Face masks and indoor ventilation were key to control the spread of COVID-19, according to a study published in the journal Physical Reviews. These results provide valuable insights to support future prevention strategies for respiratory diseases.
In 2020, the world came to a standstill as increasing COVID-19 cases triggered lockdowns, travel restrictions, and strict public health measures. The World Health Organisation (WHO) estimates that more than three million people died from the virus during the type forest year of the outbreak, highlighting the devastating toll on global health and the economy.
To better understand the dynamics of airborne diseases and inform future measures, Dr Richard Sear from the University of Surrey, UK, evaluated how the virus spreads during contact and how effective protective measures can reduce the risk.
“I’ve tried to measure how effective strategies, such as mask-wearing, are for the transmission of airborne viruses. This is both for any future pandemic, and for seasonal flu. I combined modelling with data from the UK’s NHS COVID-19 app. While these estimates are highly approximate, they provide guidance on the value of measures such as face masks, social distancing, and improved indoor air quality, which could be tested in the future,” said Dr Sear.
Viral load, ventilation, and individual susceptibility significantly influence COVID-19 transmission rates, but some contacts pose a much higher risk than others. According to Dr. Sear, these findings highlight the importance of addressing environmental and behavioural factors in public health strategies.
The results showed that, in terms of personal protective equipment (PPE), high-quality face masks, such as N95/FFP2, were particularly effective in reducing transmission risk. They decreased the effective reproduction number for COVID-19 transmission by a factor of approximately nine. Using N95 masks lowers transmission risk threefold, no matter the duration of contact, but surgical and cloth masks are much less effective.
We can also use ventilation to control airborne transmission, as viral particles tend to accumulate in poorly ventilated spaces. Increasing ventilation indoors—whether through opening windows and doors or increasing the speed of air conditioning systems—can lower transmission rates by as much as 30%. Complementing good ventilation with physical distancing further reduces the risk.
“The COVID-19 pandemic was terrible for many of us, which is why it’s important that we learn from our experiences. It also demonstrated how quickly we can develop and roll out vaccines when faced with a global health crisis. Moving forward, both we as individuals and our leaders have an opportunity to apply these lessons to better control respiratory diseases – not only to head off any future pandemics, but to also manage seasonal diseases such as flu and RSV,” said Dr Sear.
Sear P (2025) Estimating the population-level effects of nonpharmaceutical interventions when transmission rates of COVID-19 vary by orders of magnitude from one contact to another. Physical Reviews, https://link.aps.org/doi/10.1103/PhysRevE.110.064302