Ebola virus is back, this time in West Africa, with over 350 cases and a 69% case fatality ratio at the time of this writing. The culprit is the Zaire ebolavirus species, the most lethal Ebola virus known, with case fatality ratios up to 90%. The epicenter and site of first introduction is the region of Guéckédou in Guinea's remote southeastern forest region, spilling over into various other regions of Guinea as well as to neighboring Liberia and Sierra Leone.

News of this outbreak engenders three basic questions:

1. What in the world is Zaire ebolavirus doing in West Africa, far from its usual haunts in Central Africa?
2. Why Guinea, where no Ebola virus has ever been seen before?
3. Why now?

We'll have to wait for the outbreak to conclude and more data analysis to occur to answer these questions in detail, and even then we may never know, but some educated speculation may be illustrative.

Authors

Daniel G. Bausch, Lara Schwarz