Why Should the United States Feel a Duty to Help West Africa Fight Ebola?

Most people think of America as the antithesis of a colonial power.  But in fact we did have a sort of colony in Africa.  During the mid-19th century, the American Colonization Society moved ~13,000 American settlers to a colony on the  Liberian coast.  This effort was publicly supported by American political giants such as Abraham Lincoln, James Monroe, and Henry Clay, and it received public federal funding.  The colony site was scouted out by a US Naval Vessel, the colony organized itself under US Laws, and it adopted a Constitution based on that of the US.  Today an estimated 5% of the Liberian population is descended from settlers that came from America.  This is why you hear place names in Liberia such as Monrovia (named after President Monroe), Maryland County, Buchanan, and the JFK Medical Center.  If any independent country in the world has strong enough ties with the US to hope for assistance during an emergency, that country is Liberia.

Ebola has historically occurred in very rare, self-limiting outbreaks, mostly in rural villages  in Central Africa.  A key difference in the currrent Ebola epidemic is that it is spreading in crowded, poor, urban areas.  The conditions that are present in Liberia are mirrored in many, many other poor urban areas in Africa, Asia, South and Central America.  At the current caseload of 18,000 - 40,000, Ebola has already spilled out of Guinea, to Sierra Leone and Liberia, and thence in limited quantities to Nigeria, Senegal, Spain, the US, and Mali.  During the early phase of the epidemic, unimpeded by effective international intervention, the disease spread exponentially.  In Sept WHO reported that since May 2014, the number of new cases of Ebola has been doubling every 20-30 days.  In September the CDC put out a worst-case scenario projection of 1.4 million cases by January.