A month ago, there were about a dozen cases of the novel coronavirus in the United States — all involving people who had traveled overseas. President Trump was assuring Americans that the virus was contained, that there wasn’t much risk posed to the nation. No American had died.

Over the past several weeks, the threat has increased exponentially. In mid-February, the virus was already established in the United States, spreading silently, and the number of cases here soon spiked. In short order, largely because a lack of testing made it hard to draw boundaries around affected areas, it became necessary to broadly restrict people’s movement. Schools and restaurants closed. New rules were implemented to limit the extent to which Americans interacted with one another, with an eye toward tamping down the number of cases of the virus and, therefore, the number of deaths that would result.

Yet, oddly, the belief that the virus poses a threat hasn’t increased since early February. Polling conducted by Marist University for NPR and “PBS NewsHour” shows that although concern about the virus has increased since February, the number of respondents saying the virus poses a real threat has plunged.

It’s fair to note that the “threat” question forced a choice between “real threat” and “blown out of proportion,” meaning that some respondents who consider it a threat might have thought “blown out of proportion” was a better fit. But what’s important here is who’s driving both of those shifts: Republicans.

Since February, about the same percentage of Republicans have expressed concern about the virus, while concern among Democrats and independents has surged. Democrats are slightly more likely to consider the virus a real threat, while Republicans are much less likely to do so.

In the abstract, this can be waved away as another example of the country’s deep partisan divide. In a practical sense, though, dismissing the virus is deeply dangerous. A willingness to assume that it doesn’t actually pose a threat almost certainly correlates with a disinterest in taking precautions against it — and, therefore, puts you and those around you at increased risk.

Polling from the Kaiser Family Foundation released Tuesday shows that Republicans are, in fact, consistently less likely to take the sorts of precautions that will lower their risk from the virus. About 8 in 10 Democrats took at least one of the precautions about which the poll asked; only about half of Republicans did.

The NPR-“PBS NewsHour”-Marist poll found a similar divide. Republicans were less likely to say that they’d eat at home more often instead of going out (60 percent of Democrats vs. 36 percent of Republicans) or that they were canceling plans to avoid crowds (59 percent vs. 40 percent).

Why have Republicans become increasingly skeptical about the virus? In part, certainly, it’s a function of what they’re hearing from sources they trust. Republicans broadly trust the coronavirus information they hear from Trump, with nearly three-quarters expressing that they have at least a good amount of trust in Trump’s info. By contrast, less than half have that level of trust in the news media.

This is why it’s so important that both Trump and media outlets with large Republican audiences — meaning Fox News — convey accurate information about the virus. Trump briefly broke from his habit of diminishing the risk posed by the virus during a news media briefing Monday; that he continue to encourage social distancing measures will be of critical importance moving forward. The Washington Post also reported that Fox’s coverage (which both echoed and probably reinforced Trump’s minimizing the virus) shifted after Trump declared a national emergency on Friday.

Republicans clearly believed Trump and Fox News when they played down the threat posed by the virus and accused the media and Democrats of overstating the threat. Hopefully they believe the new line from Trump and Fox News — and hopefully that line continues.

You probably noticed a middle ground on the chart above: Everyone has a lot of confidence in the opinions of public health professionals. To the extent that the federal government’s messaging about the coronavirus can be driven by the government experts on the pandemic, the more likely it will be that accurate information is conveyed and accepted.

Republicans have had a consistent level of confidence in the federal government during the crisis, according to the Marist polling. They’re alone in that. Overall, confidence in the federal government’s efforts to curtail the spread of the virus have sunk by 15 points, perhaps a natural response to the fact that the number of cases in the United States has spiked. That drop was bigger among Democrats.

What these polls indicate, more than anything, is the dangerous overlap of partisanship and views of the coronavirus. Unlike many political issues, there are objective facts here. The number of cases is rising, the virus is not contained, the risk is real and efforts to limit interactions might keep the number of cases from overwhelming health-care facilities — a problem that would affect anyone needing treatment, not just those with covid-19, the disease caused by the virus.

The virus is here. To ensure that its effects are as minimal as possible, Americans need to understand the threat it poses soon — meaning immediately. If partisanship affects that understanding, partisan actors like the president need to maintain a message focused on the threat, or they need to defer to the health experts who might get that message out.

That attitudes toward the coronavirus have shifted so dramatically away from concern over the past month is a stunning indictment of efforts to link the virus to politics, including by Trump.