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).

[combat_boots]

Kudos

http://www.thegatewaypundit.com/2014/09/research-model-predicts-1-1-million-to-2-3-million-ebola-deaths-by-september-2015/

[Doc91678]

I wonder how many South African illegal aliens coming into America through our Southern borders have been contaminated with the Ebola virus? At this point the virus is only transferred by contact. If it matures into an aerosol type virus then we do have a problem. Will quarantine then work?

[Daffynition]

U.S. State Department alone putting out a bid for 160,000 suits

*We're from the government and here to help ourselves.*

[Max in Utah]

B F L

[piroque]

marked for later....Thanks for the post

[Black Agnes]

Actually I’d believe that Liberia has lost 50% of its medical personnel.

Nigeria has lost a handful of people at this point. God willing that’s all they’ll lose.

Liberia though is a horror show.

[Black Agnes]

Where they’ll share communal footbaths. And communal germs. And then return back to whence they came.

Including the ones who Hajj from the US.

[Tilted Irish Kilt]

Black Agnes:" Liberia though is a horror show."

I haven't seen any WHO/CDC statistical projections lately , have you ?

[scouter]

I’m sorry. CFR is Case Fatality Rate, to calculate number of deaths.

I used the reported fatality rate as of 9/10/14. The model allows me to adjust this for people who have contracted ebola within the last 3 weeks (and are included in the reported cases number), but have not yet died. In the adjustment, I apply the same fatality rate to these recent cases, but divide by two, assuming that of all the recent cases, half of those who will die have already done so.

[Excellence]

A friend’s favorite saying is, “In the end, the bacteria wins.” Of course this is a virus, but it applies.

[exDemMom]

I have not heard a reasonable explanation why the “developed” world would have a lower rate of transmission. Better sanitation of course, but that sure doesn’t seem to prevent the transmission of the common cold.

We have a better health care system, and are able to keep patients quarantined while tests are run to determine if they do have Ebola (if they have the travel history to suggest such testing is worthwhile). In the hospital, we practice good infection control measures.

An even more important factor is that we do not have the customs that they have in Africa. When someone dies, it is not part of our funeral custom to stroke or lay hands on the dead body to say good-bye. Nor do families wash the bodies or give them enemas while preparing them for burial, all of which are customs in Africa. Many of the Ebola cases happened through touching dead bodies at funerals.

[exDemMom]

What if someone developes symptoms after going through airport screening and/or medical testing , and is among the masses of the Hajj when symptoms show ?

Don't you beleive that the Islamo-facists/ISIS is already aware of the potential destruction that could be wrought world-wide ?

I'm sure that if they show up at a Saudi hospital with symptoms and travel history, they will be quarantined until the Saudi officials can rule out Ebola.

I can only speak to the medical/biological aspects of Ebola, within the context of a natural outbreak. I cannot say anything about the intentional spread of disease by terrorists.

[Cementjungle]

I think it’s crazy that there are still flights out of East Africa to the rest of Africa, Europe, Mideast, and NA.

A lot of flights had been cancelled, but the WHO has been putting a lot of pressure to keep flights operating. Same deal with some neighbors (Senegal for example) who wanted to close borders. WHO has been pushing to keep borders open.

Don't know if that' still the case, but that's what was going on a couple of weeks ago.

[null and void]

The game of Ebola Roulette continues...

*click* spin *click* spin *click* spin…

Eeeee-bolllll-aaaaaa ping!

Bring Out Your Dead

We’re gonna need

a bigger cart!

Post to me or FReep mail to be on/off the Bring Out Your Dead ping list.

The purpose of the “Bring Out Your Dead” ping list (formerly the “Ebola” ping list) is very early warning of emerging pandemics, as such it has a high false positive rate.

So far the false positive rate is 100%.

At some point we may well have a high mortality pandemic, and likely as not the “Bring Out Your Dead” threads will miss the beginning entirely.

*sigh* Such is life, and death...

[XEHRpa]

The problem is that early symptoms are similar to many other flu-like symptoms and might therefore not be immediately recognized. That’s one issue. Another is that, while not airborne, there is the issue of fomites, which are viral particles left on surfaces through human contact. A contagious person uses a door handle. Others that follow and touch that handle are at risk. I also hear that WHO was considering revising the period of contagiousness, to include some pre-symptomatic period... but I can’t find that link at the moment.

[exDemMom]

Tell that to the nurse that got Ebola from the Liberian/US diplomat then passed it on to a patient in the hospital while she was not symptomatic. We are being told a lot of things to keep people from panicking that are not adding up to truth.

While I understand the need to keep the public calm some of the lies just help the spread.

Are you talking about Patrick Sawyer? When he entered the hospital, he seemed to have malaria, and was treated for it. However, he had Ebola, the diagnosis of which was delayed because of the initial diagnosis of malaria. It was during that time that his caregivers were exposed. I am not aware of any secondary transmission events that occurred in the complete absence of symptoms.

Typically, patients become more contagious as the disease progresses. I just read the account of one of the doctors who treated Mr. Sawyer, who had physical contact with her parents before being taken to the hospital. She was quite worried that she had passed the disease to them, but she did not.

[exDemMom]

The problem is that early symptoms are similar to many other flu-like symptoms and might therefore not be immediately recognized. That’s one issue. Another is that, while not airborne, there is the issue of fomites, which are viral particles left on surfaces through human contact. A contagious person uses a door handle. Others that follow and touch that handle are at risk. I also hear that WHO was considering revising the period of contagiousness, to include some pre-symptomatic period... but I can’t find that link at the moment.

The reason it took several months for the Ebola outbreak to even be recognized was the non-specific nature of the early symptoms. That, and Ebola had never been seen in Guinea before. Malaria and Lassa are both common there, and have similar symptoms--IIRC, health officials thought they were dealing with Lassa, which can also have a hemorrhagic presentation.

The transmissibility of Ebola through fomites is an open question. The studies that would determine how long the virus remains infectious on various surfaces under various conditions have not been done. I have not heard anything about a revision of thought about the contagious period.

[ElenaM]

So your CFR is 50%, which I think is at the extreme low end, but at this point the CFR isn’t certain.

Thanks!

[ElenaM]

I have my son-in-law, active duty Army, listening for any “odd” orders, any hint that the military is being activated for in-country deployment. If that happens, my doors close in 72 hours and no one comes in until I am confident that the problem either didn’t exist (false alarm) or it has burned out.

Alternatively, when I hear that a confirmed case exists anywhere east of the Mississippi, the doors close in 72 hours. My daughter and granddaughter will be here by then and we can wait it out. My husband will probably continue to go to work but he’s agreed to stay with family closer to the city if it comes to that.

I guess everyone has to decide for themselves when it’s the right time to hunker down. I’m sure everyone’s predicate is different. The predicates I’ve selected mean I have a greater chance of being wrong but I’m okay with that. I’d rather be wrong and have my children living than be right and six feet under.

[Thud]

Gadsden1st,

Scouter's projection is just a spreadsheet. We've never seen Ebola loose in a major urban area before, where it could easily spread at double Scouter's projected rate.

IMO the issue for the US is vaccine availability. We must have 40-50 million Ebola vaccine units available right when Ebola hits a critical mass here - say about 100,000 victims - or it's national lockdown time for a month. What the indications of that would be is anybody's guess.

The trigger point for me panicking is when people are dying in the streets of Lagos, Nigeria, and not being immediately picked up. At that point Ebola will go worldwide even given widespread vaccine availability in the developed countries, and even the developed countries will suffer economic and financial catastrophe.