Influenza in travellers.

Area of Science:

• Epidemiology
• Travel Medicine
• Infectious Diseases

Background:

• The role of travel in influenza transmission has been highlighted by recent pandemics.
• Understanding the seasonal spread of influenza remains incomplete.

Purpose of the Study:

• To review the incidence of influenza in febrile travelers.
• To assess the effectiveness of vaccination in this population.
• To identify key factors contributing to travel-related influenza spread.

Main Methods:

• Review of studies on febrile travelers returning from subtropical and tropical regions.
• Analysis of vaccination status and influenza incidence.
• Evaluation of the impact of air transportation on disease spread.

Main Results:

• Influenza incidence in returning febrile travelers ranged from 5% to 15%.
• No significant difference in incidence was observed between vaccinated and unvaccinated travelers in reviewed studies.
• Air travel, especially long-haul flights, is a primary driver of influenza spread, with travel restrictions proving ineffective for pandemic prevention.

Conclusions:

• Influenza must be considered in any febrile traveler, regardless of respiratory symptoms.
• Future research should incorporate shorter incubation periods for more accurate travel-related influenza incidence estimates.
• Availability of vaccines from opposite hemispheres and optimized vaccine efficacy in the elderly and immunocompromised are crucial.