Empirical evidence for the effect of airline travel on inter-regional influenza spread in the United States.

Full Abstract

BACKGROUND:
The influence of air travel on influenza spread has been the subject of numerous investigations using simulation, but very little empirical evidence has been provided. Understanding the role of airline travel in large-scale influenza spread is especially important given the mounting threat of an influenza pandemic. Several recent simulation studies have concluded that air travel restrictions may not have a significant impact on the course of a pandemic. Here, we assess, with empirical data, the role of airline volume on the yearly inter-regional spread of influenza in the United States.

METHODS AND FINDINGS:
We measured rate of inter-regional spread and timing of influenza in the United States for nine seasons, from 1996 to 2005 using weekly influenza and pneumonia mortality from the Centers for Disease Control and Prevention. Seasonality was characterized by band-pass filtering. We found that domestic airline travel volume in November (mostly surrounding the Thanksgiving holiday) predicts the rate of influenza spread (r(2) = 0.60; p = 0.014). We also found that international airline travel influences the timing of influenza mortality (r(2) = 0.59; p = 0.016). The flight ban in the US after the terrorist attack on September 11, 2001, and the subsequent depression of the air travel market, provided a natural experiment for the evaluation of flight restrictions; the decrease in air travel was associated with a delayed and prolonged influenza season.

CONCLUSIONS:
We provide the first empirical evidence for the role of airline travel in long-range dissemination of influenza. Our results suggest an important influence of international air travel on the timing of influenza introduction, as well as an influence of domestic air travel on the rate of inter-regional influenza spread in the US. Pandemic preparedness strategies should account for a possible benefit of airline travel restrictions on influenza spread.

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Author information

Author/s: Brownstein, John S (JS); Wolfe, Cecily J (CJ); Mandl, Kenneth D (KD);

Affiliation: Children's Hospital Informatics Program at the Harvard-MIT Division of Health Sciences and Technology, Boston, Massachusetts, USA. john_brownstein(-atsign-)harvard.edu

Grants: 2TA5 LM07092–11 (Agency:NLM NIH HHS) ; R01 LM007677–01 (Agency:NLM NIH HHS) ; R21 LM009263–01 (Agency:NLM NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: PLoS medicine (PLoS Med), published in United States. (Language: eng)

Reference: 2006-Sep; vol 3 (issue 10) : pp e401

Dates: Created 2006/11/29; Completed 2006/12/26; Revised 2008/11/20;

PMID: 16968115, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

Comments and Corrections

CommentIn: PLoS Med. 2006 Nov;3(11):e503; author reply e502. (PMID: 17132057)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Aircraft
Centers for Disease Control and Prevention (U.S.)
Disease Outbreaks
Fourier Analysis
Humans
Influenza, Human - epidemiology; mortality; transmission

Models, Theoretical
Seasons
Sentinel Surveillance
Time Factors
Travel - statistics & numerical data
United States - epidemiology

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