Share this page!

A Marm Kilpatrick Profile picture
Twitter logo
11 Sep, 10 tweets, 4 min read
Interesting thread on possible reasons for resurgence of cases in NY & Madrid.
Some useful observations but several key flaws.
Quick thread.
-Comparison would have been better for NYC & Madrid. Not sure why data from a whole state is being compared to a city. Maybe b/c @_MiguelHernan wants to claim seroprev is similar b/w 2 locations which is NOT true about NYC (25%) & Madrid (15%) but is for NYS & Madrid?
-@_MiguelHernan claims diff #s of contact tracers made a difference but our recent paper () shows this is unlikely to be true. If they had 200 tracers in early July this would be plenty to trace the <100 cases they had in July (cnecovid.isciii.es/covid19/#ccaa).
@_MiguelHernan also suggests that opening restaurants played key role. It's quite possible that open restaurants led people to have close contact/dinner w/ people from other households, but evidence for b/w table transmission is anecdotal & likely makes up tiny frac/<1% of cases.
If anyone has seen study with % of cases in a city/county/state that are traced back to b/w table transmission at restaurants please link here. Similarly, if anyone has seen data for % of cases that arise from work activities (not social), please link here. Outbreaks #s aren't %s
There is far too much hand-waving and policy being made about the importance of indoor dining or work-related transmission w/ no actual quantitative evidence on its relative importance. I am not aware of ANY study or quantitative data on this critical topic.
My own speculation on key diffs b/w NYC & Madrid are:
- Differences in behavior (possibly driven by open indoor dining @ restaurants, but not directly resulting from b/w table transmission)
(cont)
- Different levels of immunity (~2x in NYC vs Madrid) both below herd immunity threshold:
- Now that cases have risen to much higher levels, insufficient contact tracing capacity ().
(Note that due to diffs in testing, case counts in Feb & Aug not really comparable),
Finally, while re-opening businesses has repeatedly led to increases in cases, as it did in Spain, it doesn't have to be this way. Lockdowns are not the only way:

• • •

Missing some Tweet in this thread? You can try to force a refresh
　

Keep Current with A Marm Kilpatrick

A Marm Kilpatrick Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @DiseaseEcology

A Marm Kilpatrick Profile picture
11 Sep
How increasing #COVID19 cases overwhelm contact tracing (CT) & lead to runaway/accelerating epidemics. Also, how delays make CT ~useless.
(bonus: how heterogeneity can lead to highly variable timing of epidemics)
New paper from @billy_gardner_ & me.
medrxiv.org/content/10.110…
Thread
Background:
Rapid spread of COVID19 (cases/case Rt = ~2-3 every 4-6d) initially led to huge epidemics in many places (e.g. NYC, Italy, Spain, etc.) which led to shutdowns to limit transmission. However, some countries were able to limit transmission w/out shutdowns.
The example many point to is Singapore which implemented a very strong public health response, including aggressive contact tracing (CT). Other countries (S Korea, Hong Kong, etc.) also have used CT effectively.
statnews.com/2020/03/23/sin…
Read 31 tweets
A Marm Kilpatrick Profile picture
24 Aug
New paper on children's viral loads (from symptomatic AND asymptomatic kids) & fraction asymptomatic, split out by 3 age groups (0-5, 6-13, 14-20).
Q thread

medrxiv.org/content/10.110…
Background
Still substantial uncertainty about how infectious children are, & still no estimates of age-specific fraction of infections that are asymptomatic.
Previous studies on viral load in kids came from symptomatic children (often very sick children) who might be anomalous.
Measuring fraction w/ asymptomatic infections is key b/c it helps us interpret other data that are based on detecting symptomatic infection. Long discussion here:

Read 14 tweets
A Marm Kilpatrick Profile picture
23 Aug
Helpful thread by @maiamajumder on merging bubbles. However 2 measures she lists for protection (hand washing, masks) aren't most important issue. The #1 issue is: do people in each bubble have sustained (minutes) close (<2m) contact w/ other people, especially indoors.
S thread
Transmission of COVID19 via infected surfaces is so rare, one can list all the cases where it was likely mode of transmission (). Focus on handwashing is red herring & should stop. Far more important is spending time near other people, especially indoors.
Masks help, but again, spending long periods of time indoors w/ people outside your bubble, even with masks is risky (). #1 question I'd ask before merging bubble: When you meet people you don't live with, do you do it outside, with 2m+ distance?
Read 4 tweets
A Marm Kilpatrick Profile picture
20 Aug
Trying to screen for #COVID19 infection?
Another failure.
New paper w/ 1st evidence for protection by neut. antibodies to SARS-COV-2/#COVID19. Nice thread below w/ details.
Not receiving as much discussion in same paper is failure of screening at start of trip.
S Thread
122 crew members leaving on fishing boat were screened for RNA and antibodies (Ab) 1-2d before departure. All tested negative for RNA but 6+ for Ab, w/ 3+ for neut Ab.
16d later 1 person got sick & boat returned. 103/117 tested positive on/after return for RNA or seroconverted.
Paper & thread above focuses on N=2 of 3 people w/ neut Ab being PCR neg& 1 being weakly PCR pos (argued to be residual shedding, not infection) suggesting protection. Paper also mentions issues w/ Abbott test suggesting N=6 had Ab but their analysis indicates only 3 w/ neut Ab.
Read 13 tweets
A Marm Kilpatrick Profile picture
14 Aug
Do we finally have evidence for COVID immunity?
Fast spreading @ABC new story claims 2 things:
1) We now know immunity is protective.
2) It lasts *UP TO* 3 months.
*NEITHER* are based on data & CDC's guidance doesn't actually say people can safely interact with others.
Thread
Story is based on this text on CDC website about quarantine for "People who have been in close contact with someone who has COVID-19". It is NOT on a website entitled: Had COVID-19? Want to have some fun?
It says:
"People who have tested positive for COVID-19 do not need to quarantine or get tested again for up to 3 months as long as they do not develop symptoms again."
So where did ABC story come from and where did CDC guidance come from?
Read 10 tweets
A Marm Kilpatrick Profile picture
8 Aug
Is herd immunity now high enough to contribute to reduced transmission of #COVID19?

Thread from @trvrb is provoking substantial discussion as it should. I'd like to add a few details that aren't included.
Background
For diseases that induce immunity, transmission wanes as fraction of population gets infected & recovered because infected people mostly contact immune people. At a certain level (the herd immunity threshold, HIT) cases shift from growing (Rt>1) to shrinking (Rt<1).
HIT has been huge topic of recent discussion, in large part b/c of uncertainty of what HIT is for #COVID19:

tl;dr HIT based on simple models (if R0=2.5, HIT=1-1/R0=60%) are too high but by how much isn't clear.
Read 24 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!

Like this author's thread?

Get email notifications when new thread is out from this Author!

Check out other threads from this Author!

Read all threads by @DiseaseEcology