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How does the contagiousness of seasonal influenza compare with that of COVID-19?

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Influenza virus — influenza A colored transmission electron micrograph showing influenza viruses (red) at the outer surface of a host cell.

COVID-19 is significantly more contagious than seasonal influenza.1

The contagiousness of a disease is often measured by its basic reproduction number ( $R_{0}$ ), which represents the average number of people one infected individual will transmit the virus to in a fully susceptible population.2

Seasonal Influenza: The $R_{0}$ for seasonal influenza typically ranges from 1.3 to 1.8, meaning an infected person generally spreads the virus to one or two others.12
COVID-19: The $R_{0}$ for COVID-19 has varied by variant. While the original strain had an $R_{0}$ of 2 to 4, subsequent variants, such as Omicron, have demonstrated much higher transmissibility, with $R_{0}$ values ranging from 8 to 10 or higher.12

Because COVID-19 is more transmissible and often causes more severe illness than seasonal influenza, public health measures such as vaccination, masking, and social distancing remain essential tools for limiting its spread.12