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Published on: February 25, 2013
Descriptive Analysis of Measles Transmission Among Travelers During Domestic and Inbound US International Air Travel,
Karla C Bagley1, Jennifer J Fowler1, Alida M Gertz1
1Karla C. Bagley, MBS, MPH, is a Port Health Protection Officer; Jennifer J. Fowler, DVM, MPH, is an Epidemiologist; Alida M. Gertz, MD, DrPH, MPH, MSc, DTM&H, is a Port Health Medical Officer and Team Lead for Support, Evidence, Analytics, & Liaison Team; Argelia Figueroa, MSc, and Kayla M. Lavilla, MPH, are former Epidemiologists; Francisco Alvarado-Ramy, MD, FACP, is a Captain, US Public Health Service Commissioned Corps, and Chief Medical Officer, Travel Risk Assessment and Mitigation Branch; Clive M. Brown, MBBS, MPH, MSc, DTM&H, FRSPH, FASTMH, is Branch Chief, Port Health Protection Branch; Sundari Mase, MD, MPH, is Branch Chief, Travel Risk Assessment and Mitigation Branch; and Shannon L. Gearhart, MD, MPH, is Aviation Activity Lead and Port Health Medical Officer; all in the Division of Global Migration Health, National Center for Emerging and Zoonotic Infectious Diseases. Adria Mathis, MSPH, is an Epidemiologist, and David Sugerman, MD, MPH, FACEP, is a Captain, US Public Health Service Commissioned Corps, and Team Lead for Measles, Rubella, and CMV; both in the Division of Viral Diseases, National Center for Immunization and Respiratory Diseases. All of the authors are with the Centers for Disease Control and Prevention, Atlanta, GA.
Abstract:
Measles is highly transmissible and can lead to severe complications and mortality risk. Cases of measles are reportable to the US Centers for Disease Control and Prevention (CDC). This study describes characteristics of travelers who flew while infectious with measles and their contacts. We analyzed data from domestic and US inbound international flights reported between January 1, 2018, and December 31, 2019. To identify contacts potentially exposed to measles during air travel we used the CDC-defined measles contact zone and crossmatched with the CDC measles database. We conducted a descriptive analysis of travelers with measles and their aircraft contacts and determined average time from flight exposure to contact interview. During the analysis period, CDC received reports of 83 air travelers infectious with measles resulting in 5,186 potential aircraft exposures. Health departments provided data to CDC for 39% (n=2,037) of the exposures/contacts. On average, 9.8 days elapsed between flight exposure and initial interview attempt. Of the 2,037 contacts interviewed, 82% (n=1,680) reported a history of vaccination or prior disease. Seven secondary cases were identified. Five were exposed on US inbound international flights, 5 had no history of vaccination, and 4 were seated outside the contact zone. Most contacts who developed measles were unvaccinated and shared a US inbound international flight with an infected traveler. Over half of secondary cases were outside the contact zone. The average first contact interview attempt occurred beyond the 3-day window for effective prophylaxis. Continued emphasis on measles vaccination, evaluation of the contact zone definition, and timely contact investigation of exposed travelers may prevent secondary cases and outbreaks in the United States.
Insights
Measles outbreaks can occur from infectious air travelers. Most secondary cases were unvaccinated individuals on international flights, often outside the defined contact zone, highlighting the need for timely interventions.
Area of Science:
- Public Health
- Epidemiology
- Infectious Disease Control
Background:
- Measles is a highly contagious viral illness with significant morbidity and mortality risks.
- Air travel facilitates the rapid global spread of infectious diseases like measles.
- The US Centers for Disease Control and Prevention (CDC) mandates measles case reporting.
Purpose of the Study:
- To characterize measles-infected air travelers and their exposed contacts.
- To analyze the effectiveness of the CDC's measles contact zone definition.
- To identify factors contributing to secondary measles transmission during air travel.
Main Methods:
- Analysis of domestic and international flight data (2018-2019) for infectious measles travelers.
- Identification of potential contacts using the CDC measles contact zone.
- Descriptive analysis of traveler and contact data, including interview timelines.
Main Results:
- 83 infectious measles travelers were reported, leading to 5,186 potential exposures.
- Only 39% of contacts were interviewed, with an average delay of 9.8 days post-exposure.
- Seven secondary cases were identified; most were unvaccinated and exposed on international flights, with some cases occurring outside the standard contact zone.
Conclusions:
- Unvaccinated individuals on international flights are at high risk for measles transmission.
- The current contact zone definition may not capture all exposed individuals.
- Timely contact investigation and robust measles vaccination are crucial for preventing outbreaks.
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