9 Things Experts Have Learned About Covid-19 So Far
The disease has not changed, but scientific understanding has evolved dramatically By Roy Britt, Published in Elemental, your life, sourced by science. A new Medium publication about health and wellness.



Photo: LEREXIS/Getty Images

The first documented case of Covid-19 in the United States was reported half a year ago, days before early warnings from the U.S. Centers for Disease Control and Prevention (CDC) that a “very serious public health threat” loomed. Yet health officials had only a rough idea of how the novel coronavirus spread, who the disease affected most, and how to best combat transmission and provide treatment.

Public messaging on the seriousness of the virus was at times conflicting and confusing, including the early advice not to wear masks. Six months later, scientists have a firm handle on how the virus spreads and what should be done to get the pandemic under control.

Here are nine things we know about Covid-19 now that we didn’t know then.

The virus can become airborne

Then: Early advice from the CDC emphasized hand-washing, disinfecting surfaces, and sneezing into your elbow, on the assumption that the coronavirus spread mostly through handshakes, contact with infected surfaces, and through close contact with infectious people (within six feet).

Now: After months of scientific discussion and study, and some confusing communication to the public, the experts agree: The virus can become airborne — within tiny, suspended droplets called aerosols — and infect people beyond six feet, especially in poorly ventilated indoor spaces, where the aerosols are trapped and build up. The World Health Organization, after six months of mounting evidence, finally agreed with scientists on this point. The risk outdoors is lower, the experts still say, but not zero.

What it means: Covid-19’s many ways of spreading vex all but the most stringent efforts to control transmission, particularly indoors. This is why health experts implore people to avoid large crowds, observe physical distancing, wear masks inside and outside, and continue vigilant hand-washing.

For several weeks, the CDC held firm to the notion that the three recognizable symptoms of Covid-19 were fever, cough, and shortness of breath. Yet each week it seemed doctors were recognizing a new Covid-19 symptom.

Face masks are crucial to control the pandemic

Then: In the pandemic’s early months, health officials stressed hand-washing and social distancing, while discouraging masks, for three reasons: There was an extreme shortage of medical-grade masks for health care professionals; the primary means of spread hadn’t been conclusively determined; and U.S. outbreaks existed only in pockets, having not yet spread to all states or locales.

Now: The science of how to slow or stop the pandemic has been settled for months, and it’s safe to say that every health expert now recommends face masks. Beyond face coverings, health experts advise: Prevent large indoor gatherings, especially at nonessential venues like bars; provide much more widespread testing with quicker results, paired with contact tracing; mandate physical distancing for public places that remain open; direct all this in a coordinated fashion from the federal level. “We truly have great knowledge [of] how we can control the virus,” says Yonatan Grad, MD, an assistant professor of immunology and infectious diseases at Harvard T.H. Chan School of Public Health.

What it means: Science has been largely ignored or applied half-heartedly at the federal level and in many states, and unless something changes, experts don’t expect the pandemic to let up.

“This most wealthy country in the world is letting [the virus] run rampant,” Grad says. “It’s baffling to me. Obviously, there are economic and political pressures, and it seems to me those are winning out over concerns about the health of the populace.”

Covid-19 affects the whole body, not just the lungs

Then: For several weeks, the CDC held firm to the notion that the three recognizable symptoms of Covid-19 were fever, cough, and shortness of breath. Yet each week it seemed doctors were recognizing a new Covid-19 symptom.

Now: By February, studies showed that the virus caused body aches, nausea, and diarrhea in some people. Then came news of anosmia, the loss of smell. We learned of Covid toe, possible brain infections causing dizziness and confusion, and a severe reaction by the immune system leading to blood clots, heart attacks, and other organ failures. More recently, scientists say it looks as if blood vessels are being infected. Few if any diseases cause such a wide variety of symptoms. “It’s been unprecedented in many ways,” says Robert Salata, MD, a professor of medicine in epidemiology and international health at Ohio’s Case Western Reserve University. “In terms of the complications we’re seeing, it’s incredible.”

What it means: “Physicians need to think of Covid-19 as a multisystem disease,” says Aakriti Gupta, MD, a resident at Columbia University Irving Medical Center. Gupta and her colleagues published a review of Covid-19’s effects July 20 in the journal Nature Medicine. “There’s a lot of news about clotting, but it’s also important to understand that a substantial proportion of these patients suffer kidney, heart, and brain damage,” she says. By recognizing all this, doctors can improve treatment and develop follow-up plans to see how people are doing well after they’re discharged. “It’s a relatively new virus, and we’re still learning about its long-term effects,” says the review’s lead author, Kartik Sehgal, MD, a fellow at Beth Israel Deaconess Medical Center.

