Recent data suggests patients may have been infected with the new coronavirus in the United States earlier than public health officials originally thought—and that has prompted many Americans to wonder if they've already been infected with the virus. But experts are skeptical.

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Why so many people think they've already had Covid-19

Public health officials in recent weeks have reported data suggesting that there were patients infected with the new coronavirus in the United States earlier than they had previously thought. For example, data from autopsies performed on deceased patients in California show one patient who was infected with the virus died on Feb. 6, which is weeks earlier than a death that occurred on Feb. 29 that was reported as the first death in the country linked to the new coronavirus.

In addition, researchers in New York have suggested that data indicate the virus started spreading in the state as early as mid-February, weeks before the first case of Covid-19 was reported in the state.

The reports have prompted many Americans to wonder whether respiratory illnesses they had in late-2019 or early-2020 may have been undiagnosed Covid-19.

For example, Brian Gustafson, a coroner in Illinois who also is a nurse, said he was unable to perform tests for the new coronavirus post-mortem and, as a result, he believes that deaths and illnesses related to the virus were missed in his county during the early weeks of this year. "I think it was here long before we knew it," he said.

Gustafson also believes that he contracted the new coronavirus in January from a deceased patient who was infected.

Jeffrey Smith, a Santa Clara County executive in California and a doctor, said his wife—who also is a doctor—told him she was perplexed by some patients she had seen in December. "I remember her telling me back in December of a number of patients who came in with flulike symptoms who were testing negative for the flu," Smith said. "I just wonder if those were patients that had [Covid-19]."

What the experts say

Experts estimate that the United States' true Covid-19 case count is much higher than reported figures suggest, as persistent lags in testing have left many Americans with Covid-19 symptoms unable to  access tests to confirm the infection. In addition, some people may experience extremely mild or asymptomatic cases of Covid-19 and therefore could be unaware they are infected with the new coronavirus.

However, experts say it's also likely that some people were sickened with other diseases and merely are projecting their desire to have already recovered from Covid-19 onto those previous illnesses.

For instance, JoAnna Fischer, told the Washington Post that she's certain she had Covid-19 when she was living in Pennsylvania in September 2019 because she had lost her sense of smell, had a cough and chest pain, and had to be treated with supplemental oxygen for three months. Fischer said her husband and her cat experienced similar symptoms.

However, Trevor Bedford, a computational biologist at Fred Hutchinson Cancer Research Center who has been tracking the new coronavirus' spread, has said, "There is 0.0% probability that [the new coronavirus] was circulating with community transmission in the U.S. in or before [November] 2019."

Bedford has done genomic analyses of the new coronavirus, and his research suggests the first-known case of Covid-19 in the United States occurred in mid-January in Washington state, meaning it's highly unlikely the disease caused any respiratory illnesses in late-2019 or early-2020, Mashable reports.

Nicholas Reich, an associate professor of biostatistics at the University of Massachusetts, has compared reported rates of influenza-like illnesses with rates of negative flu tests in December 2019 and January of this year. Reich sought to test the theory that if reported rates of influenza-like illnesses increased alongside rates of negative flu tests, it could mean another pathogen was circulating. However, Reich's analysis found that, by late-February, those trends were in line with historical norms, according to Mashable.

Reich's lab also looked at such patterns in March of this year and found some deviations from historical norms, though the researchers said it was hard to draw any meaningful conclusions from that data, as it's possible that more people sought care for respiratory illnesses when they typically wouldn't have because of increased awareness of Covid-19.

Ultimately, Reich said he thinks it's unlikely the new coronavirus was circulating in America before late-February or early-March. "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," he said. "Data points like (what's happening in Italy) make it clearer to me just how this is really different from seasonal flu."

Ruth Collins, an associate professor of molecular medicine at Cornell University, said it's likely a different virus was circulating this past winter that caused symptoms similar to those associated with Covid-19.

But the desire to have already had and recovered from Covid-19 is human nature, as people tend to naturally anticipate positive outcomes, according to Tali Sharot, a professor of cognitive neuroscience at the University College London. "When there is something we want to believe, we are very good at interpreting the evidence in a way that would support that belief," she said.

"Everyone desperately wants to be immune to this thing," Andrew Noymer, an associate professor of public health at the University of California-Irvine, said, "and they're projecting their hope onto the data" (Judkis, Washington Post, 5/6; Ruiz, Mashable, 4/8; Bosman et. al., New York Times, 4/23).