Do You Wonder If You’ve Already Had COVID-19?

Many people had a cold or the flu sometime over the winter. When you look back, perhaps you’ve reflected on your own illness. And you may have wondered: Was that Covid-19?

In our family, we’ve certainly wondered if we’ve already had Covid-19. Just as coronavirus was starting to spread in the Pacific Northwest, we had a cold run through our household. All of us had a cold for a few days, and we’ve talked about whether that was actually Covid-19. We know that most people have mild cases of Covid-19 and many show no symptoms. Covid-19 often presents as an illness similar to a cold or the flu. We also know that the coronavirus was spreading in our community at the time. Seattle was an early hotspot. And the coronavirus showed up in testing where we live right when we had a cold. So did we already have Covid-19?

Have you found yourself wondering the same thing? How do you decide if you've already had it?

Here is the approach that people will typically take, and it relates to how about how people make decisions when they have incomplete information. And if you were sick, but didn’t have a test, then you have incomplete information.

First, we may consider Covid-19 symptoms. Have you looked at the growing and varying list of symptoms? The symptoms vary based on how severe each person’s case is. But maybe you experienced some of those symptoms. A cough, shortness of breath, fever, chills, muscle soreness, a sore throat, loss of taste and smell, persistent difficulty breathing, and problems staying awake. Have you had any of those in the last few months? If you answer yes to any of these, then you may start to wonder what you actually had. This is one of the risks of consulting Dr. Google. You look at symptoms and worry that you have that disease. We do this because we can check some of the symptoms. And with Covid-19, we know that not everyone has all of the symptoms. So we start to wonder, maybe, maybe it was Covid19.

Second, we start thinking about possible exposure. Do we know anyone with the coronavirus? Have you somewhere where someone with Covid-19 was? In my case, the answer to both these questions is yes. We have friends who have had Covid-19, and some are still fighting hard. In my work at my university, we were explicitly told to assume that most spaces on campus had exposure to the coronavirus.

And then we start really thinking that we’ve had Covid-19. I don’t know about you, but if I had a mild case two months ago, that would be fine. It would mean I had a mild case and that now I might be immune. I’d actually prefer that. I could stop worrying about catching and spreading Covid-19.

But here’s the problem. I am experiencing the effects of a confirmation bias. A confirmation bias is a very common cognitive bias. A typical form of thinking that can lead us to incorrect answers. When we fall for a confirmation bias, we start with an idea. In this case, the idea is that maybe I have already had Covid-19. We then search for information that is consistent with that idea. We look for confirmation. We see symptoms we may have experienced. We think about possible exposures to the virus. We see and remember everything that is consistent with this idea. We can quickly confirm the idea we started with.

When we experience a confirmation bias, we not only see confirming information, but we also ignore anything that is inconsistent with the idea. So what information are we ignoring when we confirm the idea that we’ve had Covid-19 already? We ignore all the symptoms that we didn’t experience. I may have had some of those symptoms, but definitely not all. When we consider the symptoms, we also ignore other simpler explanations. In this case, it probably was a cold, or maybe the flu. For me, I have been suffering from my normal spring allergies for the last two months. And that means not only the runny nose but also asthma. So my symptoms are very consistent with other, simpler explanations. But I can ignore those explanations. And instead, I focus on my preferred answer.

We also ignore the disconfirming information about exposure. Yes, the virus was spreading in my community and probably on my campus. But at the time, it had not spread very widely. Our family went into isolation early. We have had limited contact and exposure over the last two months. Even now, with relatively effective social isolation in my community, the virus has had limited spread.

We also ignore important data about the spread of the virus. Whenever I wonder if I had Covid-19, I remind myself of how few people have had the disease so far. The numbers remain low in my community. And medical researchers are just starting to track how many people have been exposed. They do this by conducting serology tests, or antibody tests. These show if someone has the antibodies for the coronavirus, indicating they’ve had it and are now potentially immune.

From the few studies that have been conducted, we know that very few people overall have had the virus, at least based on antibody testing (see stories from the Washington Post and Science). In most studies so far, less than 5% of the population shows evidence of having been exposed in places where the virus has been actively spreading. In New York City, a survey for antibodies showed that around 20% of people had been exposed. So even in the biggest hotspot in the United States, most people (80%) have not been exposed. Based on the numbers, I haven’t had Covid-19. And you probably haven’t either.

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But the effect of a confirmation bias is that we can ignore this disconfirming data. We ignore all the information that says it was just a cold and we are unlikely to have been exposed. Instead, we focus on all the details that are consistent with our beliefs. We search for confirmation. And we often see and remember the confirming information. All of us can become victims of the confirmation bias.

Note: This was written for people wondering about a past sickness. If you are currently experiencing symptoms noted by the CDC, that is very different. You should check with your doctor or community health center. If you have been exposed to the coronavirus, then you should follow CDC recommendations for isolation while waiting to get a test.