Airport Screening Unlikely To Prevent Spread Of SARS Or Influenza

In the event of a new SARS or influenza epidemic, air travel wouldrepresent the principal route of international spread. Although airportentry screening has been advocated, its benefit is currently unknown.

Using the incubation periods for influenza and SARS,researchers at the Health Protection Agency estimated the proportion ofpassengers with latent infection who would develop symptoms during anyflight to the UK.

For SARS, they found that the incubation period was too long toallow more than a small proportion of infected individuals to developsymptoms during a flight to the UK (0-3% for European flights and amaximum of 21% for the longest flights from East Asia).

Although influenza has a much shorter incubation period thanSARS, the average predicted proportion of people infected withinfluenza and progressing during any flight was still less than 10%.

Because the proportion of individuals detected is highest fromcities with the longest flight duration, screening passengers from theFar East and Australasia derives the most benefit. But, even then, thesensitivity for cities in these areas would still be low, explain theauthors.

Early screening is unlikely to be effective in preventing the importation of either SARS or influenza, they conclude.

Although adopting a policy of quarantining all exposedpassengers on the detection of a single case could substantiallyincrease the benefit of entry screening, this still leaves the problemthat the sensitivity of entry screening is low.