeks.

Roughly 1-in-30,000.  The chance that my asymptomatic daughter, with negative COVID-19 test, will bring home a COVID-19 infection from William and Mary, and infect me, is roughly 1-in-30,000. 

Now let’s just to a bit more math.  My daughter is going to be home for about two months.  At recent rates of infection, what’s my chance of getting infected, just being a normal member of the community, in my age bracket, for the next two months?  Again, not bothering to explain methods, because nobody ever cares.

By contrast, my risk of picking up a COVID-19 infection, in the community, in the next two months, at current rates, is roughly 1-in-93.  That’s simply based on the actual number of new infections in Virginia over the past two weeks, inflated up to two months.

Against that backdrop, the risk I face from my daughter (assuming a negative COVID-19 test) doesn’t even register.  For me to (e.g.) go grocery shopping, and then put my daughter in quarantine, is the worst sort of irrationality.  And since I plan to continue to go grocery shopping, there’s no way I’m going to do ANY of the items on the laundry list above.

William and Mary offers no advice.

Or, if they do, I sure can’t find it on their website.

I’m not worried, because the odds that my daughter is currently a COVID-19 carrier are very small.  New COVID-19 cases at William and Mary have become increasingly rare as the semester has progressed.  As of today, there are no known cases of active COVID-19 among William and Mary students.  And my daughter will take a COVID-19 test before returning home.  Between near-zero population incidence, and a recent PCR test, the odds that she’d be bringing COVID-19 into the household are zero, within rounding error.

As I’ve said several times on this blog, I think my daughter has more to fear from us than we have from her, in this regard.  Even more so now, as new cases in the community at large have ramped up.

But I was curious to see what William and Mary suggested, for students returning home.  Should they “self-quarantine” for a bit, or is that unnecessary?

Turns out, William and Mary offers no advice.  As near as I can tell, searching their website, their advice ends when the students move out of the dorms.  Whether or how to treat them during travel to home, or for the initial period at home, is never addressed.

After doing a few internet searches, this appears typical, and has been noted elsewhere.  Most colleges are treating this as if their liability ends at the border of the campus.  You’ve got strict instructions on how to move out safely.  And that’s it.

CDC advice:  Treat your student like a stranger.

The CDC, by contrast, tells you to treat your returning college student like a stranger.  For purposes of Thanksgiving:

People who do not currently live in your housing unit, such as college students who are returning home from school for the holidays, should be considered part of different households. In-person gatherings that bring together family members or friends from different households, including college students returning home, pose varying levels of risk.

The guidance then goes in, in a somewhat rambling style, to say:  Everybody wears a mask, no handshakes or hugs, social distance, stay outside where possible, and so on.

So the CDC offers advice based on a quick trip home for Thanksgiving: Treat your student like a member of some other household.  But they don’t really tell you what to do, given that this person is going to be living in the household for the next month or two.

They briefly discuss what to do with overnight guests, but the advice is both weird and unhelpful.  They seem fixated on preventing fomite infection (launder clothes and masks, store luggage in an isolated area) even though, elsewhere, the CDC acknowledges that the potential for fomite infection is virtually non-existent.

Anyway, the rest of the CDC advice boils down to the same:  Wear a mask, keep at least 6′ apart, interact outdoors if possible.

In particular, the CDC doesn’t even consider the possibility that your “guest” will have had a COVID-19 test just before arriving.  So, acknowledging the high false-negative rate of COVID-19 tests (Post #859), you will at least know the results of the test before they enter your household.  The CDC doesn’t consider that possibility, and so there is no advice, conditional on your guest having tested negative for COVID-19 just prior to arrival.

Anybody else offering formal advice?

Here, I am limited to what I can dredge up via Google.  So my method is to make one Google search and summarize results until I stop seeing anything new.

And I’m not really interested in social-media advice.  I’m really looking for somebody in a position of authority to have some defined statement, and, ideally, some empirical basis for making that statement.

