Spread of a Novel Influenza A (H1N1) Virus via Global Airline Transportation

Abstract

The flight itineraries for all passengers departing from commercial airports in Mexico between March and April 2009 were analysed using data from the International Air Transport Association to show how travellers - and consequently to predict how H1N1 - would disseminate worldwide during the initial wavefront of this epidemic. Analysis showed that in March and April 2008, a total of 2.35 million passengers flew from Mexico to 1018 cities in 164 countries. A total of 80.7% of passengers had flight destinations in the USA or Canada; 8.8% in Central America, South America, or the Caribbean Islands; 8.7% in Western Europe; 1.0% in East Asia; and 0.8% elsewhere. The international destinations of travellers departing from Mexico were compared with confirmed H1N1 importations associated with travel to Mexico, and a remarkably strong degree of correlation was found. Of the 20 countries worldwide with the highest volumes of international passengers arriving from Mexico, 16 had confirmed importations association with travel to Mexico as of 25 May 2009. A receiver-operating-characteristic (ROC) curve plotting the relationship between international air-traffic flows and H1N1 importation revealed that countries receiving more than 1400 passengers from Mexico were at a significantly elevated risk for importation. With the use of this passenger threshold, international air-traffic volume alone was more than 92% sensitive and more than 92% specific in predicting importation, with an area under the ROC curve of 0.97.