Julien Arino - Understanding More About the Spread of Disease

Julien Arino, Mathematics

Posted 10 November 2009
by Maureen Paisley

The spread of infectious diseases, and most recently, the H1N1 virus, is a hot topic in the media.  Governments, health agencies, and public institutions are all working towards developing pandemic preparedness plans.  Although the focus is now H1N1, concerns about the ease and the rapidity of disease spread were brought into sharp focus for scientists and public health officials during the SARS epidemic. 

In 2003, a previously unknown virus emerged in the Guangdong province of China and rapidly spread around the world through the air transport system.  Canada imported cases of SARS through airports in Vancouver and Toronto, leading to 44 deaths and expenditures exceeding one billion dollars to control the outbreak in Ontario alone.  This case highlighted Canada's vulnerability to global infectious disease threats through air travel, and the BioDiaspora project was initiated to investigate this vulnerability.

Julien Arino, in the Faculty of Science, is the project's lead mathematician in the interdisciplinary team comprising the fields of medicine, infectious diseases, public health, biostatistics, geographic sciences, network analysis, computer sciences and mathematical modeling.  To understand more about the spread of disease by air transport, the team needed to learn more about the air transportation network, and so, they gathered data from various agencies and companies throughout the world.  To get an idea of the scope this project, the data included information involving nearly 4,000 airports as well as a description of more than 97% of the trips taken worldwide - a network that transports more than 2.5 billion passengers each year.  Their data bank includes all flight schedules, actual trips taken with up to 5 connections, real time flight information for half the world, and world tourism and World Bank information.

The task was enormous, but the project's team analyzed data so that they could rapidly assess how global infectious-disease alerts or confirmed epidemics might spread through the commercial transport system worldwide at any point in time. 

In March and April 2009, international air travelers departing from Mexico were unknowingly transporting a new virus, H1N1, to cities around the world.  When the BioDiaspora team members examined the data they gathered from the International Air Transport Association (IATA) for March and April 2008, they found that 2.35 million passengers traveled from Mexico to 1,018 cities in 164 countries, and approximately 80% of these passengers had flight destinations in the United States or Canada.  Further, when the researchers compared the international destinations of travelers departing from Mexico with confirmed cases of H1N1 associated with travel to Mexico, they found a remarkably strong degree of correlation.  The larger the number of passengers headed to a specific destination, the greater the likelihood of infection.

The analysis of world-wide air-traffic patterns can help cities and countries around the world anticipate the risks of importing infectious diseases.  For example, the BioDiaspora team is working in collaboration with the Kingdom of Saudi Arabia to better understand the implications of H1N1 and the pilgrimage, in late November, to Mecca for the Hajj which in 2008 involved 2.5 pilgrims, 1.7 million from outside of Saudi Arabia. 

By examining the risks of importing global infectious diseases the project considers the implications for potential shared responsibilities among nations so that that together they can strengthen public health security worldwide.  The BioDiaspora project is sponsored by the Public Health Agency of Canada and has worked with international agencies including: the US Centre for Disease Control (CDC), the European CDC and the Kingdom of Saudi Arabia.