New York has become Ground Zero for coronavirus, with the number of deaths doubling in three days. On Friday, the state’s COVID-19 fatalities edged close to 3,000, surpassing the number of people who died here on 9/11. The number of confirmed cases in the state rose by 10,000 overnight to 102,863. “It’s hard to go through this all day, and then it’s hard to stay up all night, watching those numbers come in and the number of deaths tick up,” New York Gov. Andrew Cuomo said.

People have longed for clarity on how to keep themselves and everyone else safe. On Thursday evening, something else happened. (Something always happens.) New York City Mayor Bill de Blasio went one step further and said all New Yorkers should wear cloth masks. “You can create a face covering with anything you have at home right now, a piece of cloth,” he said. (Others say two layers of cotton or paper towels have enough density to protect against the virus.)

Like Trump and the CDC, de Blasio said that he does not recommend using N95 masks. “We’re advising New Yorkers to wear a face covering when you go outside and will be near other people. Let’s be clear, this is a face covering. It could be a scarf, it could be a bandana, something you create yourself. It does not need to be a professional surgical mask.” You know what’s better than a bandana, covers more of your face and stays in place? A balaclava.

This week, I went to a grocery store and I improvised in a balaclava. At the time, it seemed like a weird thing to do. I looked like the Invisible Man if he had a walk-on role on “A Clockwork Orange” or “Mad Max,” as a friendly commentator said. Here’s why I wore it: I wanted to cover my face completely so (a) I wouldn’t touch it, (b) I could reduce my chances of catching a coronavirus-infected droplet and (c) I could protect others in case I was asymptomatic. (You could also make a balaclava out of a cotton sheet or an old hat.)

Cuomo told CNN’s Anderson Cooper Thursday night that “it couldn’t hurt from a public-health point of view” to wear improvised face masks to help stop the spread of coronavirus. Asked by Cooper whether he would follow de Blasio’s suggestion on face covers such as bandanas, Cuomo said, “It could help if someone has the virus.” He added, “It couldn’t hurt. It’s not exactly fashion forward.” That, of course, is the least of people’s worries.

There is evidence that some masks do work: Medical-grade N95 surgical masks, according to this study, filter viruses larger than 0.1 micrometers (a micrometer, um, is one millionth of a meter). The coronavirus is approximately 0.125 micrometer. Would my humble balaclava make a difference? I could be wrong, I could be right, as Johnny “Rotten” Lydon sang. But I wore one. Given de Blasio’s statement on Thursday evening, I’m glad I did.

Wearing a balaclava, the most effective cloth mask I have lying around, is not something I did lightly. Growing up in Ireland in the 1980s during the Troubles, and living in London during the 1990s, sporting a balaclava with an Irish accent would have been a risky proposition. It has connotations that no Irishman would like to relive. But with my now transoceanic twang, I think I’ll be OK. Plus, it’s for the opposite reason than Ireland of Yore: I want to stay safe and help others do the same.

Masks have helped reduce contagion by reducing droplets being sprayed into the air by the wearer. For the record, I would not wear a medical-grade mask. There is a shortage in hospitals in New York City, along with ventilators and other personal protective equipment. Here are some tips on how to make your own mask. For now, however, I will stick with my balaclava, and offer up this survival guide for food shopping in the epicenter of COVID-19 in the United States.

And, so, here’s my story of a trip to a New York grocery store

NEW YORK — One of my best friends in New York is self-quarantining, and she requires a friend or two to shop for her. I am down with spending other people’s money and I like to be helpful, especially when the entire country appears to be waiting for the dreaded surge of coronavirus cases. For me, this is a win-win. Also, she has good taste, so her shopping list will have plenty of ideas for me. I just discovered homemade peanut butter. I will never go back to jars again. That’s a win-win-win.

Not bad for a couple of hours’ work. This task also gives me the opportunity to give people a snapshot of what it’s like living in New York City, the city that these days always appears to sleep. We are the national epicenter of the coronavirus pandemic. I don’t have a yacht or a big pile in the country to retreat to. I love my adopted city, and I’m not going anywhere. I will ride this out. On that note, I have a 5-point survival guide for food shopping, which I hope is useful regardless of where you happen to live. So that’s a win-win-win-win.

So far, so good. We’re off to a good start. First off, here’s a little about my self-quarantining friend: She is smart, extremely well-read, and makes me laugh. We read long-form articles together and, afterwards, we discuss them over tea. We don’t always agree, which we like, but we do agree most of the time, especially on social issues, and we’re OK with that, too. She remains open to changing her mind. I learn from her, so I endeavor to remain open minded too.

