Since the novel coronavirus emerged in the United States, more than 12.5 million Americans have been confirmed to have been infected by it. The actual number is unquestionably far higher than that, given the slow rollout of effective testing for the virus. But even by itself, that number constitutes nearly 4 percent of the population.

In the Senate, the rate of infections is even higher. As of writing, eight senators have tested positive for the virus, according to data compiled by GovTrack. That’s an 8 percent rate of positive tests, more than twice the national measure.

All eight of those positive tests, though, occurred among members of the Republican caucus, which currently numbers 53 senators. In other words, nearly 1 in 6 Republican senators has contracted the virus — about 15 percent of the caucus.

Republicans in the Senate have been about four times as likely as Americans overall to have tested positive for the virus.

It’s likely that at least two other senators, both Democrats, contracted the virus in March when testing was more limited. Sens. Robert P. Casey Jr. (Pa.) and Tim Kaine (Va.) both reported symptoms similar to those caused by covid-19, the disease caused by the virus, and later tested positive for antibodies, suggesting a previous infection.

If they did contract the virus, the infection rate in the Senate rises to 10 percent overall.

One estimate of the number of infections nationally, including both confirmed and unconfirmed infections, has the total at more than 49 million. If that’s accurate, Senate Republicans have been only slightly more likely than Americans overall to have contracted the virus.

The first senator to confirm a positive test result was Sen. Rand Paul (R-Ky.). His result came in late March. It wasn’t until five months later that the next senator, Bill Cassidy (R-La.), tested positive. In both cases, the senators’ tests came while rates in their states were low or declining.

Then cases came in a flurry. Three senators tested positive at the beginning of October: Mike Lee (R-Utah), Thom Tillis (R-N.C.) and Ron Johnson (R-Wis.). Lee and Tillis attended ceremonies at the White House focused on the nomination of Amy Coney Barrett to the Supreme Court.

Over the past 10 days, three other senators — Rick Scott (R-Fla.), Charles E. Grassley (R-Iowa) and Kelly Loeffler (R-Ga.) — tested positive, as well. Their infections were confirmed as each of their states is seeing a surge in new cases. Of course, most states are at this point.

As The Washington Post reported last week, the Senate, which is controlled by Republicans, has different and less stringent rules for containing the virus than does the Democratic-led House.

Last week, Sen. Ted Cruz (R-Tex.) said that Sen. Sherrod Brown’s (D-Ohio) request that Sen. Dan Sullivan (R-Alaska) wear a mask was “idiotic” and “an ostentatious sign of fake virtue.” At the time, Sullivan was presiding over the Senate proceedings, sitting just feet from Senate staffers.

Two days later, Grassley was confirmed to have contracted the virus. The day before, he had been presiding over the proceedings in much the same way as Sullivan. He, too, wasn’t wearing a mask.