Early Outbreak of 2009 Influenza A (H1N1) in Mexico Prior to Identification of pH1N1 Virus
Open Access
- 31 August 2011
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLOS ONE
- Vol. 6 (8), e23853
- https://doi.org/10.1371/journal.pone.0023853
Abstract
In the aftermath of the global spread of 2009 influenza A (pH1N1) virus, still very little is known of the early stages of the outbreak in Mexico during the early months of the year, before the virus was identified. We fit a simple mathematical model, the Richards model, to the number of excess laboratory-confirmed influenza cases in Mexico and Mexico City during the first 15 weeks in 2009 over the average influenza case number of the previous five baseline years of 2004-2008 during the same period to ascertain the turning point (or the peak incidence) of a wave of early influenza infections, and to estimate the transmissibility of the virus during these early months in terms of its basic reproduction number. The results indicate that there may have been an early epidemic in Mexico City as well as in all of Mexico during February/March. Based on excess influenza cases, the estimated basic reproduction number R0 for the early outbreak was 1.59 (0.55 to 2.62) for Mexico City during weeks 5–9, and 1.25 (0.76, 1.74) for all of Mexico during weeks 5–14. We established the existence of an early epidemic in Mexico City and in all of Mexico during February/March utilizing the routine influenza surveillance data, although the location of seeding is unknown. Moreover, estimates of R0 as well as the time of peak incidence (the turning point) for Mexico City and all of Mexico indicate that the early epidemic in Mexico City in February/March had been more transmissible (larger R0) and peaked earlier than the rest of the country. Our conclusion lends support to the possibility that the virus could have already spread to other continents prior to the identification of the virus and the reporting of lab-confirmed pH1N1 cases in North America in April.This publication has 33 references indexed in Scilit:
- Serological Evidence of Subclinical Transmission of the 2009 Pandemic H1N1 Influenza Virus Outside of MexicoPLOS ONE, 2011
- On epidemic modeling in real time: An application to the 2009 Novel A (H1N1) influenza outbreak in CanadaBMC Research Notes, 2010
- Pandemic (H1N1) 2009 Influenza Community Transmission Was Established in One Australian State When the Virus Was First Identified in North AmericaPLOS ONE, 2010
- Rapid SYBR Green I and Modified Probe Real-Time Reverse Transcription-PCR Assays Identify Influenza H1N1 Viruses and Distinguish between Pandemic and Seasonal StrainsJournal of Clinical Microbiology, 2009
- Estimation of the reproductive number and the serial interval in early phase of the 2009 influenza A/H1N1 pandemic in the USAInfluenza and Other Respiratory Viruses, 2009
- Seasonal transmission potential and activity peaks of the new influenza A(H1N1): a Monte Carlo likelihood analysis based on human mobilityBMC Medicine, 2009
- Use of Cumulative Incidence of Novel Influenza A/H1N1 in Foreign Travelers to Estimate Lower Bounds on Cumulative Incidence in MexicoPLOS ONE, 2009
- Initial human transmission dynamics of the pandemic (H1N1) 2009 virus in North AmericaInfluenza and Other Respiratory Viruses, 2009
- Severe Respiratory Disease Concurrent with the Circulation of H1N1 InfluenzaThe New England Journal of Medicine, 2009
- Pandemic Potential of a Strain of Influenza A (H1N1): Early FindingsScience, 2009