Indiana department of health:  Quarantine at home with masks for two weeks after returning, regardless of test results.  Context:  “Indiana has had more than 12,000 COVID cases on college campuses, …”

Dr. Fauci and others, cited in  the New York Times.  ““It depends on where they’re coming from and what the level of infection is in the community they are in.”  “There is no right or wrong answer. It’s about the relative risk you’re willing to take,”  “It depends on the contacts in the home you’re going to. If you have an immunosuppressed person or a grandfather who’s 92 years old, the risk is great. If you’re going into a home with a healthy 45-year-old father and mother and a brother and sister in their teens, the chances of there being a problem are much less.”

Fauci also favors getting tested before returning home, despite limitations:  “You don’t want the perfect to be the enemy of the good — you can’t be 100 percent on anything,” Dr. Fauci said. “Between the testing place and going home you could get infected. But if you’re careful, you wear a mask and you test negative, you’ve diminished dramatically the likelihood there’s going to be a problem.”

Additional advice in that article, from other sources, is that students should not engage in risky behavior (e.g., going to bars) in the week before returning home.

Without attribution, the NY Times article says:  “If parents drive to pick up a student, or the student rides home with friends, all passengers in the car should wear a mask and ride with windows open if possible. If it’s too cold outside, open the car windows at regular intervals to let out contaminated air. Make sure the car heater or air-conditioner is using outside air rather than recirculated air.”

Which, frankly, strikes me as totally off-the-cuff and absolutely half-assed advice that anybody could have thought up.  I particularly like the part about opening the windows at regular intervals.

The rest of the advice seems to boil down to “quarantine/isolate as much as is feasible”, which also strikes me as half-baked and evidence-free.  Yes, that will reduce risk.  How much?  Is it worth it?  No clue here.

The AARP (formerly the American Association of Retired Persons):  Their expert wants your kid to get not one, but two tests, both negative, before returning home.  “Rebecca Lee Smith, an associate professor of epidemiology at the University of Illinois at Urbana-Champaign, says young adults should receive two negative tests four days apart, while self-quarantining or avoiding unnecessary exposure, before heading back to their families.”

This article has, almost word-for-word, the same advice about the car ride home that I criticized above in the New York Times article.  Also without citation as to the source of that advice.  So, presumably, there’s some root source for the advice about opening the windows occasionally, but I can’t figure out what it is.

Lexington, MA offers advice consistent with Massachusetts requirements for testing for persons arriving from certain states.  Their rule, which again has no notation as to source or evidence basis, is to quarantine seven days with a negative COVID-19 test, or 14 days without a test.  Sounds reasonable, but I have no idea if there’s any empirical basis for that.  And “discourage their college-age students from casual socialization with friends indoors and in groups.”

NPR’s article does’t seem to offer much in the way of unambiguous advice.  You’ve another advocate for getting tested twice, mask up, keep your distance, and so on.  Wind down your social activity at college a week before you return home.  Having the returning college student eat in a different room from everybody else — that’s new advice only found here.

Futurity’s expert starts by offering the same sort of nuanced advice as Dr. Fauci.  “Families should do their own risk analysis and not necessarily look at what other families are doing. A college student returning to a family with young, relatively healthy parents and siblings is a different situation … Look at what their college reported in regard to current infections and how many infections have been reported in the area where the college is located, especially if the student lives off-campus. Also, have a frank and honest discussion with your student about their recent activities and potential for exposure.”

Here’s advice from the Chicago Sun-Times, clearly in the context of a severe ongoing outbreak, as Chicago is under a 30-day stay-at-home advisory.  To cut to the chase, they recommend everything — isolating before coming home, getting multiple tests, isolating in the house, eating separately from everyone else, using a separate bathroom.  Stay clear of anyone who is high risk (elderly, pre-existing conditions).  Pretty much the superset of all advice offered anywhere else.