10 Surprising Things We've Learned About the Coronavirus

3. People with no symptoms can spread it.

Normally, we can slow the spread of a virus by isolating people as soon as they show symptoms. But that doesn't work for the coronavirus because infected people can spread it even if they have no symptoms. Researchers say that was one of most unexpected, and frightening, things they've learned about the coronavirus.

"We completely missed the boat on that,” says Cameron Wolfe, an infectious disease specialist and cochair of the clinical COVID-19 task force at Duke University Medical School. “Young people can acquire COVID, shed it highly, but be completely oblivious. Yet the 75-year-old they walk past is going to be infected and get very sick.”

A study published Jan. 7, 2021, in JAMA Network Open estimated that about 59 percent of all transmission is caused by people who haven't yet developed symptoms or asymptomatic people who never develop symptoms. That's why precautions like screening questions and temperature checks aren't enough to prevent its spread.

4. COVID-19 is more than a respiratory disease.

Doctors originally thought COVID-19 was a disease that caused a respiratory tract infection, perhaps with complications.

But they soon realized that the virus was also causing damage in the kidneys, liver, cardiovascular system and even the brain. And then there was its most distinctive symptom: the loss of sense of taste and smell. “The clinical spectrum [of symptoms] continues to catch us by surprise,” Wolfe says.

Many experts now believe the virus is likely a vascular disease, not a respiratory one. If the virus infects blood vessels and circulates through the body, that may explain its ability to cause so many wide-ranging symptoms. It could also explain why high blood pressure alone puts people at significantly higher risk — another unusual characteristic of COVID-19.

5. It can cause your body to attack itself.

Doctors say the part of the disease that has emerged as most perplexing is how it causes an exaggerated and dangerous inflammatory response in some people. That response, caused by a patient's own immune system, can lead to severe complications such as multi-organ failure or septic shock. “There's not really another virus that does that to the same extent,” Wolfe says.

The inflammatory aspect of the disease prompted doctors to adjust their treatment of COVID-19 patients, Wolfe says. Rather than using medicines that attack the virus, they have found that immunosuppressive drugs typically used for inflammatory diseases like rheumatoid arthritis can help COVID-19 patients during later stages of the disease.

6. It's mutating.

While many Americans may have been surprised to learn that the coronavirus is mutating, scientists say that's expected when it comes to viruses. What was more interesting to them was the rate at which new variants emerged — and fortunately, it hasn't been as bad as it could be, Vermund says. Both HIV and seasonal influenza mutate more frequently, he says.

As of early March, the CDC was tracking at least five coronavirus variants believed to be more contagious than the original strain.

"It's probably good news that it isn't 50,” Vermund says. At the current rate, vaccine manufacturers should be able to keep up and develop vaccines that protect against more than one strain, he says.

7. The older you are, the more dangerous it is.

Age is by far the strongest predictor of your risk from COVID-19, and that risk “increases steadily as you age,” the CDC says. About 95 percent of COVID-19 deaths in the U.S. have occurred among people who were 50 or older, and 8 out of 10 have been of people 65 and older, according to the CDC.

"Age being such a big factor was a surprise,” Vermund says, noting that there aren't many other diseases in which age alone plays such a critical role.

Fortunately, studies show avoiding chronic conditions such as obesity, high blood pressure and diabetes can significantly improve your odds, no matter what your age.

8. People of color are at higher risk.

African Americans, Latinos and Indigenous people have had the highest rates of death from COVID-19 in the U.S., with all three groups dying from the virus at around twice the rate of their white counterparts, according to the CDC.

Experts believe a variety of factors contribute to the disparity, including unequal access to medical care and health insurance, economic and cultural factors, and how much exposure to the virus a person may have on the job.

9. The vaccines work.

Vermund called the COVID-19 vaccines that are rolling out now “some of the best vaccines ever developed in the history of time.” All three — from Moderna, Pfizer-BioNTech and Johnson & Johnson — are at least 86 percent effective against severe disease, and in their clinical trials, not one person died from COVID-19 after getting the shot. “You can't do much better than 100 percent protection from death,” Vermund says.

The speedy development of COVID-19 vaccines was the result of hard work and collaboration from scientists from across the globe, but there was also a little bit of luck involved, Vermund says.

"The virus was very friendly to us in presenting a spike protein that was easy to replicate biotechnically and [that] stimulates a protective immune response,” he says, noting that other viruses haven't always presented such an easy path to vaccine development.

10. It's not going away.

Most experts now believe the coronavirus will never totally be eradicated. Even if the required 70 to 85 percent of the U.S. population gets vaccinated for herd immunity, the virus has already spread too far, and it's changing too fast.

The goal, instead, is to vaccinate enough people worldwide that COVID-19 becomes a relatively minor illness for most people, like the seasonal flu, Wolfe says.

Occasionally, there may be a severe case in someone who didn't get vaccinated or who didn't have a strong immune response to the vaccine. But, Wolfe says, the hope is that in two to three years, “the vast majority will be protected and going about their lives normally.”

Michelle Crouch is a contributing writer who has covered health and personal finance for some of the nation's top consumer publications. Her work has appeared in Reader's Digest, Real Simple, Prevention, The Washington Post and The New York Times.