Thanks to the wealth of information the WHO is now posting on a (seemingly) weekly basis, I have a new Ebola chart I’d like to share with y’all:
By breaking cases and deaths down by country, it becomes quickly apparent that regional statistics about the outbreak (i.e., 888 cases total, 61% CFR) don’t tell the whole story on their own. Upon closer inspection, a couple of interesting trends appear:
1. While Guinea takes the lead in total [confirmed, probable, & suspected] case count (n = 409), Sierra Leone is not too far behind (n = 337).
2. Case fatality rates across countries are not consistent with one another: Guinea = 76%, Liberia = 62%, and Sierra Leone = 42%.
These two phenomena are partly due to differential (non-concurrent) introduction of EBOV across the three countries currently affected. Right now, the general consensus is that the 2014 West Africa outbreak originated in Guinea with subsequent spread into Liberia in late March. Despite early suspicions, Sierra Leone remained free of confirmed cases until late May.
It’s possible that because Sierra Leone is still relatively new to the scene of the outbreak, its death toll has yet to catch up with its case tally… However, time between onset of symptoms and death is typically 7 to 14 days, so this caveat may only fully apply to cases that have been reported in the last two weeks or so – though delays in reporting may also be to blame. Even more peculiar is how rapidly Sierra Leone seems to have accumulated cases – the vast majority of which have been lab-confirmed (88%). This is especially intriguing given that Liberia reported EBOV-positive cases a full two months prior to Sierra Leone, and yet has only reported 142 total [confirmed, probable, & suspected] cases – 42% of Sierra Leone’s current tally.
So… What’s going on in Sierra Leone? I’m personally still mulling this one over, but I want to know what you think… Send in your #SWAGs (scientific wild-ass guesses) at [firstname.lastname@example.org] or tweet me!