Vanity - Ebola model projects future case based on Daily Transmission Rate

Self | September 15, 2014 | Scouter

[scouter]

My User Name on Free Republic is Scouter. I have been a member of Free Republic for 14 years. I don't write many vanity posts, but I consider this one to be very important. I had been working on this post for several days, and I was planning to post it tomorrow. But the Drudge Report headline CDC: PREPARE FOR EBOLA has moved up my timeline.

I have developed a model for making future projections of the number of Ebola cases. I have undertaken this project for several reasons. First, out of simple professional curiosity. Second, I believe the time has come to be concerned and to prepare for the possibility that the Ebola epidemic could spread to other countries, including the United States. And third, my daughter will soon begin working as a nurse in a major Pediatric Intensive Care Unit, which will likely see some of the first Ebola cases in the United States, should it make an appearance here.

I am not an epidemiologist, and I have no inside knowledge about the current Ebola epidemic. But I have spent the last 26 years of my career applying computers to the practice of medicine and to medical data. I hold a Master's Degree in Medical Informatics from a major university known for their expertise in that field. I currently work in that field at a large, famous, metropolitan teaching hospital. I am remaining anonymous only because I don't want my employer to be held responsible for this post in any way. It is my work exclusively, and I am responsible for any information or projections it makes.

The numbers produced by this model are "projections", not "predictions". That is to say, I do not predict that there will be x number of Ebola cases on any given future date. Rather, I "project" into the future, assuming a constant Daily Transmission Rate (DTR), based on past data. Any number of factors can influence future DTR, in either a positive (bad) direction, or in a negative (good) direction. There is no way to know how these factors will actually play out. If there were, then we would be able to make actual preditions. As it is, we are left only with the ability to say "If Ebola continues to spread at the same rate it has been spreading for the past x number of days (or months), then this is approximately how many people who will have contracted the disease as of this particular date in the future." Not ideal, for sure, but still quite useful to understand the seriousness of the situation.

I have validated the model based on actual data by calculating the DTR for various periods of time and comparing the model's projections with what actually happened in subsequent periods. This is the same concept that is being used by epidemiologists at CDC and elsewhere. It is a valid method, within the constraints I have mentioned above. My model has been completely in line with projections I have seen quoted in the mainstream news. It works quite well. If anything, my model's projections are a bit more conservative than some projections you may have seen in the mainstream media. I just take them out further than you have seen in other places.

That being said, the following projections are based on the Daily Transmission Rate (DTR) from June 1 through September 10, the last date for which I have data. The DTR has remained relatively stable over that period. To be conservative I assumed that the reported number of cases represent the true size of the epidemic. However, the WHO, CDC, Medicins Sans Frontieres, and Samaritan's Purse all agree that the number of reported cases represents only 25% to 50% of the true number of cases. I have decided to be conservative in the numbers published below, but the model allows you to adjust this percentage.

As you review these projections, remember to pray for all those who are currently affected by this terrible disease, those who have it, those who will die, and their families. Do not forget that these are real people with eternal souls, who will either go to heaven or to hell, depending on whether or not they die in friendship with God. Pray, too, for an end to this epidemic. Do not underestimate the power of prayer!

The following projections assume that the currently reported cases represent 100% of the true epidemic size. In other words, that there are no cases that were missed by the epidemiologists. We know this not to be true, so we know that the "best case" is something worse than this, assuming the Daily Transmission Rate remains stable.

Scouter Ebola Projection Model Version 1.0 - Ebola Case Projections

*********************************************************
Projection Parameters
*********************************************************
Start Date: 6/1/2014
End Date: 9/10/2014
Reported cases represent 100% of the true epidemic size
Daily Transmission Rate (DTR): 1.00422415489918
*********************************************************

Weekly for the Next 8 Weeks

Date        Cases                 Deaths                Daily New Cases       Daily New Deaths      
==========  ====================  ====================  ====================  ====================
09/10/2014                 4,845                 2,376                   171                    84
09/17/2014                 6,227                 3,054                   219                   108
09/24/2014                 8,003                 3,925                   282                   138
10/01/2014                10,285                 5,044                   362                   178
10/08/2014                13,218                 6,482                   465                   228
10/15/2014                16,988                 8,331                   598                   293
10/22/2014                21,833                10,707                   769                   377
10/29/2014                28,060                13,761                   988                   485


