Mapping population and pathogen movements

Abstract

For most of human history, populations have been relatively isolated from each other, and only recently has there been extensive contact between peoples, flora and fauna from both old and new worlds. The reach, volume and speed of modern travel are unprecedented, with human mobility increasing in high income countries by over 1000-fold since 1800. This growth is putting people at risk from the emergence of new strains of familiar diseases, and from completely new diseases, while ever more cases of the movement of both disease vectors and the diseases they carry are being seen. Pathogens and their vectors can now move further, faster and in greater numbers than ever before. Equally however, we now have access to the most detailed and comprehensive datasets on human mobility and pathogen distributions ever assembled, in order to combat these threats. This short review paper provides an overview of these datasets, with a particular focus on low income regions, and covers briefly approaches used to combine them to help us understand and control some of the negative effects of population and pathogen movements.

Keywords: Disease; Migration; Mobility; Modelling; Travel.

Figure 1.

The spatial (x-axis) and temporal (y-axis) scales of human movements and the datasets available to quantify them (a) pre-21st century and (b) today.

Figure 2.

Changing global connectivity and mobility through air travel. The international commercial air network in (a) 1933 (adapted from Massey), and (b) 2010.

Figure 3.

Levels of migration between districts in Senegal 1997–2002, derived from census microdata. The thickness of each migration line represents the total number of migrants between districts, with migration quantified by a change of residence within the 1997–2002 period.

Figure 4.

A screenshot taken from the Vector-borne Disease Airport Importation Risk tool (VBD-Air: www.vbd-air.com), highlighting direct flight routes to London Heathrow from Plasmodium falciparum endemic areas, with each route shaded by the amount of air traffic. The underlying map shows the distribution of P. falciparum prevalence. The output of the tool highlights how well connected ‘malaria-free’ countries such as the UK are to endemic regions through air passengers. The UK receives around 2000 notified imported malaria cases a year.