Well, the first patient to come down with Ebola in America
has now led to the first person to contract Ebola in America. Meanwhile, another 50 people are being
monitored to see if they come down with the disease. Great.
Just great.
The strain of the Ebola virus that is currently burning
through much of west Africa, and has now been brought to both Europe and
America, has a lethality rate of about 50%.
That is, one out of every two people who catch the virus end up dying
from the infection. The survivors, even
though they are immune to reinfection, may have serious long term health
problems from the disease. It’s too
early to tell how serious that will be.
Government pronouncements that Ebola was not going to come
to this country were, of course, ridiculous. The latency period of Ebola can be up to 21
days. That is, from the time the virus
gets into your system to the first symptoms appearing can be as little as two
days, or as many as three weeks. Airport
screening protocols will not be effective at keeping out people who show no
symptoms.
So a rational person would assume that more infected people
will cross our borders. That’s the bad
news. The good news is that you are not
infectious during the latency period.
You can only infect other people once you display symptoms. After the onset of symptoms, starting with
fever and sore throat, you stay infectious until one of two things happens: a)
you get better, or b) your remains are cremated after you die.
How bad the US outbreak will be is based on a concept called
the Basic Reproduction Number, or R0.
What R0 boils down to is the average number of new people infected by
each person with the disease. With the
current outbreak in West Africa, R0 is running about 2. Each new case ends up infecting two
more. This doesn’t sound so bad, until
you realize that the number of patients is doubling about once a month. So you start with one patient, who becomes
two, who become four, who become eight, and so on. This kind of pattern gets really scary after
about ten doublings.
At two to the tenth power, 4096 people are currently
infected. With a periodicity of one
month (figure average of 15 days of latency, followed by 15 days of
infectiousness), at the end of one year, 16384 people have caught the virus in
the last month. One year later, over 16
million new cases come up at the two-year anniversary of the start of the
outbreak. Six months later, you get a
billion new cases in the last month. If
R0 was to stay at 2, within three years half of the world’s population will be
dead, and the survivors will all be immune.
On the other hand, if R0 can be kept below 1, than the
outbreak dies off. Given that the first patients
to contract the disease in both the US and Europe are health care workers,
presumably trained to follow anti-contamination protocols, I’m not as confident
about the situation as the CDC’s pronouncements would have one believe.
So let’s review.
Lethal disease? Check. You can be infected, and still act normal for
a time? Check. Death does not make you non-infectious, and
indeed makes you more dangerous to the living than ever? Check. So basically, we’re in the early days of the
Zombie Apocalypse.