II. Lessons Learned

Supplement E: Managing International Travel-Related Transmission Risk

Public Health Guidance for Community-Level Preparedness and Response to Severe Acute Respiratory Syndrome (SARS) Version 2/3

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During the 2003 global response, the control strategy for the United States included issuing travel notifications,1 distributing health alert notices to travelers arriving from areas with SARS, and conducting visual inspections of arriving travelers to facilitate early identification of imported cases and response to reports of ill passengers. CDC staff met more than 11,000 direct and indirect flights from SARS-affected areas and distributed more than 2.7 million health alert notices to arriving passengers as well as to persons arriving at 13 U.S. land border crossings near Toronto and departing passengers bound for the United States from the Toronto airport. Health alert notices informed returning travelers of potential exposure to SARS-CoV. They alerted travelers to the symptoms of SARS-CoV disease and advised them to promptly seek medical attention if symptoms develop. The notices also provided information and instructions for physicians.

Travel Alerts and Travel Advisories

  • Travel alerts and advisories are notifications of an outbreak of disease occurring in a geographic area. Atravel alert, a lower-level notice, provides information about the disease outbreak and informs travelers how to reduce their risk of acquiring the infection. An alert does not include a recommendation against nonessential travel to the area.When the health risk for travelers is thought to be high, a travel advisory recommending against nonessential travel to the area is issued. Travel advisories are intended to reduce the number of travelers to high-risk areas and the risk for spreading disease to other areas.
  • CDC issues travel alerts and advisories based on evidence of transmission, spread of disease, and effectiveness of local prevention efforts. The quality of local disease surveillance and the accessibility of medical care are additional considerations.

During the outbreak response, CDC quarantine staff met planes reporting an ill passenger to facilitate 1) evaluation of the passenger for possible SARS-CoV disease, 2) collection of locating information on the other passengers, and 3) coordination with federal and local authorities. If the ill passenger was determined to be a possible SARS case, then the locating information was forwarded to state and local health departments for contact tracing.

Border and travel-related activities implemented in countries more seriously affected by SARS included pre-departure temperature and symptom screening, arrival screening (asking passengers about travel history and possible exposure to SARS-CoV), “stop lists” (maintaining lists of persons who were possible SARS cases or contacts to prevent them from traveling), and quarantine of travelers returning from other SARS-affected areas.

Lessons learned from this response support the recommendations included in this Supplement. These lessons included the following:

  • SARS-CoV can spread rapidly on a global scale through international travel if control measures are not implemented.
  • SARS-CoV transmission is usually localized and often limited to healthcare settings and households; the risk of SARS-CoV disease to travelers visiting an affected area is low unless travelers are exposed in these settings.
  • Patients with SARS can transmit infection to other passengers on conveyances and should postpone travel until they are no longer infectious.
  • SARS-CoV transmission can occur within the close confines of conveyances. Resulting infections usually represent a failure to recognize symptomatic index cases and their high-risk contacts, who should have been prevented from traveling.
  • Active follow-up of passengers on conveyances with SARS cases can help prevent further spread by informing passengers of their exposure and providing instructions for monitoring their health and seeking medical evaluation if they become ill.


  1. During the 2003 SARS outbreak, CDC issued two types of travel notifications about disease occurrences in specific geographic areas. A travel alert, a lower-level notice, provided information about the disease outbreak and informed travelers about how to reduce their risk of acquiring the infection. When the health risk for travelers was thought to be high, CDC issued a travel advisory recommending against nonessential travel to the area. Travel advisories were intended to reduce the number of travelers to high-risk areas and the risk for spreading disease to other areas. The levels of notification have since been revised to include four types of travel notices: In the News, Outbreak Notice, Travel Health Precaution, and Travel Health Warning.

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