Chapter 1. How to enjoy Dubliner cheese and crackers

My friend recalled the AIDS crisis of the 1980s and 1990s, and how people would get up from a park bench if they thought a sick person sat down next to them. New York was one of the epicenters of that pandemic, too. She did not get around to talking about the many polio epidemics America has faced throughout the 20th Century. There are only so many plagues a person wants to recall over a plate of Dubliner cheese and crackers. Look back, but stay present. A little perspective is good.

She may be stuck at home, but she remains upbeat, and doesn’t let the grass grow under her feet. It’s humbling to witness. We take tap-dancing classes together (her idea). At least, we did until the social-distancing policies prescribed by public-health officials came into effect. On Monday, we each vowed to practice 15 dance steps. That’s more “dig, brush, toe, heel, paddle and roll, paradiddle!” for me. Before tap-dancing class, she asks me, “So, Quentin, what color is your tutu today?” I usually describe the most ridiculous-sounding tutu. “Pink,” I say, “with yellow ruffles.”

My friend is 95, and she is now blind. Mostly, I feel grateful that we are both here in the same place, and at the same time, and that our paths crossed. She grew up in an Irish community in Massachusetts. I grew up in Dublin. She calls me “lace-curtain Irish.” Because she is in a high-risk group, she is isolating. There is so much that is out of our own control during this pandemic, but this I could control: I could go to the supermarket for her. That is how I found myself with another Irishman — who moved to the U.S. 30 years before I did — at the Fairway Market on Broadway and 74th Street on Monday afternoon, with a shopping list in one hand and a grocery cart in the other.

We’d both been asked to help buy our friend groceries — separately, it seemed — so we joined forces. I didn’t like him usurping my place as Sir Edmund Hillary on this potentially hazardous expedition. Nor did I want to be Francis Crozier to his Sir John Franklin. (Neither Crozier or Franklin returned from their last expedition to the Arctic.) It’s sometimes difficult to ask one person for what seems like a big favor. It can seem easier to ask two people for slightly smaller favors. Regardless, this is the time to ask. I was happy to share the load. We made a good team.

“If we get coronavirus, a grocery store is where we’ll get it!” I said, surveying the food aisles, and giving the gimlet eye to the scattering of other cautious New Yorkers wandering around in masks, pushing their carts. He looked at me like I was about to rob a store, not shop in one. I was wearing a balaclava I’d bought years before for a New Year’s Eve midnight run in Central Park. He tried to muffle a laugh. “Would you risk your life for a bagel?” I asked him. “How about a jar of marmalade?” I presumed that he was about to say, “You are overreacting! He smiled, instead.

Chapter 2. St. Dalfour is delicious, but is it worth it?

Earlier this week, I faced that dilemma. I was out of marmalade. I layered up and headed to Barney Greengrass on Amsterdam Avenue and 87th Street. This is the Jewish deli founded by the man who shipped smoked sturgeon to President Franklin D. Roosevelt in Warm Springs, Ga. for Thanksgiving 1939. I bought a jar of St. Dalfour French preserve. I forgot they only accept checks or cash. I fumbled theatrically for stray dollars. “We’ll take your number,” the man behind the counter hollered, “and bill you during the week!” That’s the New York I know and love.

After that trip to Barney Greengrass, I got the idea for a D.I.Y. mask to help me and others stay healthy: My balaclava. The New York City Department of Health said in an online statement that face coverings are more useful for protecting others if you are asymptomatic. “A face covering will not protect you from infection, but it can help others. A face covering can include anything that covers your nose and mouth, including dust masks, scarves and bandanas. Do not use health-care worker masks, as those must be preserved for people in the health-care system.”

I also wore woolen gloves to Fairway Market and Barney Greengrass because studies have found that shopping carts are covered in all kinds of germs, just like subway poles and turnstiles, or anything else that lots of people touch on a regular basis. I constantly lose my gloves, alas. But I have adopted a wartime thrift: Today, I wear odd pairs with pride. I did not bring alcohol wipes to Fairway. Next time, I will at least bring a few Clorox CLX, -1.20% wipes in a Ziploc bag. Before and after I put the groceries away, I wash my hands.