Younger adults and children suffer, too

Then: From the start, Covid-19 was clearly more dangerous for older people, ravaging in particular nursing homes and long-term care facilities, which have accounted for more than 40% of deaths as of early June. An impression developed that younger adults and children were not at risk.

Now: The risk of death in children and teens is low, “but it is not nil,” William Hanage, PhD, an associate professor of epidemiology at Harvard T.H. Chan School of Public Health, says. And the risk rises consistently with age. These are the numbers of known Covid-19 deaths in the United States by age group, through July 15:

<1: 9
1–4: 8
5–14: 14
15–24: 157
25–34: 844
35–44: 2,169
45–54: 6,021
55–64: 14,693
65–74: 25,268
75–84: 32,066
85+: 40,125

Increasingly, doctors are noting more severe outcomes for children, teens, and younger adults. Salata, the Case Western doctor, sees disturbing trends emerging in younger Covid-19 patients at his university hospital. “The most remarkable thing for me is the fact that we are learning of the catastrophic consequences of this viral infection from strokes in younger persons, multisystem inflammatory syndrome in children, cardiac and renal complications, and the long-lasting consequences of symptoms related to a post-Covid syndrome,” Salata tells Elemental.

What it means: “No age group gets out of this without risk,” Hanage says. And now with the perspective of time, it’s becoming clear that some proportion of infections can leave people in any age group with chronic effects, “and they potentially have consequences that we’re only beginning to learn about,” Hanage says. Further, he and other experts say, when the disease builds in younger populations, as it has been doing in dramatic fashion since late May, it then inevitably infects more older people, leading to the rising number of daily deaths we now see.

The virus ignores seasons

Then: Because heat and humidity reduce the virulence of influenza and some other viruses, slowing their spread in summer, there had been speculation that the novel coronavirus might similarly subside, but outbreaks in March in the Southern Hemisphere, when it was warm there, largely dashed those hopes.

Now: If heat and humidity have any seasonal dampening effect on this virus, it’s clearly minor. Rising case numbers across the U.S. Sunbelt in June and July provide “very abundant evidence” that heat “is not going to help the virus go away,” Hanage says.

What it means: There will likely be a huge “reservoir” of infected people heading into fall, so new infections could surge even more rapidly as colder weather forces people into more crowded indoor situations. That surge would coincide with the expected seasonal rise in flu cases, potentially overloading health care systems. “We can expect there to be an even greater challenge as we move into the colder months,” Hanage says.

Science has been largely ignored or applied half-heartedly at the federal level and in many states, and unless something changes, experts don’t expect the pandemic to let up.

Covid-19 is far more deadly than the flu

Then: Back in March, President Donald Trump repeatedly suggested Covid-19 was like the flu, and therefore nothing much to worry about. At the same time, Fauci said the disease was “10 times more lethal than the seasonal flu.”

Now: The Covid-19 death rate remains somewhat elusive, largely because the documented number of infections is a gross undercount. The actual case count nationwide is now thought to be about 10 times higher than the official tally, according to a study published July 21 in JAMA Internal Medicine. That estimate is in line with previous scientific speculation. Meanwhile, Covid-19 deaths are likely undercounted, too. But the death rate is “beginning to come into focus now,” Hanage says. “Very roughly speaking… we would expect roughly one in every 200 infections to lead to death,” he says. The infection fatality rate for flu is about one in 1,000. However, the death rate for Covid-19 varies dramatically by age group, Hanage and other experts are quick to note. “The risk of death starts to tick up somewhere around the age of 50, and it gets extremely high over the age of 70,” Hanage says.

What it means: “Per infection, this virus is about five times as dangerous as flu,” Hanage says. How high is that? “It is plenty high enough to kill a very large number of people when you consider that this is a pandemic virus for which there is not really any immunity in the population and we would expect it to end up infecting a large fraction of the population,” he says. One predictive model that has “performed better than most” so far, according to former CDC Director Tom Frieden, currently projects the U.S. death toll will reach somewhere between 177,000 and 272,000 by November 1. If the disease is not reined in by some means — whether a vaccine or stricter social measures — epidemiologists expect 1 million or more eventual U.S. deaths from the pandemic.

