Univariate analysis of variables associated with the number of poliomyelitis outbreaks in Africa from 1 January 2004 to 31 December 2010.

n = 622 from 56 countries.aNo tourists were reported from Nigeria for nine countries, all of which are comparatively small in population size. To include these countries in the analysis 0.5 was added to the number of tourists before multiplying by the incidence in Nigeria and log-transforming the data.