Was it really only four months ago that we heard a new coronavirus was only a threat to one province in China? Only two months ago that it seemed like healthy people didn’t need to worry about COVID-19?
We’ve had a real-life repeat of the lesson our high-school science teachers tried to pass on: knowledge is constantly evolving, and some of what we think we know now will eventually be proven wrong. Now it’s just happening faster than most of us are accustomed to, and sometimes faster than we can keep up with.
Below, we’ve compiled some of what we’ve learned in the past few months about the new virus, the disease it causes and how it might affect you. We’ve also included some questions that are still unanswered. Keep in mind, all of this could change as scientists continue to learn more and health officials refine their guidelines for how to respond to the pandemic.
What we know now
It infects an unusual combination of sites, making it easier to spread and more deadly: The virus that causes COVID-19 is being found both in the upper airway (nose and throat) and deep in the lungs, said Dr. Vineet Menachery, an assistant professor in the department of microbiology and immunology at the University of Texas Medical Branch at Galveston. That’s a bad combination, because it means the virus spreads relatively easily, but also can cause severe pneumonia.
It’s relatively rare for a virus to do both, which makes the new coronavirus virus a challenge to contain and treat.
Viruses that infect the nose and throat, like those that cause the common cold, spread easily when people cough or sneeze, but rarely cause more than discomfort, Menachery said. Other viruses, like those that cause Severe Acute Respiratory Syndrome and Middle East Respiratory Syndrome, get deep into the lungs and kill a significant percentage of people who are infected, but don’t spread easily, he said.
The virus can kill multiple ways: Some people have died after debris built up in the air sacs in their lungs, while others had an immune overreaction that damaged the lungs or other organs. In some cases, the virus appears to have attacked the kidneys or the heart.
One poorly understood way the virus kills is through blood clots, which can cause a stroke or heart attack, or cut off blood flow to limbs, requiring amputation in extreme cases.
Dr. Barbara Melendez, a vascular surgeon at Vascular Institute of the Rockies, said she’s seen more cases of thrombosis — a clot causing a problem with an organ or limb — than usual, and in people without risk factors like heart disease. Depending on where a clot lands, it can cause chest pain, shortness of breath, swelling in the legs or other symptoms, she said.
“Everybody has seen an increase in their thrombosis complications,” she said. “We’ve seen them in the legs. We’ve seen them in the lungs.”
There have been few deaths in children, though some pediatricians are raising alarms about kids developing organ damage because of an immune overreaction to COVID-19 infection. Fortunately, that remains rare.
The symptoms are more varied than previously believed: Initially, descriptions of the virus’ symptoms focused on coughing, fever and shortness of breath. Some people may experience those as well as other symptoms, or may not get the classic symptoms at all, according to the Centers for Disease Control and Prevention. Other possible symptoms are chills (which often co-exist with a fever), headaches, muscle aches, a sore throat and losing your sense of taste or smell.
Other possible symptoms are confusion and gastrointestinal problems like nausea and diarrhea, though those are most common in elderly people. Some people are developing skin rashes or inflammation in their toes, which so far is associated with a less severe disease course.
Malaria drugs aren’t the solution: Despite the hype around hydroxychloroquine, a drug used for malaria and some autoimmune diseases, it didn’t pan out. A study by the Veterans Administration found those given the drug were more likely to die than those who received standard supportive care, possibly because the drug can have serious side effects, including damage to the heart.
What we still don’t know
How the majority of people get infected: It’s clear the virus can spread through droplets when people cough or sneeze, and that a person who touches those droplets and then touches their face can get infected. What’s less clear is whether the virus can spread through the air when a person talks or breathes nearby, and how far it can go. It appears that people can transmit the virus before they develop symptoms, but researchers aren’t sure how common that is, or when most infected people become contagious.
How deadly the virus is: Calculating the fatality rate of a virus is pretty simple, in theory: you divide the number of people who die by the number infected. The problem is that we aren’t really sure of either number.
The number of infections is being undercounted because many people have only mild symptoms, or no symptoms, and don’t get tested. But the number of deaths is also undercounted, because some people have died of COVID-like symptoms without being tested, and the first deaths may have come weeks before the United States was even looking for the virus.
Some analyses have found far more people died in March and April than would be expected under normal conditions, with far more “excess deaths” than recorded coronavirus deaths. It doesn’t prove that all of those deaths were caused by the virus, though it’s notable that areas with large epidemics also had more unexplained excess deaths.
Why some people get so much sicker than others: It’s not unexpected for a virus to hit older people and those with chronic conditions harder than the young and healthy, but there are still unanswered questions about why some people become seriously ill and other don’t.
For example, men are more likely to be hospitalized from the new virus or to die from it. One theory is that the difference is about behavior, such as men having higher smoking rates or waiting longer to seek care. An alternate theory is having two X chromosomes gives women a stronger immune system, or that female sex hormones may be protective.
Whether people who’ve been infected have immunity: There are several tests that can tell you if you have antibodies, meaning your immune system has responded to this virus before. What we don’t know is whether having antibodies means you’re immune, or how long that immunity might last. That makes it difficult to figure out when it’s safe for people to go back to work. Tests also vary widely in quality, so you can’t take a positive, or negative, result as Gospel.
How bad things could get: Different models have projected anywhere from 60,000 to 2 million deaths in the United States. The country already has passed 60,000 coronavirus-related deaths, so unfortunately the lowest projections are out. Much will depend on decisions made over the next few months. Relaxing social distancing rules is expected to bring in an increase in cases. The question is what a balance might look like, where more people can work and socialize without overwhelming the public health system’s ability to test, trace and isolate those who could be infected.