Face-to-Face: Study Finds Peak Viral Transmission Occurs Within 5 Seconds Interview with:

Prof. Asai Takeshi

Prof. Takeshi

Prof. Takeshi Asai
Faculty of Health and Sports Sciences, University of Tsukuba,
Tsukuba Japan
Faculty of Physical Education, International Pacific University
Okayama, Japan What is the background for this study?

Response: In the early stages of the COVID-19 pandemic, contact and droplet transmission were considered the main routes of infection. However, it was later demonstrated that airborne transmission is an important route. Therefore, accumulating real-world data on airborne transmission was deemed crucial. What are the main findings?

Response:  It is believed that the peak of virus exposure risk during face-to-face passing occurs within 5 seconds.

When feeling the risk of exposure during face-to-face passing in enclosed spaces, stopping breathing or exhaling for 5 seconds during passage suggests a significant reduction in exposure risk. What should readers take away from your report?

Response: Although this experiment targets only simple face-to-face passing, there is a demand for quantitative studies on virus exposure risk during various physical activities, sports, group activities, and the like.

Ventilation was suggested to be highly effective even during physical activity, but since the fluid dynamics of unsteady states like ventilation are highly complex, research from various perspectives will be necessary.


Asai, T., Kurosaki, E., Kimachi, K. et al. Peak risk of SARS-CoV-2 infection within 5 s of face-to-face encounters: an observational/retrospective study. Sci Rep 13, 17520 (2023).

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Last Updated on November 1, 2023 by Marie Benz