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Pre-symptomatic transmission of pandemic influenza H1N1 2009: investigation of a family cluster, Brazil

  • F. T. M. FREITAS (a1), A. P. S. CABRAL (a1), E. N. C. BARROS (a1), M. J. O. BURIGO (a2), R. D. PROCHNOW (a2), L. A. SILVA (a2), M. A. WIDDOWSON (a3) and J. SOBEL (a3)...

We investigated the first cluster of pandemic influenza H1N1 2009 reported in Brazil in May 2009. The index case-patient had travelled from the USA and had contact with 11 relatives before she presented with symptoms. We conducted face-to-face or telephone interviews with the index case-patient and all suspect cases. We found evidence of pre-symptomatic transmission of the virus to four of her contacts. This finding has public health implications because it indicates that viral transmission in communities may not be prevented solely by isolating symptomatic case-patients.

Corresponding author
*Author for correspondence: F. T. M. Freitas, Secretaria de Vigilância em Saúde, Ministério da Saúde, Setor Comercial Sul, Quadra 4, Bloco A, 2° andar,70304-000, Brasilia, Brazil. (Email:
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1.Patrozou E, Mermel LA. Does influenza transmission occur from asymptomatic infection or prior to symptom onset? Public Health Reports 2009; 124: 193196.
2.Carrat F, et al. Time lines of infection and disease in human influenza: a review of volunteer challenge studies. American Journal of Epidemiology 2008; 167: 775785.
3.Gu Y, et al. Pandemic (H1N1) 2009 transmission during presymptomatic phase, Japan. Emerging Infectious Diseases 2011; 17: 17371739.
4.Hermes J, et al. Lack of evidence for pre-symptomatic transmission of pandemic influenza virus A (H1N1) 2009 in an outbreak among teenagers; Germany, 2009. Influenza and Other Respiratory Viruses 2011; 5: e499503.
5.Brazilian Ministry of Health. Protocol of notification and investigation of influenza A H1N1 ( Accessed 5 June 2009.
6.Sheat K. An investigation into an explosive outbreak of influenza – New Plymouth. Communicable Disease New Zealand 1992; 92: 1819.
7.Fraser C, et al. Factors that make an infectious disease outbreak controllable. Proceedings of the National Academy of Sciences USA 2004; 101: 61466151.
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Epidemiology & Infection
  • ISSN: 0950-2688
  • EISSN: 1469-4409
  • URL: /core/journals/epidemiology-and-infection
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