My Authors
Read all threads
1/ TESTING TESTING & MORE TESTING! 🇱🇧
Why the confirmed # of COVID-19 cases in Lebanon highly underestimates the actual # of cases?
@mophleb @WHOLebanon @thehealthnerds
#Lebanon #COVID19 #FlattenTheCurve #RaiseTheLine #healthNERDS
2/ Keep in mind, we can never know the actual # of cases because we cannot test the whole population. However, we should do as many tests as possible – especially during this stage of the outbreak – to gage the scale of the problem, isolate/ treat +ve cases & plan next steps.
3/ If we can’t test the whole population, how can we know the actual # of cases? We try to estimate; one way of doing so is by using the case fatality rate (CFR). CFR reflects the severity of the disease in a particular context, at a particular time, in a particular population.
4/ CFR (%) = (# of deaths/# of confirmed cases) * 100
Remember CFR is not constant and keeps changing over time; the only stable CFR estimate is calculated when the outbreak ends. In Lebanon, CFR on March 31 was reported to be 2.6% 👇
5/Calculating CFR from “current” total # of confirmed cases underestimates the risk of death because there’s a lag (15-20 days) from the time of diagnosis to death. So, patients who got diagnosed on March 31 may die within the next 15-20 days & won’t be counted in the current CFR
6/ To calculate CFR on Mar 31, we can go back 17 days (Mar 14) & use the total # of cases on that day (93).

A CFR of 12.9% seems very high compared to published rates ranging from 1% - 5%!
So what is it? Are the 93 cases on March 14 an under-estimate of the # of cases?
7/ Let’s ask the question in a slightly different way: Given that published CFRs range from 1-5% & total # of deaths on March 31 was 12, how many cases should have been on March 14 to lead to 12 deaths as of March 31?

Here are 3 scenarios:
8/ Now we have estimates of the possible # of cases on March 14. So, what is the potential # of cases on March 31?

Here are two scenarios projecting total # of cases based on doubling time of 5 & 7 days & % of cases captured out of the total potential estimate
9/ If we go with the scenario of 2.5% CFR & doubling time of 7 days, we would have 2880 cases by March 31. Based on the # of confirmed cases on March 31 (463), we are missing ~ 84% of potential cases (range 64% - 87%).
10/ Sensitivity analysis: Let’s estimate the total # of cases at CFR of 2.5% & doubling time of 7 days with the duration from diagnosis to death set of 10, 15 or 20 days:
11/ This exercise is not to estimate an exact # of cases; this is to demonstrate that we are missing a large # of potential positive cases who continue to spread the infection, and why we need to TEST MORE, a LOT MORE.
12/ Without increasing testing capacity, we won’t be able to evaluate whether the relatively small numbers we’ve been seeing the last few days are due to the effectiveness of containment measures or due to low rates of testing.
References:
Li et al. Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia. N Engl J Med 2020; 382:1199-1207.

Dorigatti I et al. Report 4: Severity of 2019-novel coronavirus (nCoV). Available from: imperial.ac.uk/media/imperial…
References:
Pueyo T. Coronavirus: why you must act now. Available from: medium.com/@tomaspueyo/co…

Jung S et al. Real time estimation of the risk of death from novel coronavirus (2019-nCoV) infection: Inference using exported cases. Available from: medrxiv.org/content/10.110…
@Rattibha please organize this thread. Thanks
Missing some Tweet in this thread? You can try to force a refresh.

Enjoying this thread?

Keep Current with Fatima Al Sayah

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!

Twitter may remove this content at anytime, convert it as a PDF, save and print for later use!

Try unrolling a thread yourself!

how to unroll video

1) Follow Thread Reader App on Twitter so you can easily mention us!

2) Go to a Twitter thread (series of Tweets by the same owner) and mention us with a keyword "unroll" @threadreaderapp unroll

You can practice here first or read more on our help page!

Follow Us on Twitter!

Did Thread Reader help you today?

Support us! We are indie developers!


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

Become a Premium Member ($3.00/month or $30.00/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!