Swine flu scareTravel ban will not meaningfully slow spread of epidemic

The first instinct of governments when reports arrive of epidemics in other countries, is to restrict travel to these countries. Computer models suggest that such restrictions on international air travel will have little effect on stemming the spread of an influenza pandemic. As the H1N1 strain of swine flu spreads around an increasingly interconnected world, the economic damage caused by border closings and mandatory travel restrictions will do more harm than good, scientists says.

Swine flu has now been confirmed in Mexico, the United States, Canada, Spain, Britain, Germany, Israel, and New Zealand. “There is no real sense in applying strict travel restrictions especially at this stage. It’s not going to help,” says Alessandro Vespignani, a computer scientist at the University of Indiana in Bloomington, whose team is also trying to predict the spread of the current outbreak. The World Health Organization’s (WHO) Emergency Committee also took this position at a meeting on Monday: “WHO does not recommend closing of borders and does not recommend restriction of travel,” said Keiji Fukuda, assistant director general for health security and environment.

New Scientist’s Ewen Callaway writes that Japan, however, which has no reported cases of swine flu thus far, has stopped issuing visas to Mexican nationals. Vespignani says these measures are unlikely to be effective as the swine flu outbreak bounces around the world, potentially requiring more and more restrictions to keep infected travelers outside of the country. If things get bad in a very short time, you will have to cut off communication with the rest of the world, he says. “Shutting down a country is impossible and, more or less, we see that it is not really effective.”

Callaway reports that in a 2007 paper, Vespignani’s team modeled the spread of influenza pandemics of varying severities in 3,100 urban centers in 220 countries. They also looked at the effectiveness of countermeasures including vaccination, administration of antiviral drugs such as Tamiflu, and travel restrictions. A Draconian 10-fold reduction in airline travel would delay a pandemic by only a few weeks and have no effect on its overall health impact, Vespignani’s team concluded. Other measures — particularly widespread administration of antiviral drugs — proved far more effective at limiting the spread of hypothetical pandemics.

A 2006 study led by Ben Cooper at the Health Protection Agency in London suggests that travel limitations would have to be implemented extremely early in a pandemic, when just a handful of people in a city are infected, dramatically to slow the spread. Even with a dramatic 99.9 percent drop in airline traffic, most cities will eventually succumb to an influenza pandemic, Cooper’s models indicate

Another recent study, by John Brownstein et al., of seasonal influenza outbreaks supports the contention that travel restrictions slow the spread of the disease, but not its ultimate toll. Airline travel restrictions after the terrorist attacks on 11 September 2001 delayed the arrival of the 2001-2 flu season in the United States by about two weeks, but had little impact otherwise, says Brownstein, an epidemiologist at Children’s Hospital Boston, Massachusetts, who led that study. “It’s not likely that any amount of travel restriction is going to have a significant impact,” he says of the current swine flu outbreak.

Callaway writes that modelers have also attempted to measure the economic cost of widespread travel bans in response to pandemic flu. In 2007 a team led by Joshua Epstein of the Brookings Institution estimated that a 95 percent reduction in air travel in the United States could cost about $100 billion per year, or a little less than 1 percent of the U.S. gross national product. “In this situation, things are definitely not bad enough to warrant the economic impacts [travel limits] are going to have,” Brownstein says.

-read more in Vittoria Colizza, “Modeling the Worldwide Spread of Pandemic Influenza: Baseline Case and Containment Interventions,” PLoS Med 4, no. 1 (23 January 2007): e13 (doi:10.1371/journal.pmed.0040013); Ben S. Cooper et al., “Delaying the International Spread of Pandemic Influenza,” PLoS Med 3, no. 6 (2 May 2006): e212 (doi:10.1371/journal.pmed.0030212); John S. Brownstein et al., “Empirical Evidence for the Effect of Airline Travel on Inter-Regional Influenza Spread in the United States,” PLoS Med 3, no. 10 (12 September 2006): e401 (doi:10.1371/journal.pmed.0030401); Joshua M. Epstein, “Controlling Pandemic Flu: The Value of International Air Travel Restrictions,” PLoS ONE 2, no. 5 (2 May 2007): e401 (doi:10.1371/journal.pone.0000401)