Excerpted From Scientific American
We’re in a terrifying and confusing pandemic, with new and sometimes conflicting information about COVID-19 emerging all the time. In the early days, a lot of public health advice was based on what we knew about previous disease outbreaks. But this new coronavirus behaves in unexpected ways, and it’s hard to keep up. What’s more, people tend to remember the first things they learn about a new subject, a phenomenon called "anchoring bias," and it’s psychologically challenging to replace old information with new knowledge. Here are some of the most important things we’ve learned about SARS-CoV-2 in the past seven months and why we didn’t fully understand or appreciate them at first.
Outbreaks of COVID-19 can happen anywhere. There was a lot of wishful thinking and othering (as in: it’s those other people’s problem) in the first months of the pandemic: Chinese people got it because of where they buy their groceries. Italian people got it because they greet each other with kisses on the cheeks. People on cruise ships got it because of the buffets. People in nursing homes got it because they are frail. People in New York got it because the city is crowded. Now we know that outbreaks can happen in urban areas, rural areas, suburbs and any culture around the world.
COVID-19 can sicken and kill anyone. The first victims of the pandemic were disproportionately older or had existing health conditions. Age and frailty are still risk factors for serious disease and death, but we now know the disease can kill young and healthy people. It can kill young adults. It can kill teenagers. It can kill children.
Contaminated surfaces are not the main danger. Early on, public health experts advised people to wash their hands frequently (while singing “Happy Birthday” twice), disinfect surfaces and avoid touching their face. This was based on studies of how other diseases spread, such as norovirus and viruses that cause the common cold. It’s still a good idea to wash your hands regularly (and avoid handshakes), but now we know that surfaces aren’t the main vector for SARS-CoV-2.
It is in the air. At first, experts thought the virus was spread primarily through globs of mucus and saliva expelled when people cough or sneeze. They thought these droplets were heavy enough to drop out of the air fairly quickly. Based on early cases of hospital spread, the virus seemed to be aerosolized—that is, lofted into the air in particles small enough to float—only by certain medical procedures such as placing someone on a ventilator. But we now know that the virus is expelled in a range of droplet sizes, with some particles small enough to persist in the air, especially in indoor, poorly ventilated spaces.
Many people are infectious without being sick. Other respiratory diseases make people cough and sneeze. The original SARS outbreak made people so sick, so quickly, that most of them went to the hospital. Temperature checks and telling sick people to stay home can stop symptomatic diseases from spreading, and in the first months of the pandemic, many countries started screening people at their borders to detect these cases. But the biggest challenge for stopping SARS-CoV-2 is that many apparently healthy people spread the disease without symptoms or before symptoms start, simply through talking and breathing.
Warm summer weather will not stop the virus. Influenza is a seasonal respiratory disease that peaks in the winter, and some experts hoped the spread of COVID-19 would show a similar pattern and slow in the Northern Hemisphere during the spring and summer. Now we know that people’s behavior, regardless of season, is the strongest predictor of whether the disease will spread.
Masks work. When the pandemic began, experts worried that mass mask-buying could exacerbate shortages of personal protective equipment for health care workers and others who needed them. They also warned that masks might make people complacent about social distancing and that cloth or paper masks (unlike N95 surgical masks) can’t stop the smallest aerosolized viral particles. Now we know that masks can greatly reduce the amount of virus that people expel into the air while speaking, and that masks protect people who are wearing them—not perfectly, but enough to reduce transmission of the disease.
