Higher Levels of CO2 Increases Survival and Transmission Risk of Viruses in the Air, Study Reveals

For the first time, a new study has revealed the vital role played by CO2 in determining the lifespan of airborne viruses, particularly the pathogen that causes COVID-19.

Transmission of COVID-19 Virus

Inhaling respiratory aerosol containing the severe respiratory syndrome coronavirus-2 (SARS-CoV-2) has been recognized as a vital transmission route in spreading COVID-19. Like other respiratory viral infections, a sufficient dose must be delivered to an infected individual's respiratory system to transmit the disease.

In the case of COVID-19, this is associated with inhaling a sufficient quantity of aerosolized and infectious SARS-CoV-2 particles. Because of this, it is essential to understand the environmental factors that affect the inhalable viral load over time and how they contribute to assessing the transmission risk.

Generally, most non-pharmaceutical interventions conducted to mitigate the risk of viral transmission focus on removing the infectious aerosolized virus from a given space. By reducing the number of virus-containing particles, experts can physically lower the aerosolized viral load.

Since 2020, monitors have become common as an indicator of potential risk of SARS-CoV-2 transmission. Carbon dioxide is a proxy for overall ventilation efficiency, so it is a predictor of total aerosol viral load.

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Understanding Viral Transmission Based on CO2 Levels

Just recently, scientists from the University of Bristol investigated how carbon dioxide significantly prolongs viruses' lives in tiny droplets that circulate in the atmosphere. This represents a huge breakthrough in understanding how and why this happens and what can be done to stop it.

Dr. Allen Haddrell, Senior Research Associate in Aerosol Science, led the study. The details of the experiment are discussed in the paper "Ambient carbon dioxide concentration correlates with SARS-CoV-2 aerostability and infection risk."

It is widely known that SARS-CoV-2 spreads through the air we breathe, just like other viruses. However, the study suggests that opening a window may be more powerful than initially thought, especially in crowded and poorly ventilated rooms. This is because fresh air has a lower concentration of carbon dioxide and causes the virus to become inactivated much faster.

During the COVID-19 pandemic, CO2 monitors helped estimate ventilation in establishments since both carbon dioxide and SARS-CoV-2 are present in exhaled breath. This study has uncovered how carbon dioxide makes the virus survive longer in the air. The researchers also discovered that SARS-CoV-2 variants have various aerostabilities, with the latest 'Omicron' variant having an extended lifespan.

These discoveries were made using unique bioaerosol technology developed by the research team. Known as Controlled Electrodynamic Levitation and Extraction of Bioaerosols onto a Substrate (CELEBS), the technology measures the survival of different SARS-CoV-2 variants in laboratory-generated airborne particles that resemble exhaled aerosol.

By varying the concentration of carbon dioxide in the air between 400 ppm and 6,500 ppm, the scientists confirmed a correlation between increases in carbon dioxide concentrations and the length of time airborne viruses remain infectious and increase the risk of transmission.

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