[Update: Illinois Passes Quarantine Threshold] With Illinois COVID-19 Cases Climbing, Will Chicago Require A Quarantine For Anyone Who Has Recently Been In Illinois?

Chicago. mindfrieze [CC BY-SA 2.0], via Wikimedia Commons
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Update, 9/2: Both Illinois and Indiana have climbed over the threshold to be subject to the Chicago quarantine. Unsurprisingly, people from Illinois and right across the border in Indiana have been given a special exemption and won’t have to quarantine if they want to visit Chicago. Maybe it’s time to ditch the quarantine, raise the threshold, or use another metric?

Originally posted on 7/27:

Earlier this month Chicago Mayor Lori Lightfoot took a page out of New York Governor Andrew Cuomo’s playbook and added a 14 day quarantine for people coming from states with a high infection COVID-19 rate.


While NY requires just 10 COVID positive cases per 100,000 residents over a 7-day rolling average to be added to the quarantine list, Chicago requires 15 cases per 100,000 residents. NY will also add states with a 10% or higher positivity rate over a 7-day rolling average to their list, while Chicago ignores that metric.

NY currently requires a 14 day quarantine if you come from 31 states, though that is very likely to climb when the this week’s list is announced.

Based on the current COVID spike in Illinois, it’s looking probable that the state will be added to NY’s quarantine list in the near future. Yesterday’s COVID positive numbers in Illinois were 1,541, which divided by a population of 12.67MM means 12.2 positive cases per 100K residents. We’ll have to wait and see what the numbers are based on the 7 day rolling average.


Positive cases always seemed like a strange metric to use.

Ohio recently introduced a quarantine, but it’s based on states that have a testing positivity rate that exceeds 15% and not based on total cases. That seems far more sensible to me.

Why should a state be penalized for doing a lot of testing and finding more cases? What really matters is what percentage of those tests come back positive, and that’s something that won’t arbitrarily change based on how many actual tests are performed.

NY has fewer cases than CA or FL, but that’s because they didn’t do the kind of testing when they got slammed in March that is being done now.

To illustrate using very rough numbers and estimates, NY has 416K cases and 32.3K deaths. Based on the CDC’s current best estimate of an Infection Fatality Rate of 0.65%, that would mean the actual number of cases in NY was 4.96MM out of a population of 19.45MM. In NYC there were 228K cases and 23K deaths. Using that same math would impute about 3.54MM actual cases out of a population of 8.39MM. That would lend some credence to herd immunity in NY being the primary reason for the dropoff in cases there, and not the state’s action.

On the other hand, FL has 424K cases and 5.8K deaths. Using that same math would impute about 892K actual cases. Granted that FL positive case numbers are much higher currently and deaths are a trailing indicator, which will mean more total actual cases as deaths climb, but total cases is a very blunt number to use for comparison purposes.

Of course these back-of-the-envelope calculations are just rough extrapolations and not scientific data. For example, Cuomo’s numerous failures in NY likely contributed to a higher than average infection mortality rate there, which will change the math on total cases. And the CDC’s Infection Fatality Ratio best estimate is currently 0.65%, but can be anywhere from 0.5%-0.8%. But the numbers show that total cases are a poor indicator of success against COVID-19 or as a basis for quarantine.


Update: Based on a question in the comments below, I’ll try to illustrate the difference between Chicago’s quarantine list and Ohio’s quarantine list:

  • Scenario 1:
    • If my fictitious state of 20MM people only administered 100 tests and 90 come back positive, that’s only 90 total cases which is much less than 15 cases per 100K residents, so we would not be on Chicago’s quarantine list.
    • However that would be a positivity rate of 90%, so we would be on Ohio’s more sensible quarantine list when positivity rate exceeds 15% of tests.
  • Scenario 2:
    • If my fictitious state of 20MM people administered 1MM tests and 3,100 come back positive, that’s more than 15 cases per 100K residents, so we would be on Chicago’s quarantine list. We would effectively be punished for administering so many tests.
    • However that would be a positivity rate of just 0.3%, so we would not be on Ohio’s more sensible quarantine list.

OH quarantine map, based on test positivity rate:

Positivity Rate Over and Under by State



Mayor Lightfoot announced today that nearby Wisconsin will soon be added to the Chicago quarantine list this week after exceeding the threshold of 15 positive cases per 100K residents. 

Of course the real irony will be if Illinois exceeds the threshold of 15 positive cases per 100K residents. Based on the current trajectory, that seems like to happen over the coming weeks.

