As Omicron cases explode

We need a strategy for isolating folks who test positive

We need to think about the purpose of isolation clearly

Because if we don't get it right,

It'll both be hugely disruptive and won't keep us safe

So let's discuss what we need to do

First principles:

Why ask people to isolate at all?

Well, that’s obvious

We don’t want them spreading

So what we care about is CONTAGIOUSNESS

We want folks to isolate when they're contagious

So when are people contagious?

Well, it varies. A lot

OK, so what to do?

How long folks are contagious depends on two things

1. When they test positive (i.e. early in the phase of infection vs. late)

2. Their immune system's ability to clear the virus

Take the average person who tests PCR+ today

How long will they be contagious?

The average person who tests PCR+ today?

Some will be contagious for 2 days

Others for 5 or (rarely) 10 days

But here’s the kicker

Some for zero days – because they tested + after no longer being contagious!


But thankfully, we have tools to figure this out

So let’s look at what we know

Here’s a graphic from @FT by @jburnmurdoch that's adapted from @michaelmina_lab piece in @NEJM

Simply speaking, there are three periods of time you can be PCR+ (I label as A, B, and C)

Its an excellent graphic and critical to this whole story

5/n Image
There is very short pre-contagious period

Where folks are PCR + but rapid antigen negative

Labeled A

There is the contagious period: PCR + and Antigen +

Labeled B

There is post contagious period: PCR +, Antigen neg, which can last many, many days

Labeled C

Graph again Image
The graph shows “infectious” period of about 5 days

But it can be longer

That’s why CDC defaults to 10 days to be safe

But here's the thing

10 day isolation uses the mental model that either

People test + in Phase A/early Phase B

Or have symptoms beginning of phase B

But many people have little or no symptoms (especially vaccinated folks)

And many folks get tested late in phase B or even in phase C

Which is why studies show that many PCR+ have high CT values (low viral load)

These are people testing positive but no longer contagious!

So what to do?

We need a simple, workable solution that

Works across scenarios

Works for everyone, not just in healthcare

So here's why 5 days of isolation and negative antigen test is reasonable, even cautious

Antigen tests ("lateral flow") are contagiousness tests (graph) Image
So for average person

If you isolate for 5 days, you are likely no longer contagious

But for rare person who might still be?

That’s where antigen “contagiousness” test comes in

Negative antigen on top of 5 day isolation?

Pretty good evidence you are no longer contagious
But, what about false negative antigen test (i.e. person still contagious)?

That's pretty rare

But if you want to be extra careful (for nursing home workers), you could require 2 negative antigen tests

At that point, I’m not sure why you’d continue isolating someone

Two more things

1. If you test + on rapid antigen, you are contagious (vaccinated or not)

And isolating for 5 days and repeating antigen test makes sense

2. Data from Delta suggests vaccinated folks have shorter contagiousness period

Expect same with Omicron

Therefore, if you want to be even more cautious

Limit 5 days isolation and a neg antigen test to only vaccinated folks

NYC strategy: 5 days isolation and then high quality masking for another 5 days

That’s reasonable

I’d love a negative antigen test on top if possible

Bottom line?

Isolating COVID + people all about stopping transmission

Different people contagious for different periods of time

10 days isolation for everyone is unnecessary

Luckily, we don’t have to guess

We have antigen tests (I know, not enough…but they're coming)

5 days and 1-2 neg antigen tests should be enough to end isolation

Not just for healthcare workers

But for moms and dads getting back to kids

Hourly workers who don’t get paid when home

Really for anyone who doesn’t want to be isolating when they don’t need to be


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More from @ashishkjha

Mar 17
So, as they say…

Some news

For all the progress we’ve made in this pandemic (and there is a lot)

We still have important work to do to protect Americans’ lives and well being

So when @POTUS asked me to serve, I was honored to have the opportunity…
This President has spoken the truth about this virus

Has prioritized policies based on science and evidence

Americans are going back to work and school

And it is an honor to work under his leadership

One focused on the health and well-being of the American people
We are in so much of a better place with vaccines, diagnostics, increasingly, therapeutics, and much more

Much of this because of the superb leadership of Jeff Zients

Who has used the levers of the US government to make available these miracles of science to the American people
Read 9 tweets
Mar 3
With infections down more than 90% since highs just 6 weeks ago

It is tempting to decide the pandemic is over

It is not

During this upcoming lull of infections (and falling deaths),

It's time to prepare for whatever is next

So what to prepare for -- and how?

