****
**** Unanswered questions about the spread of Ebola
****
There has been very little Ebola spread out of the three
countries in West Africa. This has led me to wonder if perhaps
I was missing something.
The World Health Organization publishes Ebola Situation Reports
every few days.
I went to the
most recent situation report (PDF), dated October 25, 2014. The
following table depicts the total numbers of infections and deaths:
Code:
+---------------+--------------+--------- +
| Country | # infections | # deaths |
+---------------+--------------+--------- +
| Guinea | 1553 | 926 |
| Liberia | 4665 | 2705 |
| Sierra Leone | 3896 | 1281 |
| Mali | 1 | 1 |
| Nigeria | 20 | 8 |
| Senegal | 1 | 0 |
| Spain | 1 | 0 |
| U.S. | 4 | 1 |
+---------------+--------------+--------- +
| Total | 10141 | 4922 |
+---------------+--------------+--------- +
IT seems strange that the only large numbers of cases are in the
original countries (Guinea, Liberia, Sierra Leone), and that the only
cases outside of Africa were in Spain and U.S. It doesn't make sense
to me that Ebola hasn't spread to other countries in Africa, and that
there haven't been individual cases in other countries in Europe or
Asia or Latin America.
****
**** Comparing the Ebola location maps
****
So, in order to do further analysis, I went back WHO's original
original situation report (PDF), dated August 29, 2014, and I
compared some of the numbers in the two reports, in order to
get an estimate of the growth rate in the number of cases.
If you take the total number of infections -- 3052 on August 29, and
10141 on October 25 -- and do a computation, then you get that the
number of infections doubles every 4.7 weeks, which is a little more
than a month (4.25 weeks per month).
If you apply this rate to the number of infections, you get 40K by Jan
1, 80K by Feb 1, 160K by Mar 1, and so forth. But can that doubling
rate be sustained? The WHO announcement that the outbreak is "in
decline" would seem to indicate that it can't be sustained.
So next, I extracted the Ebola location maps from the two reports.
Here's the August 29, 2014, map:
Ebola location map, 29-Aug-2014 (WHO)
Here's the October 25, 2014, map:
Ebola location map, 25-Oct-2014 (WHO)
Comparing these two maps, you can see that most infections were in the
west, but they've apparently been moving eastward, apparently stopping
at the borders of Mali and Côte d'Ivoire. This is not credible.
These country borders are porous, and tribal boundaries do not
correspond to national boundaries. It's not credible that the spread
of Ebola has stopped dead at these country borders.
We recently had the news story of the two year old infected baby who
was carried on a bus all the way from Liberia to the western border of
Mali almost to the eastern border, with multiple stops, including a
two-hour stop in Bamako. Other than the death of the 2 yo, we haven't
heard anything more about Ebola in Mali. (
"25-Oct-14 World View -- Two-year-old baby in Mali dies after spreading Ebola"
)
At least a few cases of Ebola must surely have spread into these Mali
and Côte d'Ivoire, on the border with Liberia, without our being aware
of it. If this is true -- and I don't see how it could not be true --
then there must be unreported cases in these countries.
If there are individual cases in the U.S. and Spain, then there must
be unreported individual cases in other countries. Consider
the following:
- Cuba has sent hundreds of medical professionals to West
Africa. - China has thousands of workers in the region.
If there have been Ebola cases in the U.S. and Spain, it's hard to
believe that Cuba and China would be immune to Ebola cases. What's
different about Cuba and China is that if either has an outbreak of
Ebola in either country, it would be covered up and we'd never know,
until the outbreak became extremely serious. (This is what happened
in China with the SARS outbreak ten years ago.)
There are plenty of people, including migrant workers, who go back and
forth between Africa and their home countries, including Asia and
Latin America. Some countries are so undeveloped that officials might
not even know there's an Ebola outbreak until it had spread for
several days.
So there are a lot of unanswered questions about what's going on.
There must be or will be many unreported cases of Ebola, in West
Africa and elsewhere; it's not credible to believe otherwise.
Finally, returning to the question of whether the Ebola outbreak is
"in decline," one possibility is that it's really in decline, and
another possibility is that the only thing that's declining is the
number of reporting cases, with sharp increases in the number of
unreported cases. We should have definite answers by the end of the
year.
WHO Ebola Situation Reports
KEYS: Generational Dynamics, World Health Organization, WHO,
Bruce Aylward, Guinea, Liberia, Sierra Leone, Spain,
Cuba, China
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