  In spite of the considerable progress towards reducing illiteracy rates, many
countries, including developed ones, have encountered difficulty achieving
further reduction in these rates. This is worrying because illiteracy has been
related to numerous health, social, and economic problems. Here, we show that
the spatial patterns of illiteracy in urban systems have several features
analogous to the spread of diseases such as dengue and obesity. Our results
reveal that illiteracy rates are spatially long-range correlated, displaying
non-trivial clustering structures characterized by percolation-like transitions
and fractality. These patterns can be described in the context of percolation
theory of long-range correlated systems at criticality. Together, these results
provide evidence that the illiteracy incidence can be related to a
transmissible process, in which the lack of access to minimal education
propagates in a population in a similar fashion to endemic diseases.
