Wednesday, October 15, 2014

Tracking Ebola

The “Ebola Infection Projector” Excel workbook available for download from was built using CDC data from the current West African outbreak available as of October 12th, 2014.

Three caveats are required.  
  1. Although I've had a long career in health care as a hospital chief executive officer and at one time served as director of planning for 17-county health systems agency, I am neither a clinician nor an epidemiologist and make no claim of expertise in those areas. That said, the download provided here treats this as a math problem (which it is) and makes no attempt to diagnose or apply clinical knowledge of any type.
  2. Although I have a high level of confidence in the workbook's calculations, they are only as good as that “official” information upon which they are based. The workbook does show why it is so important to stop virus transmission in the population in the very early stages before it goes parabolic.
  3. Finally, given the government's propensity for lying, I am withholding judgment on the validity of the outbreak and believe everyone should approach "official information" about the outbreak and its course with a great deal of healthy skepticism.
The workbook contains three worksheets. 
  1. The sheet behind the first tab (“Input and Summary Table”) allows you to input different transmission rates cell B6 (the number in shown in red font just opposite “Number infected By Each New Patient”). The number currently entered in this cell is the reported West African transmission rate as of October 12th, 2014.
  2. The worksheet behind the second tab (“Ebola Time Line Detail”) plots the number of infected people and deaths forward at ten day intervals based on the transmission rate entered in cell B6 on the “Input and Summary Table” worksheet.
  3. The third sheet (“U.S. Ebola Projections”) graphs the result. The course of the outbreak will ultimately be determined by the transmission rate. Change the value in Cell B6 on the “Input and Summary” worksheet behind the first tab to project different potential outcomes.
Guinea, Liberia, and Sierra Leone differ from the United States in countless and profound ways. Basic sanitation in West Africa ranges from hideous to non-existent. Those West African nations are also very poor and the population is not highly mobile. The rate of transmission will be significantly affected by those differences. We should have the edge in the sanitation category. However, because West African roads are bad, there aren’t that many cars, and the West African population doesn’t fly a lot, transmission of the virus is apt to be comparatively localized. On the other hand, the U.S. population travels a great deal using mass transit and cross-continent air transport. That’s not a plus in terms of containing an outbreak.
It is also important to remember that the current observed transmission rate is based on a very small sample. We really don’t know (and neither does the CDC) how many actual cases there have been. It may be an entirely different number than what is being reported, either because of a real absence of accurate information or deliberate news (panic) management.
It should also be remembered that we’re talking about “average” transmission rates. At the early stages of an outbreak, this can vary tremendously in a short span of time. The more days that elapse between the diagnosis of Patient “0” and any given date, the better the chances of an accurate projection. It may be months before enough data are available to generate a statistically defensible projection. That said, the user can follow changes in the transmission rate by adjusting the transmission rate input until the result on the “Ebola Time Line Detail” work sheet matches the officially reported U.S. infections and deaths on any given date. You can then observe projected changes in the outbreak’s course over time

May God have mercy on us all.


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