In the age of the coronavirus, when nothing is certain and we must plot our every move with the utmost caution, some people are wondering if they need not worry quite as much. What if, they ask, I already had COVID-19 weeks ago but didn't realize or couldn't confirm it?

The search terms "did I have coronavirus" spiked in Google Trends early last month, when it became clear the United States was on the cusp of major outbreaks. People also Googled "did I have coronavirus in January" and "did I have coronavirus in February."

Soccer star Carli Lloyd wondered as much on Twitter in late March, detailing symptoms similar to those caused by COVID-19, including a fever, cough, and shortness of breath.

"Beginning to think my husband and I had the Coronavirus back in mid February," she wrote. "A sickness we have never felt before."

Her replies were full of people wondering about the same scenario in their lives.

It's a simultaneously compelling, legitimate thing to ask and a kind of fantasy that we might indulge in because the alternative — constantly worrying about contracting a highly infectious, potentially fatal disease — is exhausting. The anxiety of extreme social distancing and panic buying might be more tolerable if people knew they'd already survived asymptomatic, mild, or moderate cases of COVID-19.

Unfortunately, the answer to this question is elusive, which means, as far as we know, the risk of contracting COVID-19 remains high. This is particularly true because people who are asymptomatic can infect others, undermining a key assumption about how viruses are transmitted.

There are now more than 370,000 known cases and 12,000 fatalities in the U.S., and public health authorities stress that the only way to stem infections and prevent more deaths is to continue practicing social distancing, hand washing, and other preventive measures.

In order to know how many people in the U.S. have been infected with COVID-19, we'd need widespread availability of highly accurate tests that detect the presence of antibodies against the disease. We also need more scientific information about how long immunity to the disease lasts once someone acquires it. Immunity to common colds, which are caused by coronaviruses, is temporary. Even if someone accurately suspected they'd come down with COVID-19 earlier this year, it doesn't necessarily mean they'd continue to be immune to the virus in the coming months or years.

Then there's the question of whether the timeline makes sense. Prior to the known outbreaks, could people have developed mild or moderate cases of COVID-19 without a simultaneous uptick in severe cases that would've required hospitalization?

Nicholas Reich, an associate professor of biostatistics at the University of Massachusetts in Amherst whose lab focuses on understanding and modeling infectious disease, has been looking for evidence of this happening, and so far sees little data to support that possibility.

For the last two months, and I have been leading a weekly analysis of publicly available influenza-like illness (ILI) data and flu test results from the and state health departments. https://t.co/KrqgiKoyxE

1/ — Nicholas G. Reich () March 27, 2020

He and his lab members noticed influenza-like illnesses increase in December and January and thought perhaps coronavirus had been silently circulating for months. They decided to look at the rate of influenza-like illnesses alongside the rate of negative flu tests as a potential signal of community spread of COVID-19; if illnesses rose but more flu tests came back negative, it could suggest another pathogen playing an unexpected role. By late February, the lab's analysis showed trends that were consistent with historical norms.

Since then, when the lab looked at patterns in March, they saw deviations from the historical norms but it was difficult to draw strong conclusions from that data.

More people went to the doctor with respiratory illnesses and also tested negative for the flu, but Reich said that could be the result of people changing their behavior as media coverage of coronavirus ramped up. In other words, more people sought medical attention for various symptoms because of alarming headlines about COVID-19 but may not have had the disease. The researchers couldn't rule out COVID-19 spreading earlier than thought, but the data also suggested that if the coronavirus had been present, it would've been relatively limited.

Reich believes it's plausible that someone in the vicinity of a hot spot like Seattle or New York could've developed COVID-19 in mid-February, as the disease began to spread throughout communities. (In fact, after this story was published, new research emerged suggesting that the coronavirus began spreading in New York in mid-February.)

"Outbreaks like this take time to build up steam and really start to burn," Reich said.

Still, given the severity of COVID-19, Reich believes it's unlikely that coronavirus was widespread prior to late February and early March. That would've been accompanied by what we're seeing now, and saw in Italy: a fraction of patients streaming into emergency rooms with respiratory distress.

"Outbreaks like this take time to build up steam and really start to burn."

"Based on everything that’s been coming out, I’ve been increasingly feeling as though it would’ve been really hard to miss a large outbreak," said Reich. "Data points like [what's happening in Italy] make it clearer to me just how this is really different from seasonal flu."

Reich also points to genomic analyses of the coronavirus conducted by Trevor Bedford , a computational biologist at the Fred Hutchinson Cancer Research Center in Seattle, which suggest that the first known COVID-19 case in the U.S. occurred in mid-January, in Washington state. That research looked at minor mutations in the virus' genome to analyze when it might have emerged in the U.S. If that analysis is accurate, it would make it far less likely that the disease caused mysterious respiratory illnesses in late 2019 or early 2020.

Ruth Collins, an associate professor of molecular medicine at Cornell University, said it's very likely that a different, nasty virus could've been circulating this winter. Since the symptoms caused by coronaviruses overlap significantly, it would make sense that some people experienced an awful illness that wasn't actually caused by COVID-19 but still produced similar symptoms like coughing, fever, and aches and pains.

Collins said that wondering about whether an illness experienced prior to the coronavirus outbreak was in fact COVID-19 is a form of highly relatable wishful thinking.

"It's part of human psychology," she said. "We always want to think we’re better than we are, that we got lucky, that we escaped it somehow."

It doesn't help, either, that tests to diagnose COVID-19 have been difficult to get.

In the absence of diagnostic testing, we need widespread individual and epidemiological testing to determine who contracted COVID-19 and developed antibodies to the disease. That requires highly accurate serology tests, or blood-based tests, that detect the presence of antibodies against COVID-19. Such testing is being rolled out by the Centers for Disease Control and Prevention, but the government agency is focusing on areas that became hot spots. Antibody tests are not widely available, and though there are efforts to make them accessible to the public, it's not clear when they will be.

Collins also said that antibody tests, like any other test, can be unreliable, producing both false negatives and false positives. Tests, for example, might not pick up antibodies present in small amounts because immunity declined, even if the person was infected.

What we need is more conclusive medical and scientific research on how COVID-19 is transmitted, particularly through asymptomatic people, and a more precise tally of how many people have been infected. Individual access to accurate antibody tests will be important to answering the lingering question about potential infection, but it's still unclear how long immunity lasts.

In the meantime, suspicion of a COVID-19 infection without confirmation is no reason to relax social distancing or hygiene practices.

"This thing is not going to go away fast," said Collins. "We’ve got to know more about how the disease spreads. The idea of testing will give some level of confidence, but it won’t be enough until we know more about how the disease is transmitted."

UPDATE: April 9, 2020, 8:48 a.m. PDT This story was updated to include information about new genomic research suggesting that COVID-19 was beginning to spread in New York in mid-February.

Source: Mashable

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