Figure 6: Maps of the simulated spread of influenza viruses via live swine trade flows.

Simulated spread of an influenza virus from five seed countries (shaded in black) to 146 countries for which live swine trade is available from the United Nations Commodity Trade Statistics Database (available at http://comtrade.un.org) (a–e). The probability (prob.) of an outbreak in the invaded country is shaded from white (probability of 0) to red (probability of 1). The probability of co-invasion by both a virus seeded in North America (Canada and the United States) and Europe also is shaded from white (probability of 0) to red (probability of 1; f). Arrows represent the direction of viral dissemination for countries with a probability of an outbreak >0.25 (see Supplementary Table 5 for a complete list of all outbreak probabilities by country).