@thattai I am glad to see decent language now unlike your earlier posts. I hope you can make this a habit. Your argument, as I understand it, is not that the model went wrong in March, rather that policy makers were misled by it. If yes, your argument is based on flawed premise.
Policy makers do not make decisions based on one input. They collect them from multiple sources. While we did give our feedback to them last month, and it was received graciously, they were skeptical about our predictions. Seemingly they had better inputs. 😊
As for our model, it adopts a very different approach to parameter estimation. An approach that is becoming ubiquitous: use data. If one argues that it needs to be improved, I will readily agree. However, to retire? That is truly bizarre!
Our model needs time for a phase to stabilize (as explained at multiple places) but once it does, the predictions have been fairly accurate. For example, on 24th April, we predicted a range for peak value and period of new infections for India. And it continues to hold.
Other models that I have come across make very different predictions. But maybe I am not fully aware. Since you appear to be, please share if the models that you are aware of, make similar predictions or not.
Then it is a simple matter of waiting out for a few days and see which one comes closer to reality.😊What do you say? If we do not get it right, we will get back to work to improve the model further. And if we do, I hope you will get back to your research with renewed vigor!

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More from @agrawalmanindra

23 Apr
I have been asked by many people about details of the SUTRA model. We have a preprint uploaded at arxiv.org/abs/2101.09158. It describes how we compute parameter values and phase changes.
India projections can be found in this thread:
Read 4 tweets
18 Apr
@stellensatz @Ashutos61 @Sandeep_1966 @shekhar_mande Starting a new thread for India. I updated India curve last on 14th with suggested peak at ~190K. Past few days have breached this value massively. This led to a discussion amongst us (me, Prof Sagar, and Gen Kanitkar).
The problem is that parameters of our model for current phase are continuously drifting, and so it is hard to get their value right. We decided to switch to predicting "active" instead of "new" infections. Former is about 10x of latter and hence less prone to fluctuations.
Indeed, it turned out that the trajectories are better matched. See plot below for the entire timeline. Image
Read 26 tweets
8 Apr
@stellensatz @Sandeep_1966 @Ashutos61 @shekhar_mande Starting a separate thread on district level predictions. The predicted trajectories do not match as well as for states because of smaller population.
Let us start with Pune -- it was earlier posted on thread on states. It remains on track to peak during April 12-15 at around 11.5K infections/day. Image
Next Mumbai where infections are increasing quite fast. The rise will continue for another couple of weeks and likely to peak during Apr 21-25 at around 13K infections/day. Image
Read 159 tweets
25 Mar
@stellensatz @Ashutos61 @Sandeep_1966 @shekhar_mande This pandemic has a way of embarrassing those making predictions😀. We are indeed in the midst of second wave now. Of course, this wave is being driven primarily by Maharashtra. 1/n
We had to wait for a couple of weeks for the new trajectory to stabilize. Here is what we found: the spike observed in many states is primarily due to a significant increase in contact rate (parameter beta). This parameter determines how fast the pandemic is spreading. 2/n
Consider India. Contact rate has doubled in March (0.24 to 0.48). This results in plot below. The peak is expected to arrive in mid-April at between 70-80K new infections per day. 3/n Image
Read 143 tweets
8 Mar
@stellensatz @shekhar_mande @Ashutos61 @Sandeep_1966 Covid infections are picking up in India again. Interestingly, only a few states are contributing to this spike. Why is this happening? Our model SUTRA provides some clues. 1/n
First, let us look at Maharashtra. In the picture, blue curve is recorded daily new infections (averaged over a window of seven days) and orange curve is prediction of the model. According to the model, the latest spike is due to significant increase in contact rate. 2/n Image
Contact rate represents average number of people infected by an infected person in one day. For Maharashtra, it went from 0.3 to 0.5. The peak should arrive within two weeks. 3/n
Read 9 tweets
16 Dec 20
This article appeared today in Print: theprint.in/health/india-i…. The reporter had called me in the afternoon and asked some questions about our model. I explained to her the conclusions including the fact that a large number of infected people in India showed few symptoms. 1/n
To highlight this point, I mentioned that, according to our model, only one in 90 cases have been reported. And the unreported ones are primarily due to being asymptomatic. However, this ratio is not uniform across regions. 2/n
In Delhi it is around 1:25 while in UP/Bihar it climbs up to around 1:300. Unfortunately, the report has spun this in a different direction. The unreported cases become "missing ones". The implication being that our system has somehow goofed up by not detecting them. 3 /n
Read 9 tweets

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