The waiting time for inter-country spread of pandemic influenza
Date
2007-01-03
Authors
Caley, Peter
Becker, Niels
Philp, David
Journal Title
Journal ISSN
Volume Title
Publisher
Public Library of Science
Abstract
BACKGROUND: The time delay between the start of an influenza pandemic and its subsequent initiation in other countries is highly relevant to preparedness planning. We quantify the distribution of this random time in terms of the separate components of this delay, and assess how the delay may be extended by non-pharmaceutical interventions.
METHODS AND FINDINGS: The model constructed for this time delay accounts for: (i) epidemic growth in the source region, (ii) the delay until an infected individual from the source region seeks to travel to an at-risk country, (iii) the chance that infected travelers are detected by screening at exit and entry borders, (iv) the possibility of in-flight transmission, (v) the chance that an infected arrival might not initiate an epidemic, and (vi) the delay until infection in the at-risk country gathers momentum. Efforts that reduce the disease reproduction number in the source region below two and severe travel restrictions are most effective for delaying a local epidemic, and under favourable circumstances, could add several months to the delay. On the other hand, the model predicts that border screening for symptomatic infection, wearing a protective mask during travel, promoting early presentation of cases arising among arriving passengers and moderate reduction in travel volumes increase the delay only by a matter of days or weeks. Elevated in-flight transmission reduces the delay only minimally.
CONCLUSIONS: The delay until an epidemic of pandemic strain influenza is imported into an at-risk country is largely determined by the course of the epidemic in the source region and the number of travelers attempting to enter the at-risk country, and is little affected by non-pharmaceutical interventions targeting these travelers. Short of preventing international travel altogether, eradicating a nascent pandemic in the source region appears to be the only reliable method of preventing country-to-country spread of a pandemic strain of influenza.
Description
Keywords
Keywords: airborne infection; article; controlled study; disease course; epidemic; human; infection prevention; infection risk; influenza; mass screening; pandemic; time; travel; virus strain; virus transmission; disease transmission; Influenza virus A; risk factor
Citation
PLoS ONE 2.1 (2007): e143
Collections
Source
PLOS ONE (Public Library of Science)
Type
Journal article
Book Title
Entity type
Access Statement
License Rights
Restricted until
Downloads
File
Description