POLL: One-third of Americans say they might have had the coronavirus, but just a fraction have a good reason to think so

• An Insider poll of more than 1,000 Americans found that 33% of respondents think they might have had the coronavirus.
• Of those who said they believed they had it, just 4.6% said they had been tested and diagnosed with COVID-19.
• Some evidence suggests the coronavirus may have been spreading in the US by late December, but most people who fell ill earlier in the winter probably had a different virus.

A third of Americans think they might have had the coronavirus, Insider found in a poll of 1,099 people.

More than 33% of respondents thought they had "definitely," "probably," or "maybe" had the virus. But only 4.6% of respondents — just 17 people — said they were actually tested and diagnosed with COVID-19.

Among those who thought they could have had the coronavirus, more than half cited cold or flu-related symptoms earlier in the year as the reason. About 20% said they were seriously ill with coronavirus symptoms but were unable to get tested.

"In the winter, there are a lot of different viruses that circulate in US populations," Lauren Ancel Meyers, an epidemiologist at the University of Texas at Austin, told Business Insider. "So if someone has flu-like symptoms or coronavirus-like symptoms, there's many different viruses that could have potentially caused them."

Of all the respondents, 11% said they lived in a place that was severely affected by the coronavirus. Roughly 3% said they were confident that they "definitely" had contracted the virus. That aligns with expert estimates and antibody-testing studies which suggest that 5% or less of the US population has been infected.

Some people may have had coronavirus in late December

A few survey respondents said they had symptoms as early as December 2019. One respondent said that they were "seriously sick for the entire month," adding that they "worked at a place that was a hotbed for tourists and travelers."

Some evidence does suggest that the virus was already spreading in the US and Europe by late December.

"I think that's highly plausible," Meyers said. "Well back into December, there was a period of time where there was a lot of international travel in and out of Wuhan."

In Florida, at least 170 confirmed COVID-19 patients first reported symptoms from December 31 to February 29, according to the Miami Herald. In Washington state, two people fell ill in December and later tested positive for COVID-19 antibodies, The Seattle Times reported. In France, a man arrived at a hospital outside Paris coughing up blood on December 27. His sample later tested positive for the coronavirus.

California is also trying to identify its earlier coronavirus patients. On April 23, Gov. Gavin Newsom asked coroners and medical examiners to review the state's deaths as far back as December. The decision came after new autopsy results showed that COVID-19 killed two people in Santa Clara County on February 6 and 17, weeks earlier than the deaths previously considered the state's earliest.

Still, Meyers said, most people who thought they had coronavirus in winter — even as late as January or early February — are probably mistaken.

"Given that there were so many viruses that were probably spreading at the time, it's probably pretty unlikely," she said.

SurveyMonkey Audience polls from a national sample balanced by census data of age and gender. Respondents are incentivized to complete surveys through charitable contributions. Generally speaking, digital polling tends to skew toward people with access to the internet. SurveyMonkey Audience doesn't try to weigh its sample based on race or income. A total of 1,109 respondents were collected April 28-29, 2020, a margin of error plus or minus 3 percentage points with a 95% confidence level.