Estimation of Basic Reproductive Number of Flu-like Syndrome in a Primary School in Iran

INTRODUCTION: Iran, similar to other countries, had faced H1N1 flu outbreak in 2009. In order to assess its transmission dynamic, we estimated its force of infection (β) and basic reproductive number (R(0)). METHODS: Within a middle size primary school in Iran, we actively followed students and detected flu-like syndrome among students and their families in the first three months of academic year; October through December 2009. We estimated the probability of disease transmission within families (β) fitting random effects Poisson regression model. Moreover, R(0) within the school was computed based on the number of detected cases. RESULTS: In 452 students, 204 influenza-like syndromes were detected. The estimated β within families was 0.10; increasing one infectious member within each family was associated with 30% increase in this number. The estimated R(0) for the first month was 1.21 (95% C.I.: 0.99, 1.47); corresponding numbers for the first two and first three months were 1.28 (95% C.I.: 1.05, 1.54) and 1.32 (95% C.I.: 1.11, 1.59), respectively. CONCLUSION: It seems that the dynamic transmission of H1N1 virus was more or less comparable with that in other seasonal species. Our findings showed that the virus mainly circulated among students within schools. In addition, it seems that the transmission rate within families was relatively high.