End of Month for the Next Year from the End Date

Date        Cases                 Deaths                Daily New Cases       Daily New Deaths      
==========  ====================  ====================  ====================  ====================
09/30/2014                 9,923                 4,866                   349                   171
10/31/2014                30,146                14,783                 1,061                   521
11/30/2014                88,357                43,331                 3,111                 1,526
12/31/2014               268,427               131,637                 9,451                 4,635
01/31/2015               815,475               399,911                28,713                14,081
02/28/2015             2,224,815             1,091,055                78,336                38,416
03/31/2015             6,758,941             3,314,601               237,983               116,707
04/30/2015            19,810,535             9,715,135               697,531               342,071
05/31/2015            60,183,993            29,514,379             2,119,084             1,039,204
06/30/2015           176,399,989            86,506,991             6,211,061             3,045,920
07/31/2015           535,899,508           262,806,446            18,869,075             9,253,441
08/31/2015         1,628,051,594           798,400,534            57,323,860            28,111,763
09/10/2015         2,329,918,242         1,142,597,677            82,036,655            40,230,979

The following projections assume that the currently reported cases represent 75% of the true epidemic size. Remember that Medicins Sans Frontieres, Samaritan's Purse, the CDC, and WHO all agree that the number of reported cases already vastly underestimates the true size of the epidemic. They say by a factor of 2 to 4.

Scouter Ebola Projection Model Version 1.0 - Ebola Case Projections

*********************************************************
Projection Parameters
*********************************************************
Start Date: 6/1/2014
End Date: 9/10/2014
Reported cases represent 75% of the true epidemic size
Daily Transmission Rate (DTR): 1.00422415489918
*********************************************************

Weekly for the Next 8 Weeks

Date        Cases                 Deaths                Daily New Cases       Daily New Deaths      
==========  ====================  ====================  ====================  ====================
09/10/2014                 6,460                 2,376                   235                   115
09/17/2014                 8,373                 4,106                   305                   149
09/24/2014                10,853                 5,322                   395                   194
10/01/2014                14,068                 6,899                   512                   251
10/08/2014                18,234                 8,942                   663                   325
10/15/2014                23,635                11,591                   860                   422
10/22/2014                30,635                15,024                 1,115                   547
10/29/2014                39,709                19,473                 1,445                   708


End of Month for the Next Year from the End Date

Date        Cases                 Deaths                Daily New Cases       Daily New Deaths      
==========  ====================  ====================  ====================  ====================
09/30/2014                13,556                 6,648                   493                   242
10/31/2014                42,764                20,972                 1,556                   763
11/30/2014               129,996                63,750                 4,729                 2,319
12/31/2014               410,085               201,107                14,920                 7,317
01/31/2015             1,293,657               634,413                47,066                23,081
02/28/2015             3,651,570             1,790,739               132,851                65,150
03/31/2015            11,519,271             5,649,079               419,092               205,524
04/30/2015            35,016,714            17,172,283             1,273,972               624,759
05/31/2015           110,464,001            54,171,820             4,018,881             1,970,869
06/30/2015           335,792,614           164,673,529            12,216,744             5,991,122
07/31/2015         1,059,294,023           519,480,413            38,539,038            18,899,640
08/31/2015         3,341,657,268         1,638,757,001           121,575,553            59,620,953
09/10/2015         4,840,743,028         2,373,912,370           176,115,013            86,367,239

Obviously, there are many factors that will affect these projections. Rather, this model simply projects the number of cases and fatalities based on the current Daily Transmission Rate (DTR), which has been stable for about 3 months. Consider the following other factors that are likely to change the DTR (either for good or for bad) as we move forward from today:

1. Ebola is most easily contained in rural villages which can be easily quarantined.
2. The virus is already spreading in densely populated areas.
3. The virus is most successfully treated in hospitals, but hospitals in the affected areas are already overwhelmed, with Ebola patients already dying in the streets. This will clearly work to increase the Daily Transmission Rate.
4. On the other hand, as more and more aid is sent to West Africa, in the form of well trained personnel, equipment, and supplies, this will work to reduce the DTR.
5. As more people are educated how to avoid contracting and spreading the disease, this will work to decrease the DTR.
6. There are plenty of other factors, including the possibility of a vaccine, better treatment methods, better education, etc., that will influence the DTR over time.
7. The influence of weather on the DTR is unknown, but it is reasonable to assume that the weather will have both a direct and indirect impact on the DTR. The impact may be favorable in some effects, and unfavorable in others.

