Initially, when news of novel coronavirus came out of China, experts defined it as fever and shortness of breath, among other symptoms. By making that their case definition, they only went after symptomatic people, says Dr. Jeremy Cauwels, senior vice president of quality for Sanford Health, a healthcare system covering the upper Midwest.
“Out of 100 symptomatic people, you would see about 20 people that would need to be in the hospital, and about five people who would need to be in the intensive care unit,” Cauwels says. “As we are now understanding, fever doesn't have to be part of the disease every time. As we test more people, we're seeing a far larger reservoir of people who have minimal symptoms or no symptoms.”
The result is this group of people is making the actual number of people who are sick, need to be hospitalized or need to be in the intensive care unit because of this disease, a far lower percentage than experts initially thought.
“And the other part that's interesting, at least in the Midwest, is that even of the people who are symptomatic, we're still finding lower numbers of hospitalizations and lower numbers of intensive care unit or critical illness compared to what we were initially estimating,” Cauwels says.
When COVID-19 first struck the U.S., epidemiologists didn’t know the attack rate, or how many people would get the virus. Experts are starting to get a sense of what the attack rate might be. Cauwels says he’s seen as low as 20% of a population affected during an outbreak. And on the high end, he’s seen up to 58% affected.
“Now in those situations, there's lots of gray area in the middle. But a vast majority of those patients are actually asymptomatic,” he says.
Do antibodies equal protection?
“Antibodies equal exposure for sure. Whether antibodies equal protection is really the question all of us have right now,” Cauwels says. “We think it does. It does in many other illnesses.”
For example, he says once you get the chickenpox and you have antibodies to the chickenpox, you're probably never going to get chickenpox again. However, if you've had influenza one year, you can still get influenza the next year. If you were checked, you would show antibodies for it.
“Now the question is whether this Coronavirus is going to behave more like influenza or more like chickenpox,” Cauwels says. “Will what your body learned about it the first time be enough to keep you from getting it or at least getting it less severely the second time?”
Unfortunately, there are only two ways to know. One way is to have a big population that you keep an eye on over the course of a couple of years to see if they get COVID again. The second way is to actually expose people to COVID-19 again after they have antibodies.
“Considering the danger that is severe COVID disease, I'm not sure anybody is willing to go to that step right now and I wouldn't until we get better at the treatment,” he says.
Tim Loula, DVM with Swine Vet Center, believes understanding how coronavirus antibodies work in swine could offer human doctors insight as they battle COVID-19. Coronavirus antibodies in pigs have been strong/protective enough to eradicate porcine epidemic diarrhea virus (PEDV), a novel coronavirus that upset the swine industry in 2013 and 2014, from sow herds. Read more here: Antibody Testing: A Critical Piece of the Puzzle (for People and Pigs)
“Based on this antibody production in the pig population and the most frequently observed protection those antibodies provide, it’s critical to use these new antibody tests to help provide the science needed to get critical businesses to reopen quickly and remain open safely,” says Dave Bomgaars, DVM with RC Family Farms.