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Six months after Covid-19 was declared a pandemic, this story is being republished as a reminder of the many things scientists have learned about the disease and how it spreads.
We are in a terrifying and confusing pandemic, with new and sometimes contradictory information about Covid-19 coming up 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 is difficult to keep up. What’s more, people tend to remember the first things they learn about a new topic, a phenomenon called “anchoring bias,” and it is psychologically challenging to replace old information with new knowledge. Here are nine 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.
Covid-19 outbreaks can occur anywhere. In the first months of the pandemic, there were many illusions and altercations (as in: it’s other people’s problem): the Chinese got it because of where they buy their food. Italians succeeded because they greet each other with kisses on the cheeks. Cruise people got it from buffets. People in nursing homes got it because they are fragile. The people of New York got it because the city is crowded. We now know that outbreaks can occur in urban areas, rural areas, suburbs, and in any culture in the world.
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Covid-19 can make anyone sick and kill. The first victims of the pandemic were disproportionately older or had health problems. Age and frailty remain risk factors for serious illness and death, but we now know that disease can kill young, healthy people. It can kill young adults. It can kill teenagers. It can kill children.
Contaminated surfaces are not the main hazard. At first, public health experts advised people to wash their hands frequently (while singing “Happy Birthday” twice), disinfect surfaces, and avoid touching their faces. This was based on studies of how other diseases spread, such as norovirus and the viruses that cause the common cold. It’s still a good idea to wash your hands regularly (and avoid handshakes), but we now know that surfaces are not the primary vector for SARS-CoV-2.
It is in the air. At first, experts thought that the virus was spread mainly through droplets of mucus and saliva that are expelled when people cough or sneeze. They thought these droplets were heavy enough to fall out of the air quite quickly. According to early cases of hospital spread, the virus appeared to be aerosolized, that is, released 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 shed in a variety of droplet sizes, with some particles small enough to persist in the air, especially in poorly ventilated indoor spaces.
Many people are contagious without being sick. Other respiratory diseases cause people to cough and sneeze. The original SARS outbreak made people so sick, so quickly, that most went to the hospital. Controlling the temperature and telling sick people to stay home can prevent symptomatic illnesses from spreading, and in the early months of the pandemic, many countries began screening people at their borders for these cases. But the biggest challenge in stopping SARS-CoV-2 is that many apparently healthy people transmit the disease without symptoms or before symptoms start, simply by talking and breathing.
Hot summer weather will not stop the virus. Influenza is a seasonal respiratory illness that peaks in the winter, and some experts expected the spread of Covid-19 to show a similar, slow pattern in the Northern Hemisphere during spring and summer. We now know that people’s behavior, regardless of the season, is the strongest predictor of whether the disease will spread.
The masks work. When the pandemic began, experts were concerned that the mass purchase of face masks could exacerbate the shortage of personal protective equipment for healthcare workers and others who needed them. They also cautioned that the masks can make people complacent about social distancing and that cloth or paper masks (unlike N95 surgical masks) cannot stop the smallest aerosol viral particles. We now know that masks can greatly reduce the amount of viruses that people expel into the air while talking, and that masks protect the people who wear them, not perfectly, but enough to reduce the transmission of disease.
Racism, not race, is a risk factor. The pandemic should end the misconception that race, a social construct, is a biological explanation for health disparities. Covid-19 has disproportionately killed people of color in the United States. This is not due to genetic differences, but to the systemic racism that has isolated and impoverished many Native Americans and has made Black and Latino people more likely to have “essential” jobs that expose them to infections, a greater burden of stress. and less access to high-quality health care.
Disinformation kills. The president of the United States, other politicians, anti-vaccine activists, and members of the right-wing media have, to their eternal shame, used the pandemic to stoke racism, spread misinformation and amplify conspiracy theories. His supporters have threatened health officials, including Tony Fauci and his family; refused to wear masks; refused to cooperate with contact tracers; and rejected proven basic public health advice on social distancing. Rep. Louie Gohmert, who refused to wear a mask on Capitol Hill and reportedly discouraged his staff and interns from wearing masks, tested positive for SARS-CoV-2 and is being treated with hydroxychloroquine, a drug that Trump has endorsed but failed in clinical trials. Trump supporter Herman Cain died of Covid-19 on July 30, weeks after attending a rally in Tulsa without a mask. Calls to poison control centers increased after Trump speculated that injecting or ingesting disinfectants could protect against the coronavirus. Preliminary evidence suggests that people who watched Fox News were more likely to downplay the pandemic, making the spread worse. The most important public health measure during a pandemic of a disease without a cure or vaccine, as many countries around the world that have controlled the virus have shown, is to help experts share clear, reliable, accurate and actionable information based on the best evidence. Spreading lies has spread this disease.
Read more about the Coronavirus outbreak from Scientific American here. And read the coverage of our international magazine network here.
