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Pandemic A/H1N1 influenza: transmission of the first cases in Spain

Laura Català1, Cristina Rius, Patricia García de Olalla

  • 1Parc de Salut Mar-Universitat Pompeu Fabra-Public Health Agency of Barcelona, Spain. lcatala@aspb.es

Enfermedades Infecciosas Y Microbiologia Clinica
|September 16, 2011
PubMed
Abstract

Insights

The first pandemic A/H1N1 influenza cases in Spain were imported from Mexico. Public health interventions helped lower transmission rates below initial estimates.

Area of Science:

  • Epidemiology
  • Virology
  • Public Health

Background:

  • The 2009 pandemic A/H1N1 influenza strain emerged in Mexico, necessitating an understanding of its international spread.
  • Investigating the initial cases in Spain was crucial for identifying Europe's first transmissions of this novel influenza strain.

Purpose of the Study:

  • To determine the attack rate of the pandemic A/H1N1 influenza virus among early cases in Spain.
  • To analyze the factors contributing to the international spread of the virus.
  • To identify the first instances of influenza transmission within Europe.

Main Methods:

  • Studied three groups related to an overseas flight: 71 students, 94 other passengers, and 68 confirmed case contacts.
  • Calculated the attack rate and 95% confidence intervals (CI) for the student and contact groups.
  • Implemented preventive measures on April 26th, 2009, following the notification of the first cases.

Main Results:

  • The first confirmed pandemic A/H1N1 influenza cases in Spain involved three students returning from Mexico.
  • One student was responsible for the first indigenous case in Spain and one of Europe's earliest cases.
  • Similar attack rates were observed in the student group (14.1%; CI: 12.1-16.1) and their contacts (13.2%; CI: 4.4-22.0).
  • No cases were detected among other passengers, indicating a low transmission risk during air travel.

Conclusions:

  • Pandemic A/H1N1 influenza was initially imported into Spain via air travel from Mexico.
  • Implemented preventive measures were effective in reducing primary and secondary transmission rates below World Health Organization (WHO) initial estimates.

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