During winter 2020, health officials are predicting the incidence of COVID-19 to increase exponentially.  It is not the cold weather that causes the respiratory disease, but rather, the pathogenic organism SARS-CoV-2. The SARS-CoV-2 virus spreads mainly through interpersonal contact via respiratory droplets and aerosols, especially in enclosed spaces with inadequate ventilation. But what is the mechanism by which cold temperatures facilitate the spread of respiratory infections? It is well established that there is seasonal variation in the incidence of respiratory infections. Similar to seasonal influenza, we are witnessing a rapidly accelerating increase in COVID-19 as we move into the cold season

The Virus Structure

SARS-CoV-2 shares key transmission characteristics with the influenza virus. They are both enveloped viruses, meaning they have an outer fatty or lipid membrane. Research on the influenza virus has shown that this outer fatty membrane solidifies into a gel at temperatures at or below freezing. The thickened membrane may allow the virus to survive in cooler temperatures and move from person to person. So, it is plausible that SARS-CoV-2 will adapt similarly to the cold weather, making the virus hardier and easier to spread. This increases the probability that a potential host or susceptible person will be exposed to the virus.

Humidity Factor

Low humidity also increases evaporation of respiratory viral droplets into smaller aerosol particles that can linger longer in the air, increasing the risk of airborne transmission in the winter. It is plausible that this will increase exposure to a higher viral load during the winter.  Low humidity also leads to drying of the nasal passage, which can increase susceptibility to infection by damaging the nasal mucosa, making it easier for the virus to invade the body.

Indoor Proximity

Other environmental factors driving the accelerated spread of respiratory infections including COVID-19 during winter are increased indoor dwelling and overcrowding. When the virus lives longer indoors due to low humidity and people are spending more time indoors in closer contact, health officials see a significantly increases the risk of transmission and infection.

Vitamin D

Another health factor in mitigating COVID-19 risk is Vitamin D.  It is produced in the skin during exposure to sunlight and has been shown to have a protective effect against respiratory tract infections and is positively correlated with immune health. During winter, due to increased indoor activity and reduced exposure to sunlight, a person’s level of vitamin D may be depleted. Our knowledge of the transmission dynamics of SARS-CoV-2 is still evolving. These factors, along with a high level of transmissibility and virulence of SARS-CoV-2, create a perfect recipe for transmission. The vast majority of the population remains unexposed and therefore susceptible to infection. Our Cornerstone experts can help with your industrial infectious disease programs. Contact us at info@corner-enviro.com for more information.