The virus won’t disappear on its own

Then: “We are preparing as if this were the next pandemic,” Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases at the CDC, said in a press briefing on February 3. Two days later, Amesh Adalja, MD, an infectious disease expert at the Center for Health Security at Johns Hopkins University, said, “It appears we are currently in the early stages of a mild pandemic.” Meanwhile, from February 10 through July 1, President Trump predicted at least 19 times that the coronavirus would just go away, including claiming that “like a miracle, it will disappear.”

Now: Muddled messaging all along and lack of a national plan led to patchwork policies that in many states largely ignored science and statistics, leading to a U.S. toll that has exceeded the number of total deaths from influenza or any other infectious disease outbreak in any year or season since the flu pandemic of 1918–19. The United States leads the world in Covid-19 deaths, with 24% of the global total despite having just 4.2% of the world’s population. On July 21, the president changed his tone. “It will probably, unfortunately, get worse before it gets better,” he said, adding: “If you can, use the mask.”

What it means: The lockdowns, which aimed to “flatten the curve” and buy time to develop a coherent mitigation strategy, tools, and supplies, were wasted, at great cost economic cost. The sheer number of infections has now spiraled beyond the point where voluntary mask-wearing and social distancing alone will get the pandemic under control. The death toll is rising again, crossing the 1,000 mark on July 21 for the first time since June 10. Meanwhile, the nation has not invested sufficiently in testing capacity, experts say, and turnaround times are too slow to sufficiently enable useful contact tracing and effective isolation of newly infected people.

People spread the coronavirus unwittingly

Then: On January 21, 2020, when there were 300 known infections in China and one in the United States, health officials were already getting a sense of the looming global threat, a sense that quickly turned to alarm. “It’s very, very transmissible,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Disease, said on February 2. But only with time would they realize why.

Now: “An important thing we have learned is the role of presymptomatic transmission and transmission from people who are only mildly ill,” Natalie Dean, PhD, an epidemiologist and assistant professor of biostatistics at the University of Florida, tells Elemental now. “Clusters of infections can be started by people with no or very mild symptoms.” Meanwhile, the extent to which small children catch, carry, and spread Covid-19 remains unclear, in part because kids have been largely sequestered, and because they’re thought to have milder symptoms in most cases, so their infections may often go unnoticed. Hanage has looked over the studies and offers this estimate: “Younger children are, roughly speaking, about half as likely to become infected in a contact as adults are, maybe a little bit less likely to transmit, but that’s not clear.”

What it means: People who aren’t aware they have Covid-19 but are infectious can cause superspreader events, which infect dozens or even hundreds of people at once. In recent weeks, the spread has been led by younger adults crowding bars and other places where masks have been anathema. Experts think that about 80% of Covid-19 infections are caused by about 20% of infected individuals. If children return to school this fall, the extent to which they exacerbate the viral spread remains to be seen.

A vaccine is almost certain

Then: From the outset of the crisis, there’s been cautious optimism that a vaccine would eventually be developed, but veterans of vaccine creation have been careful to say it often takes years, and there was no guarantee one would ever be developed for Covid-19.

Now: The U.S. government has pledged billions of dollars toward quick development of a vaccine, and several teams around the globe have been working toward the goal for months.

Dozens of vaccine candidates are in various stages of testing by different companies and research groups. Optimism was recently boosted when three separate groups — in China, at Oxford University, and in the United States — announced successful early trials, each generating an immune response to the novel coronavirus and appearing to be safe. These candidate vaccines must go through larger human trials involving people beyond the healthy 18-to-55-year-olds typical of trials so far. And then they would need to be produced in great quantities — hundreds of millions of doses for the United States alone, and billions globally. Scaling up production, after any federal approval, is expected to take months.

What it means: “Absolutely, for sure,” a successful vaccine will be developed for Covid-19, says Barry Bloom, PhD, an immunologist and infectious disease expert at Harvard T.H. Chan School of Public Health. “And we will get more than one.” With each company able to ramp up production of its own vaccine separately, that would mean more total doses would be available sooner. How effective any of the vaccines will be remains to be seen — a vaccine needs to be just 50% effective to make it to market, Bloom says. The other big question is when, says Andrea Amalfitano, DO, dean of the College of Osteopathic Medicine at Michigan State University.

Expecting a vaccine being administered to the public by March 2021 “is not out of the realm of possibility,” Amalfitano says in a phone interview, but he adds that there is still no guarantee of a vaccine that soon.