That would put the city of Chicago in the rather uncomfortable position of having to walk back the quarantine, increase the threshold, change the metric used, or look rather hypocritical if they leave things as is. After all, why should people coming from a state that exceeds 15 cases per 100K be required to quarantine if Illinois meets that threshold?

What do you think Mayor Lightfoot will do if Illinois exceeds her quarantine threshold?

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79 Comments On "[Update: Illinois Passes Quarantine Threshold] With Illinois COVID-19 Cases Climbing, Will Chicago Require A Quarantine For Anyone Who Has Recently Been In Illinois?"

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She’ll probably just call someone a name

Sam Finkelstein

It’s all politics from Day 1 and doesn’t usually change anything on the ground. So I doubt anything will be changed other than making an exception for the rest of Illinois.


You have a typo in the title. Should say “will NY require quarantine…”


Headline needs correcting

Ilene Van Houter

Isn’t everyone in Chicago in Illinois?


Im lost. “Why should a state be penalized for doing a lot of testing and finding more cases? What really matters is what percentage of those tests come back positive”

isnt the definition of finding more cases =tests that come back positive?


Not according to the media. If you’ve noticed they almost exclusively tout the raw numbers for shock effect, or worse, list or graph the cumulative infections as if every case is still active.


Love the title.

Sparky Leach

Congrats Dan!
You were one of the firsts for posting about masks being beneficial.
One of the firsts about posting about certain people being super spreaders.
Now be one of the first about current viral load of those people who are infectious being of concern not a positive result.
Medcram link https://youtu.be/h7Sv_pS8MgQ with snippets from this week in virology.


Also one of the first to post about quantas not selling international tickets until at least july 2021, which coincidentally or not, is when Google announced today they would be extending work from home provisions for all their employees.


Nice! The This Week in Virology(TWiV) guys and gals were thinking or renaming their podcast to every other day in virology since they have been putting out podcasts a lot more often. Thanks for the response Dan! Thanks for being ahead of the curve in multiple ways. Good link on the T-cell assays. Here’s a gofundme for a T-cell assay machine for one of the researches’ lab on TWiV that she did not directly ask for, but I thought I would give a shot. Maybe best donating to Drew University and asking for funds to be directed to the lab https://twitter.com/BioProfBarker for the tax write off.


Im heading to Denver with a stopover in Chicago. Would that be a issue?


“Herd immunity”. You just touched the third rail of covid discussions. Duck!

Seriously though, you hit the nail on the head. States are using arbitrary measures. New Hampshire is ok with travelers from all New England States but not NY or NJ which have great metrics.

Vermont has a cutoff of 400 active cases per million and its anyone’s guess as to how active cases are calculated and there doesn’t seem to be any weight given to testing numbers or positivity rate.


And the list goes on. So many states have illogical and contradictory criteria or arbitrarily ok neighboring states that have far worse metrics than more distant states from which they require travelers to quarantine. How illogical is that?

Raw positives are simply not an objective standard on their own.There ought to be one objective set of standards, taking into account rolling seven day average positivity rate, hospitalizations, fatalities, or a combination of the above. Then every state could make a determination of the number they are comfortable with.


Pointless discussion as absolutely nothing is being done re: quarantine, regardless if driving or flying into the city. Once that changes then we can talk.

Texas Totty

It may not be enforced by the government but it’s enforced on another level. People from those states aren’t being let into stores, doctor’s offices, and shuls. Even with negative tests and positive anybody tests.


You’re assuming ppl are telling the truth. In reality, most are not.


Why do things that seem so sensible to laymen, so hard for politicians to comprehend? Haven’t been more disappointed in our leaders (coumo Trump etc) in a long time….


“though that is very likely to climb when the this week’s list is announced”
When is that?


Open the country!! The elderly and immunocompromised may want to remain cautious, but enough is enough! So much more damage is being caused by these shutdowns!

Leave Chicago while you still can

Mayor Lightfoot is more concerned with tearing down statues of Christopher Columbus, than her black residents being slaughtered like worthless dogs on the streets of Chicago. What a failed disgrace. She’s 100 times worse than Rahm Emanuel was.


Dan, I gotta say I love the title (especially because you completely confused everyone!) and the article.


LOL!!!!! Quarantine is meaningless in America


“What really matters is what percentage of those tests come back positive, and that’s something that won’t arbitrarily change based on how many actual tests are performed.”

Not true at all. That would only be the case if the people you would test are pulled from a random sample. If it’s not a random sample (and it isn’t here), then you can’t just prorate numbers across sample sizes.

