Ebola update — summary of the CDC announcement on the afternoon of 9/30/2014.
The patient arrived in Dallas on 9/20. His symptoms became severe enough for him to seek medical care on 9/30. The first priority of the CDC is the patient’s health. Secondly, they are trying to locate everyone he contacted in that 10 day period. The CDC will monitor all his contacts for 21 days.
What does this actually mean?
According to eMedTV (link at bottom of article), Ebola has an incubation period of 2-21 days, on average it’s 4-6 days. That’s how long it takes before you show the first symptoms. And the big kicker — a patient is infectious during the incubation period.
That means our Liberian guest was probably infectious for 5 to 10 days of his 10 days in Dallas. He might have contacted quite a few people in that amount of time. Ebola is like sexually transmitted diseases (STDs) chlamydia, gonorrhoea, or syphilis, only easier to catch. The standard epidemiological formula for STDs is for every person contacted there are 20 additional people who may have been exposed. And that also means for each of those 20 there are another 20, and so on.
Think of it like the old penny trick where you give someone twice as many pennies each day as the previous day. The Doubling Penny trick takes only 30 days to reach 5 million dollars.
Now do the math for the spread of contagious disease at a multiple of 20 instead of 2. After 30 days there are more than a billion exposures. Not everyone who is exposed will contract the disease and a lot of those exposures are likely to be second, third, or more, but Ebola is killing thousands, perhaps tens of thousands in Africa. With an estimated 90% fatality rate according to WebMD we can expect the major disaster in Africa to continue for some time.
Without immediate action we can certainly expect Ebola to spread … here … now. No disease faced by humanity has posed such an existential threat since the Black Plagues of the Middle Ages which killed millions across Europe, Asia, and Africa.
[Update 10/1/2014] It was announced today on ABC news that there are now 12 to 18 people under monitoring in Dallas including 5 school children. Apparently the infected man visited four area schools before his second attempt to seek medical help. The children are being kept at their homes. The disposition of the adults under monitoring was not specified.