While the numbers quoted above are grim, they do not yet represent fact. Do not panic, but do not be complacent, either. Any preparations you make to "shelter in place" will serve you well for other contingencies, too.

On the other hand, epidemiologists are already saying that the number of cases is already doubling every two weeks. That means that the numbers I've posted above are actually quite conservative.

This model is contained within a macro-enabled Microsoft Excel 2010 spreadsheet (i.e., a .xlsm file). I would be willing to share it with other Freepers if someone can provide a place to post it for download and can tell me how to sanitize my name from it (again, I don't want my employer to be in any way held accountable for this).

[Dallas59]

I wonder how many Chinese and Arabs fly to and from Africa?

[FES0844]

Frightening.

[ClearCase_guy]

A while ago, I put “30,000 dead by Jan 1 2015” on my wall at work. People thought I was crazy. I guess it turns out I’m an optimist.

[cuban leaf]

I think that just as malaria has a worse DTR in some areas than others, Ebola is kinda the same way. Only with Malaria it is natural environment while with Ebola it’s the “civilization” environment. Just as women tend to be a natural firebreak to Aids (unless engaging in anal sex), civilization is a natural firebreak to Ebola.

[BenLurkin]

Am I reading this correctly? You are projecting close to 5 Billion cases by the end of the next 12 months?

Prayers.

[DouglasKC]

Great analysis...1 to 2 billion dead in a year based on current information is that correct?

[ALASKA]

Wow.......

[Shelayne]

Those are staggering numbers. I am praying...

[Ray76]

You could place the spreadsheet on dropbox.com. It’s no charge. After upload there’s an option to click to get a url that you can give to others so that they do not have to signup with dropbox, makes sharing ez.

[ZOOKER]

Other factors which could affect transmission rate-

Political factors, such as the a mandated quarantine, bans on travel to affected areas, closing of borders/airports

Mutation of the virus which affect its ease of transmission or lethality

[DannyTN]

I think yours is high. A month ago when the spread rate was 5% increase per day, I was projecting 200,000 in 90 days. But the most recent week showed a spread rate of 3% which would put us at 69,000 by Dec 12th.

Basic formula that I’m using is:
Current Cases * (SpreadRate)^#DaysOut)

Still a very serious crisis. One that the WHO has been criminally negligent in responding to.

[DannyTN]

I think yours is high. A month ago when the spread rate was 5% increase per day, I was projecting 200,000 in 90 days. But the most recent week showed a spread rate of 3% which would put us at 69,000 by Dec 12th.

Basic formula that I’m using is:
Current Cases * (SpreadRate)^#DaysOut)

Still a very serious crisis. One that the WHO has been criminally negligent in responding to.

[scouter]

Am I reading this correctly? You are projecting close to 5 Billion cases by the end of the next 12 months?

Only if the current Daily Transmission Rate holds that long and if the current reported numbers represent 75% of the true numbers. There are many factors that could increase (bad) or decrease (good) that rate.

In fact, I do not believe it will pan out that badly. There are many, many, things that will work together to lower the DTR. And a small change in the DTR can have a huge effect on the projections. But this is presented as a warning to those who are pooh-poohing the issue. The math doesn't lie.

And I'm glad that you picked up on the key word: projecting, not predicting.

[Vermont Lt]

Thanks for your summary. I appreciate the efforts.

Kind of a downer right before dinner though.

[Slyfox]

Thanks and Yikes!

[Vermont Lt]

The only other thing I would consider are the non-Ebola increased death rate.

It is to be expected that caregivers will be hit hard, and early. Follow on deaths would skyrocket. For example: cancer patients, cardiac, and other first responder issues that would normally be treated.

I would guess that mortality rate will tick up another 5-10% above norm because of this.

[Slyfox]

Kind of a downer right before dinner though.

Don't you remember the good old days when you would read about something like this every few months or so?

Now, it is on a daily basis.

Before long it will be hourly.

[UCANSEE2]

PING

[Axenolith]

Don’t forget possible intentional spread...