As coronavirus cases mount, just how paranoid — or cautious — should we be?

The line between prudence and nervous Nellie-ism keeps shifting.

Yoshi Lu works out at home. Amid coronavirus concerns, Lu has stopped going to his gym for fear of germs.Jessica Rinaldi/Globe Staff

Are you too paranoid about coronavirus? Or not paranoid enough? Where’s the line, anyway? Is Yoshi Lu on the correct side of it? Is Katherine Ingraham?

Lu is a Medford man who has stopped going to the gym because even the spritz bottles used to clean the equipment seem suspect. “No one cleans the bottles themselves,” said Lu, a senior educator at the Gibson House Museum in Back Bay.

There’s no way for him to know where other gym members have traveled, or who they’ve been in contact with. “It’s ‘Six Degrees of Kevin Bacon,’ ” he said of the parlor game, corona version.

Ingraham is a Brookline interior design consultant with a joie de vivre attitude who is going ahead with a trip to London, even though her daughter’s choir canceled its UK tour.

“We are definitely going to pay attention to our environment,” she said, “but London seems to be business as usual and I don’t think it makes sense to put your life on hold.”

With coronavirus cases multiplying exponentially, and social norms changing rapidly, the border between prudence and nervous Nellie-ism, is moving fast. What might have seemed alarmist two weeks ago — beware the gas station’s self-serve nozzle because it might be contaminated — now sounds kind of wise.

We’re being told the risk in Massachusetts is low, but Harvard University is telling students to stay away from campus, and Boston has canceled its St. Patrick’s Day parade.

The stakes are so high. It’s not just about keeping yourself from getting sick, it’s about not spreading the illness to others. But in the face of scant specific advice from leaders, except to avoid cruise ships, Bostonians are wondering whose precautions should we follow?

MIT has banned events with more than 150 people. Does that mean it’s OK to go to wedding as long as the bride keeps the guest list to 149? What if a “no” RSVP comes after all?

The drug giant Takeda, with some 5,000 employees in Massachusetts, is telling workers who come to the office to keep six feet away from each other. Does that mean you can safely go to an intimate dinner party as long as you keep your distance from other guests? Can you toss the butter?

Starbucks has halted the use of reusable cups. So maybe you shouldn’t touch a water glass in a restaurant if the waiter who handles it isn’t wearing gloves? What if the gloves themselves are contaminated?

“I’m a mess of contradictions,” said writer Beth Jones. She’s stopped going to the public library “because it’s not well-ventilated,” but she’s also looking for international hotel deals. “I’m trying to figure out what to do on a minute-by-minute basis.”

The world is waiting to see where the spiraling epidemic will go, but one thing is already clear: We’ve definitely reached the judgment phase.

In Boston, an office worker who brought a towel soaked in bleach solution to sanitize his keyboard and phone scoffed when told of a woman who had bought a second freezer for supplies. As if her planning was over the top but his precautions weren’t.

“Is she expecting the siege of Leningrad?” he asked.

People downplaying the coronavirus’s danger are being accused of acting like Trump. People texting corona death reports to friends and family are being accused of fear mongering.

But the epidemic is so big, so scary, that many people are not only judging others but themselves.

In the span of one brief conversation at the Fenway Target on Sunday morning, Angela Marini, a project manager for a large Boston firm, criticized people for overreacting and then speculated she herself might go bananas.

“People are so crazy that soon we are going to run out of bottled water,” she said. Then, a few minutes later: “But talk to me in one month, I don’t know what I”ll tell you.”

As cancellations mount, costing people money and opportunities, a backlash is forming.

At Worcester Polytechnic Institute students unhappy that the school canceled travel for international projects have signed a petition on Change.org urging the school to allow the students to make their own decisions.

The coronavirus is as vast as the entire world, but also as tiny as the marital bedroom. Which is to say it has, of course, entered the family and marital counseling space. “People have different ideas about how much caution to exercise,” said Liz Brenner, a clinical social worker in Watertown.

Such is the divide that in one suburb, a wife is planning to hide hundreds of dollars of emergency supplies from her beloved. “I’m paying cash,” she said.

Oh, for the good old days, when people concealed designer handbags and expensive fishing reels from each other, and the scariest thing about a cruise was the weight gain.