With some people fearful that the pandemic could lead to civil unrest, gun sales have been skyrocketing. In the past, fear of gun-buying restrictions has been the main driver of spikes in gun sales, far surpassing the effects of mass shootings and terrorist attacks alone.

Sales rose sharply in December 2015 after Mr. Obama sought to make it harder to buy assault weapons after the terrorist attack in San Bernardino, Calif. And in January 2013, the heaviest sales came after a call for new restrictions in the wake of the Sandy Hook shooting.

But last month was different. As they prepare for an uncertain future, Americans have been crowding grocery stores to stock up on household essentials like canned beans and toilet paper. A similar worry appears to be driving gun sales.

“People are nervous that there’s a certain amount of civil disorder that might come if huge numbers of people are sick and a huge number of institutions are not operating normally,” said Timothy Lytton, a law professor at Georgia State University and an expert on the gun industry. “They may have an anxiety about protecting themselves if the organs of state are starting to erode.”

Several recent gun-related incidents have been linked to fears surrounding the pandemic. Last week, police in Alpharetta, Ga., arrested a man they accused of pointing a gun at two women wearing medical masks and gloves because he feared he might contract the virus. A man in New Mexico was charged with the accidental shooting death of his 13-year-old cousin with a gun he told police he was carrying “for protection” amid the outbreak. And in Maine, a man with a felony conviction who claimed he needed guns to protect himself during the outbreak was charged with illegally possessing a firearm.

The monthly sales figures are estimates based on the number of background checks reported by the F.B.I., which has been publishing the data since 1998. Many sales, especially in states where background checks are not mandated by law, may have gone uncounted.

In recent weeks, lines have been snaking out of gun stores throughout the country. In many states, estimated sales doubled in March compared with February. In Utah, they nearly tripled. And in Michigan, which has become a hot spot for virus cases, sales more than tripled.

The run on firearms has raised public health concerns and prompted local officials to debate whether gun stores should be temporarily closed. Advocates for stricter safety measures argue that the surge in purchases could pose a safety threat if buyers aren’t trained properly, new guns aren’t stored safely and background checks aren’t completed.

But after lobbying from the firearm industry, the Trump administration said this week that the stores qualified as essential businesses and should stay open during the lockdown alongside pharmacies, gas stations and grocery stores.