Global transport networks and infectious disease spread

Abstract

Air, sea and land transport networks continue to expand in reach, speed of travel and volume of passengers and goods carried. Pathogens and their vectors can now move further, faster and in greater numbers than ever before. Three important consequences of global transport network expansion are infectious disease pandemics, vector invasion events and vector-borne pathogen importation. This review briefly examines some of the important historical examples of these disease and vector movements, such as the global influenza pandemics, the devastating Anopheles gambiae invasion of Brazil and the recent increases in imported Plasmodium falciparum malaria cases. We then outline potential approaches for future studies of disease movement, focussing on vector invasion and vector-borne disease importation. Such approaches allow us to explore the potential implications of international air travel, shipping routes and other methods of transport on global pathogen and vector traffic.

Figure 1

The Old World distribution of Ae. albopictus (dark grey); countries reporting established breeding populations of Ae. albopictus in the last 30 years (middle grey); countries reporting Ae. albopictus interception at ports (light grey). Data sources: Center for International Earth Science Information Network (CIESIN) (http://www.ciesin.org/docs/001-613/map15.gif), supplemented with information from literature sources (Gratz, 2004; Gubler, 2003; Lounibos, 2002; Medlock et al., 2005; Moore, 1999; Moore and Mitchell, 1997).

Figure 2

Counties of the United States of America reporting the presence of Ae. albopictus in 2000. (Adapted from US Centers for Disease Control and Prevention (CDC); URL: http://www.cdc.gov/ncidod/dvbid/arbor/albopic_97_sm.htm.)

Figure 3

(a) Climatic similarity dendrograms for the major seaports of the World and (b) climatic similarity dendrograms for the major airports of the World. In both figures the inset close-up shows the branches of significance to the dispersal of Ae. Albopictus.

Figure 3

(a) Climatic similarity dendrograms for the major seaports of the World and (b) climatic similarity dendrograms for the major airports of the World. In both figures the inset close-up shows the branches of significance to the dispersal of Ae. Albopictus.

Figure 4

Mahalanobis climatic distance from Chiba Port, Japan, for (a) the world and (b) the United States of America. Darker shades represent areas with climates more similar to that of Chiba.

Figure 4

Mahalanobis climatic distance from Chiba Port, Japan, for (a) the world and (b) the United States of America. Darker shades represent areas with climates more similar to that of Chiba.

Figure 5

(a) Graph showing the number of UK imported malaria cases 1977–2002 (Data source: UK Health Protection Agency (UKHPA)); (b) Graph showing the number and type of USA imported malaria cases 1991–2002 (Data source: Shah et al., 2003); (c) Graph showing the acquisition region of USA imported malaria cases 1992–2002 (Data source: Shah et al., 2003); and (d) Graph showing the number of passengers travelling on air routes between the UK and SSA, broken down by SSA region 1997–2003 (Data source: UK Civil Aviation Authority (UKCAA)).

Figure 6

(a) Countries in which confirmed or probable cases of airport malaria have been reported. (b) Month in which suspected European airport malaria cases occurred (where date is provided). (Data taken from Alos et al., 1985; Csillag, 1996; Danis et al., 1996; Giacomini, 1998; Giacomini and Brumpt, 1989; Giacomini and Mathieu, 1996; Giacomini et al., 1995; Gratz et al., 2000; Guillet et al., 1998; Hemmer, 1999; Holvoet et al., 1982; Isaäcson, 1989; Isaäcson and Frean, 2001; Jafari et al., 2002; Karch et al., 2001; Kruger et al., 2001; Lusina et al., 2000; Majori et al., 1990; Mangili and Gendreau, 2005; Mantel et al., 1995; Mouchet, 2000; Praetorius et al., 1999; Shpilberg et al., 1988; Signorelli and Messineo, 1990; Smith and Carter, 1984; Thang et al., 2002; Toovey and Jamieson, 2003; Van den Ende et al., 1996; Whitfield et al., 1984.)

Figure 7

Non-SSA airports that are similar enough climatically to the SSA airports within their primary malaria transmission season for possible P. falciparum-infected Anopheles invasion to occur.