Adding to the nation’s long list of worries sparked by the novel coronavirus pandemic, the shortage of toilet paper is real.

Store shelves in many places have been picked clean in recent days of single-ply and double-ply, single and jumbo rolls, the cheap stuff and the luxurious quilted squares, too.

Anything will do in an emergency.

The run on toilet paper has struck many people as peculiar, given that the need for the product is not expected to grow as millions of Americans adjust to working from home, closed schools, canceled events and the other abrupt interruptions to daily life caused by the pandemic.

But stockpiling is not an uncommon reaction provoked by fear, social scientists say. Fear of running out. Fear of the unknown and what is to come.

After the 2011 earthquake and tsunami that devastated Japan, researchers at Hitotsubashi University studied buying patterns and concluded, “we can say that particularly anxious households appear to have bought anything that they could lay their hands on.”

Including lots of toilet paper.

Now, the lack of toilet paper in the United States has hit some Giant supermarkets and Costco stores. Amazon appeared to be down to single rolls of novelty toilet paper in some places Friday.

The shortages appeared to be sporadic and regional, with the degree of local concern about the pandemic driving sales.

But the nation’s lack of toilet paper is expected to be brief, according to interviews with retailers and manufacturers.

The sudden surge in demand is expected to subside and the supply will continue to grow as companies keep making toilet paper. About 90 percent of the toilet paper sold in the United States is made here, too, according to industry data.

“We continue to manufacture and ship Charmin to our retailers,” a Procter & Gamble spokesman said in a statement, adding the firm has noticed the sale spike and was working to fix availability problems.

But that still means some empty shelves, for now.

“Due to overwhelming demand, we are currently experiencing shortages and out of stocks on many household staples,” said Ashley Flower, public relations manager at the Giant Co., which runs 186 grocery stores in Pennsylvania, Maryland, Virginia and West Virginia. “We are focused on getting back in stock as soon as possible.”

But toilet paper has not disappeared entirely from stores. Ample supplies were available midday Friday at Snider’s Super Foods in Silver Spring, said manager Alex Xenochristos.

“We’ve been able to keep up with demand,” he said. “But I don’t know for how long.”