Kia Hall and Yaneer Bar-Yam, The potential for increase in global Ebola transmission during end of year Liberian holiday travel, New England Complex Systems Institute (October 2014).
The 2014 Ebola outbreak has killed five thousand as of the end of October. While infections have primarily been in Guinea, Sierra Leone and Liberia, land travel has brought cases to Senegal and Mali, and air travel has brought them to Nigeria and the US. Cases in the US have arisen through both normal travel of an individual and unsupervised travel of a returning care provider. This does not include cases that were transferred under strict quarantine to the US and Europe for treatment. Current screening protocols that measure traveler temperature at airports do not prevent infected individuals from traveling because of the long latent period, considered to be 2-21 days, in which symptoms do not appear. Concerns exist that the travel of additional individuals will lead to additional risk of spreading and the threat that the Ebola outbreak will become a global pandemic. Here we analyze the historical seasonal variation in travel and point out that in the case of Liberia, the months of September and October represent a low period for travel to the US. Travel increases in December and January due to the holiday season, as Liberia is a primarily Christian country and family members travel to Africa for the holidays, increasing the risk of additional cases.
Seasonal variation of the number of travelers from Liberia to the US, based upon data from September 2010 through March 2014.