Serological evidence of subclinical transmission of the 2009 pandemic H1N1 influenza virus outside of Mexico

Day Yu Chao, Kuang Fu Cheng, Tsai Chung Li, Trong Neng Wu, Chiu Ying Chen, Chen An Tsai, Jin Hwa Chen, Hsien Tsai Chiu, Jang Jih Lu, Mei Chi Su, Yu Hsin Liao, Wei Cheng Chan, Ying Hen Hsieh

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Background: Relying on surveillance of clinical cases limits the ability to understand the full impact and severity of an epidemic, especially when subclinical cases are more likely to be present in the early stages. Little is known of the infection and transmissibility of the 2009 H1N1 pandemic influenza (pH1N1) virus outside of Mexico prior to clinical cases being reported, and of the knowledge pertaining to immunity and incidence of infection during April-June, which is essential for understanding the nature of viral transmissibility as well as for planning surveillance and intervention of future pandemics. Methodology/Principal Findings: Starting in the fall of 2008, 306 persons from households with schoolchildren in central Taiwan were followed sequentially and serum samples were taken in three sampling periods for haemagglutination inhibition (HI) assay. Age-specific incidence rates were calculated based on seroconversion of antibodies to the pH1N1 virus with an HI titre of 1:40 or more during two periods: April-June and September-October in 2009. The earliest time period with HI titer greater than 40, as well as a four-fold increase of the neutralization titer, was during April 26-May 3. The incidence rates during the pre-epidemic phase (April-June) and the first wave (July-October) of the pandemic were 14.1% and 29.7%, respectively. The transmissibility of the pH1N1 virus during the early phase of the epidemic, as measured by the effective reproductive number R0, was 1.16 (95% confidence interval (CI): 0.98-1.34). Conclusions: Approximately one in every ten persons was infected with the 2009 pH1N1 virus during the pre-epidemic phase in April-June. The lack of age-pattern in seropositivity is unexpected, perhaps highlighting the importance of children as asymptomatic transmitters of influenza in households. Although without virological confirmation, our data raise the question of whether there was substantial pH1N1 transmission in Taiwan before June, when clinical cases were first detected by the surveillance network.

Original languageEnglish
Article numbere14555
JournalPLoS One
Volume6
Issue number1
DOIs
Publication statusPublished - 2011
Externally publishedYes

    Fingerprint

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Chao, D. Y., Cheng, K. F., Li, T. C., Wu, T. N., Chen, C. Y., Tsai, C. A., Chen, J. H., Chiu, H. T., Lu, J. J., Su, M. C., Liao, Y. H., Chan, W. C., & Hsieh, Y. H. (2011). Serological evidence of subclinical transmission of the 2009 pandemic H1N1 influenza virus outside of Mexico. PLoS One, 6(1), [e14555]. https://doi.org/10.1371/journal.pone.0014555