It’s also stupid because in this case, state lines are just arbitrary borders…. there are cities in states that are on the quarantine list which have lower numbers than cities not on the quarantine list…. but if you come from the former you’d have to quarantine, whereas if you came from the latter you wouldn’t. It’s not like someone can be on the Oregon side of the Oregon/Nevada border, and if you drive 2 miles over the border your chances of catching it suddenly triple.

There is no single good metric out there to base these decisions on, which is why it’s stupid for elected officials to base it off of one metric. And that’s before you even get to the impossibility of enforcing it…..


This is very true


I lol’d at the title


Quarantine rules apply when traveling to or from place to place. Since Chicago is more or less always in and a part of Illinois, Quarantine rules would not , as in never, come into effect. It would be like doing self distancing.

Althought the wisconsin application does have more interest since many people from illinois own property and vacation in wisconsin and travel back and forth when going “to the lake”.
So the quarantine in this instance would be both bad for tourism in wisconsin, and at the same time, limit the movement of illinois residents to their lake homes and cabins in wisconsin.

In either case, whatever the metric, small sample size is small sample size and layering quarantines is in effect, leading up to a de facto lockdown .


Quoting from an article:
“Mayor Lori Lightfoot said that no one has been fined for violating the quarantine order since it was implemented earlier this summer…..This has really got to be about not just fining people into compliance, but about educating people to understand the risk factors that are out there.”


Lightfoot is proving to be a real disaster.Besides for doing a terrible job running the city she is crude and obnoxious.She wont be criticized by to many in the current atmosphere.She is after all, the right race, the right gender and the right persuasion.She may well be the nail in Chicagos coffin


Rahm Emanuel was mayor of Chicago from 2011 to 2019? And yet already in 2020 Lightfoot is to blame for the Chicago problems that the Rahm Emanuel too couldn’t fix and let Lightfoot inherit?

What’s the position of RahmE and his doctor brother on Chicago trying to depress traffic to Chicago as part of the coronavirus response? Reducing traffic and population mixing is not necessarily a senseless measure to try to put a brake on this coronavirus spreading.


Your original point about total cases has some validity but your comment about Ohio makes equally little sense. What relevance is positive percentage of tested? Clearly, the people going to get tested are sick with something and exhibit symptoms thus, you are favoring a system that has confirmation bias. The State of Ohio is not testing every household regardless of symptoms so percentage of those tested that test positive is also quite a meaningless metric.


Of course it makes sense. You can’t extrapolate to the general population but that’s not the point. The point is to compare one state to the other as well as to look at the trends in that state. Percent positive figures will not be as influenced by the number of tests that are administered so you can compare states that are doing massive testing with those doing less and still have a meaningful comparison.

Warren hsfder

Put more police on her street to protect her sorry ***

Dave Weiman

Problem with the data for quarantine ridiculously flawed Son many different ways to get the wanted answer These figures do LIE!!


There is another factor to consider. In NY especially in the frum community the doctors are telling people that are symptomatic not to do PCR testing because they are reported to the city and state. And there is concern that if the numbers rise they will shut down the schools and shuls. Instead they are doing the rapid tests which are not being reported. So the only people whose tests are being reported are those that don’t have symptoms. The end result is that you are getting an artificially low number on positive tests.


Maybe it is time people started to again take his seriously and reduce the spread of the disease though social distancing. Too many of my neighbors have company over for meals and stopped the general wearing of masks.
Deaths from Covid continue, recently the Rosh HaYeshiva of Telshe Yeshiva Chicago. It is time for continued action, not jokes.


@Dan, you are missing a critical point. NY had so many deaths as a result of an overwhelmed and tax health system. They also didn’t have the knowledge and expertise on the virus that they currently have.

Lastly, it slammed the nursing home centers bringing the numbers of deaths up dramatically.

Thus, the actual fatality rate could have well been 2 percent. In that scenario you have about 1.5 million cases in NY.

With these above numbers NY is far from herd immunity (although certain segments of the population will be closer to it then others).


Early on, for purposes of putting on lockdown restrictions and then later rolling them off, Illinois was segmented into 11 subregions. Chicago being one of them.

So referring to chicago restrictions as seperate from the rest of illinois in the instances of control measures like quarantine, while also being combined with the “downstate” portions of illinois for purposes of aggregate statewide measures or state to state comparisons, is generally understood.

This may not be widely understood in less urbane locales such as cleveland and ohio. Addressing Chicago rates of infection, and appropriate responses, specifically rather than lumping together with “downstate” is not unheard of in either of those parts of illinois.


“Ditch the quarantine” aka let people die needlessly? How can you even suggest such a callous thing? The numbers of deaths are only relatively low BECAUSE of the quarantine.