As “Covid Winter” approaches, especially in states with seasonal changes such as New York, it calls into question what this will mean for the virus in the coming months. When thinking about when the pandemic will end, temperature, humidity, and seasonal shifts are large factors which work against stopping the spread of the virus. Externally, as the air outside becomes colder, it is able to hold less water vapor, which decreases humidity. HVAC (heating, ventilation, and air conditioning) units inside office buildings work by taking in outside air and heating it to channel through the indoor space, which similarly dries the air out.
Why is humidity important in preventing the spread of the virus on a biological level? In an aerosol study conducted at Virginia Tech, the researches demonstrated that as humidity levels decrease, the particles of moisture released from actions such as talking, coughing, sneezing become smaller. This becomes a problem because the dry air causes the water in the molecules to evaporate faster, therefore becoming even smaller and staying in the surrounding air for a longer period of time. Any droplets can then travel around the closed, indoor space further. Their minuscule size allows them to be inhaled and move deeper into the lungs, where, as we learned in the video we watched in class, a spike on the virus will insert into a receptor molecule on a healthy cell membrane, allowing it to infect the healthy lung cell, leading to a susceptible person contracting COVID-19 and being able the virus further.
Other coronaviruses, like the common cold, influenza, and rhinoviruses, have exhibited similar spreading patterns dictated by the seasons, demonstrated by flu season occurring in the winter, calming down in summer, and coming back again in fall. Scientists believe COVID-19 could do the same, and are currently conducting research and gathering data to see the correlation between the virus and humidity levels. Stephanie Taylor, a physician and fellow at Har-
vard Medical School, is part of a joint study with the Massachusetts Institute of Technology that “found that the most powerful correlation between national numbers of daily new coronavirus cases and daily Covid-19 deaths was indoor relative humidity.” In reflecting upon their findings, she says that humidity “is so powerful, it’s crazy.”
The only way to know exactly how the coming winter months will affect the spread of the virus is through time and observation, but it is interesting to look at the biological processes and movement of particles in relation to humidity to understand how the virus may have an increased spread as it becomes colder. I also feel this background helps us be able to make intelligent, informed decisions about the risk of social gatherings as it becomes harder to stay outdoors and the weather changes. What do you think is lying ahead in “Covid Winter?” Do you think we will inevitably have to wait until the humidity changes in spring to declare an official end to the pandemic?