“Low humidity during the winter enables the influenza virus to live longer indoors, and this together with spending more time indoors and in closer contact, significantly increases the risk of transmission and infection,” Dr. Hassad wrote in MedPage Today.
Furthermore, both the influenza virus and the SARS-CoV-2 virus that causes Covid-19 have a fatty outer membrane that keeps them structurally sound and protects the RNA they contain that infects cells, causing disease. In temperatures at or near freezing, this fatty membrane solidifies into a gel, forming a rubbery coat that helps the virus survive and move more readily from person to person in cooler weather.
Characteristics of our own nasal passages in the colder, drier months enhance the risk of infection by these viruses. Nasal passages become dry and more susceptible to damage when the humidity is low, making it easier for viruses to invade the body.
These factors, along with “a high level of transmissibility (including asymptomatic transmission) and virulence of SARS-CoV-2, create a perfect recipe for an even more explosive pandemic” in the coming months, Dr. Hassad noted. Given the fact that the vast majority of people have no immunity to Covid-19, he wrote, it “has the potential to parallel the 1918 flu pandemic if we fail to comply with the protective measures recommended by public health authorities.”
Dr. Stanley M. Perlman, a microbiologist at the University of Iowa who has studied coronaviruses for more than four decades, said in an interview that the “key variables” for a new explosion of Covid infections “are people spending time indoors in not well-ventilated places and not wearing masks.” While air exchange in a hospital unit takes place 12 times an hour, indoor air in a typical room in a private home is exchanged only once or twice an hour, on average.
Dr. Perlman emphasized, “This is a remarkably contagious virus. Things have gotten worse and will get worser still. Our biggest worry is Covid-19 fatigue. People are losing respect for the virus and letting their guard down, which is a bad idea.” Even outdoors, he said, “if you’re standing one foot away from someone and not wearing a mask,” you could transmit or contract the virus.
“The nose and mouth are the virus’s portal of entry,” Dr. Hassad said. “How can a mask not be a barrier against an organism coming toward me? There’s been an obvious difference in infections where masks are being worn consistently. It’s common sense, and it’s not a huge burden.”