The two questions I get asked most often these days are:

1. Will we see future variant

Answer: I don't know. No one does. Reasonable to assume we will. Let's hope we don't

2. Will we see future surges

Answer: most likely yes. Hope not

But remember: hope isn't a strategy

So with possible future variants and surges

We should focus on the playbook:

1. Surveillance
2. Vaccinations
3. Testing
4. Ventilation/filtration
5. Masking
6. Therapeutics

Much of this is in today's White House plan

(disclosure: I, others have shared our ideas with them)
Read 10 tweets
Feb 26
For two months, I've said we're entering a new phase of the pandemic

A phase marked by a lot of population immunity, a more immune-evasive but less virulent virus

This new phase requires new metrics

My @nytopinion piece on the latest CDC metrics…
Fundamentally, new CDC metrics get it right


Because cases no longer are the most important measure

For nearly 2 years, for every 1000 cases, you could reliably predict 50-80 would end up in the hospital and about 15 to 20 people would die

That was true in 2020. And 2021
That tight link between cases --> hospitalizations --> deaths was true for original strain

And for Alpha
And for Delta

But Omicron severed that link (mostly)

Now, if you told me there were a 1000 new cases

I can no longer tell how many will end up hospitalized or dead

Read 9 tweets
Feb 18
Nationally as infections return to pre-Omicron surge levels,

Two states I've tracked closely are California & Florida

They're both large with diverse populations, similar seasonality, different COVID approaches

So what can we learn from comparing them?

A few things

First, let's compare how they did on infections during Omicron surge

Strikingly similar (see graph)

Florida peaked earlier, California a bit later

Cumulatively, they had nearly identical infection rates

About 9.50% of Floridians got infected while 9.54% of Californians did
So at first blush, looks like their different COVID strategies did not end up mattering much

But, when we look at deaths,

A different, surprising pattern emerges

Cumulatively, Florida had 33% more deaths per capita than California during Omi surge

That's a lot


Read 6 tweets
Feb 16
As the Omicron surge of infections abates,

Its worth reflecting on few lessons we learned

Today, lets' discuss whether Omicron was indeed "milder"

Short answer? Yes it was

But it still caused a devastating loss of life

And that's a lesson for managing future waves

First, let's talk about how we might assess whether Omicron was "milder" than Delta

One way is to look at case fatality rate

Remember CFR is proportion of identified cases that end up dying

Throughout the pandemic, the CFR of of COVID in the US has been between 1.5% to 2.0%
CFR is usually 1.5% but rises to 2.0% during surges as hospitals fill

Meaning that as hospitals fill up, admission thresholds rises...and ability to care for sick people diminishes

Its bad to be sick during a COVID surge

So what happened to CFR over the past 2 months?
Read 10 tweets
Feb 10
Let's discuss a path forward for masks in schools

I've been a strong proponent of masking in schools

So as we enter a new phase

Do we need to keep masking for the foreseeable future

I don't think so

Should we ban masks in schools today?


Let's find a middle path

First, let's talk evidence

Do masks work to reduce transmission?


What about in kids?

The evidence is less strong but clearly, the weight of evidence says that masking also works in kids

Are there harms?

Not much evidence either way but there could be

So given the (imperfect) evidence

Masking in schools was important while two things were true:

There were no vaccines for kids

Large surge of infections in the community

Now, as we enter a new phase

Every school-age kid can be vaccinated

And infections are getting low

Read 10 tweets

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