Hawaii rated
in top 1%
of air hubs

A study of networks finds
the islands' "centrality" key
in tracing illness outbreaks

WASHINGTON » Honolulu is in the top 1 percent of the world's most vital air travel hubs -- and therefore one of the key places to watch during a contagious disease outbreak, according to a new study.

"If you want to stop something like (SARS), in what places will you want to be sure to monitor individuals? Honolulu would be one of those places, due to its centrality." Luis Amaral Lead researcher

The study by Northwestern University researchers lists Paris as the most important global air connection point.

Coming in a surprising second was Anchorage, Alaska, followed by London, Singapore and New York.

Hawaii ranked 24th among the 3,883 communities with airports around the world. The results of the study are being published in today's issue of Proceedings of the National Academy of Science.

The air transportation network is like the Internet, the study concluded, with networks and hubs funneling traffic around the world.

The findings are important in understanding the flow of travelers and in studying the potential movement of new diseases, said lead researcher Luis Amaral.

Though London and Singapore have far more direct flights with other cities, smaller hubs like Honolulu and Anchorage rank with the big boys due to a vital measure called "centrality" -- a rating of the shortest paths connecting any two cities that involve a transfer at a particular city.

Anchorage, for example, has nonstop flights to just 39 other cities, far fewer than the 242 cities connected to London nonstop.

But Anchorage beats London on centrality because the Alaskan capital serves as a conduit between international routes and smaller, local airports.

Likewise, Honolulu ranks 99th on the number of nonstop links to other cities, but is in the top 25 most vital airports partly because it funnels traffic to and from the neighbor islands, boosting its centrality rating.

Amaral said such hubs also are among the first places that authorities should look when trying to arrest the spread of contagious illnesses such as SARS.

"If you want to stop something like that, in what places will you want to be sure to monitor individuals? Honolulu would be one of those places, due to its centrality," Amaral said.

The analysis also could help regulators determine airports where more competition is needed, and could even shed light on the functions of biological networks within the human body, according to Amaral, an associate professor in the Department of Chemical and Biological Engineering.

A traveler can get from any of the cities to any other with an average of 4.4 flights, and more than half the communities are connected with four flights or fewer, the researchers found.

The most difficult air route? Getting from Mount Pleasant in the Falkland Islands to Wasu, Papua-New Guinea, requires 15 separate flights.

Paris and London benefit from their nation's colonial pasts, with many flights from Africa and Asia going to those cities, where travelers transfer to other planes.

Indeed, they are the top cities in the world for nonstop flights to other places. Paris leads, with flights to 250 other cities, followed by London, 242; Frankfurt, 237; Amsterdam, 192 and Moscow, 186.

The two busiest airports in the United States are in Chicago and Atlanta. The study ranked Chicago 13th on the worldwide centrality list and sixth for nonstop flights, with connections to 184 cities. Atlanta ranked 29th for centrality and eighth in connections, with flights to 172 cities.

The study analyzed 531,574 flights operated by 800 airlines worldwide from Nov. 1 to 7, 2000. While the data are four years old, the researchers say the current worldwide airport network is virtually identical to the one at that time.

The research was funded by the National Institutes of Health.