Risk assessment guidelines for infectious diseases transmitted on aircraft (RAGIDA): Influenza

Public health guidance

European Centre for Disease Prevention and Control. Risk assessment guidelines for infectious diseases transmitted on aircraft (RAGIDA) - Influenza. Stockholm: ECDC; 2014.

This report which is part of the RAGIDA project (Risk Assessment Guidance for Infectious Diseases transmitted on Aircraft) provides viable options for decision-makers when faced with the choice of whether to contact trace air travellers and crew that were potentially exposed to infectious diseases during a flight.

Executive Summary

This technical report provides options for contact tracing approaches related to possible transmission of influenza viruses on aircraft. It is targeted at decision-makers faced with the choice of whether to contact-trace air travellers and crew that were potentially exposed to influenza viruses during a flight, and covers the following:


  • Seasonal influenza
  • Novel influenza virus with pandemic potential, or seasonal influenza virus with increased virulence
  • Influenza virus with zoonotic potential, such as avian or swine influenza


Contact tracing of passengers or crew possibly exposed to an influenza virus on-board an aircraft can have a number of objectives:


  • to slow down the spread of the virus upon introduction into a country/region
  • to facilitate timely diagnosis and treatment, for example, to administer post-exposure prophylaxis
  • to allow implementation of other control measures like isolation
  • to study the characteristics of the virus or assess the epidemiologic situation


When assessing the risk of infection on-board an aircraft, criteria such as the infectivity of the index case, the time since the flight occurred, evidence of transmission in the country of departure and the country of destination, the scale and prioritisation of contact tracing are all important considerations to take into account. 


The document proposes practical algorithms that cover these considerations and assist in making decisions if contact tracing should be pursued and what should its extent be in specific cases.


The proposed contract tracing approach is based on evidence found in scientific literature, combined with the knowledge of a disease-specific expert panel.

More about influenza

Seasonal influenza

Seasonal influenza is a preventable infectious disease with mostly respiratory symptoms. It is caused by influenza virus and is easily transmitted, predominantly via the droplet and contact routes and by indirect spread from respiratory secretions on hands etc.

Avian influenza

Avian influenza is an infectious viral disease mainly found in birds, but under certain circumstances infections can also occur in humans even though the risk is generally very low.