Chapter 3. Leave your ‘cranky pants’ in the dry cleaners

Coronavirus can reportedly survive longer on a solid surface like cardboard, steel or plastic than on a pair of gloves. That’s good news for my gloves, but I still act as if the virus could find its way onto my gloves, too. Here’s the other reason I wore a balaclava to the supermarket: It’s not comfortable, it reminds me and other people that we’re dealing with a serious health emergency; it covers almost my entire head, and — here’s the science bit — it provides a constant nudge to remind me: ‘Do not touch your face.’ If you take anything away from this, take that.

Shopping can be stressful under these conditions. It’s good to be a cautious — and a smart — shopper. I usually want to get in and out in double-quick time, but on this occasion I decided to be careful and take my time. What’s more, I enjoyed it. Everything I could have done to minimize my chances of picking up COVID-19, I did. I stayed 6 feet away from others, whenever possible, including my shopping partner. We did not go at rush hour. I talked to staff and other customers.

Everyone is freaked out. I get it. That’s why I decided to leave my “cranky pants” at the dry cleaners, which closed its doors shortly after Gov. Andrew Cuomo’s (N.Y., D.) social-distancing policy came into effect. Friendly banter puts me and, I hope, others at ease. A nice woman recommended the London broil. “Thanks for the tip,” I said. “I’ll take half a pound!” I may not know my broil from my flank, but I do have a pretty good idea where our weak spots are for the virus. I just have to keep my cool.

Chapter 4. ‘Good morning! Have a shatterproof day’

If you are concerned about going to the grocery store, imagine what it’s like for those who work there. They may smile and say, “Can I help you?” But they could also be thinking, ‘Do you have it?’ I told every staff member I spoke to at Fairway, “Thank you for working today.” They need to hear that. New Yorkers have read about the hospital naval ships arriving into New York Harbor on Monday. The sound of entire neighborhoods cheering for health-care workers can move you to tears. But not everyone is finding it so easy, and a frazzled customer is often not a gentle or happy customer.

I read peer-reviewed studies — not mysterious Facebook FB, -2.53% posts — and I don’t let them drive me crazy. There is still no evidence linking coronavirus transmission with food and food packaging, despite the virus being able to survive on cardboard in a laboratory setting. Furthermore, Juan Dumois, a pediatric infectious-diseases physician at Johns Hopkins All Children’s Hospital in St. Petersburg, Fla., suggests that viruses would survive better on “artificial fibers” — polyester over wool, silk or cotton.

Ultimately, I choose caremongering over scaremongering because fear is not your friend. My self-quarantining friend told me the other day, “Quentin, I’m 95! Do you think I’m scared of coronavirus?” But that doesn’t mean she’s standing in line at the supermarket, either. So here’s the deal: If you want to change clothes or wear a non-surgical mask, do it. If you want to wear a goldfish bowl on your head and fly around on rollerblades, while reciting “De Rerum Natura” by Lucretius, be my guest. I’ll be the first to tip my hat, and say, “Good morning! Have a shatterproof day.”

Chapter 5. The biggest supermarket sweep of all

I also got something I couldn’t buy at any store or pharmacy. Getting out of the house for a couple of hours was a great tonic. It was like magic. This was the biggest supermarket sweep of all: Turns out, my friend was doing me the favor, and I didn’t even know it. I did not see Yoko Ono rummaging through the vegetables at Fairway — I did see her there once, and I left her to it — but I did enjoy the fruits of my labor by feeling useful for helping a friend. I also met a neighbor outside. We stood from 6 feet away from each other. He works in a salon and he has been furloughed. New York is a village. Love and gratitude is all around.

And so to the last leg of my New Yorker’s survival guide to grocery shopping. We had two weeks’ worth of groceries — bottles, cans, six-packs of kitchen roll, liters of milk, jars of this, that and the other — and they were heavy. Remaining hypervigilant for an hour in the store made it seem more like two hours. We were both exhausted from our shopping. I walked one block, and we had a few more to go. I spotted an abandoned cart on the street corner. “We’ll return it,” I said. “Later!”

You have to think on your feet during a pandemic, and I wanted to get these goods to their destination without doing my back in. (That’s my excuse, anyway.) I quickly piled the groceries into the cart, and pushed it across four traffic lanes on Broadway. “Go! Go! Go!” I shouted, as we hurtled along. This was not a time for reticence. We’re in the middle of a national emergency, after all; if the cops stopped me, I’d simply tell them the truth. Thank you, NYPD, first responders and health professionals, and thank you, Fairway Market.

As I headed down Amsterdam with the speed of a bullet, a man ran out of a jewelry store in pursuit of another man. “People are dying, and you try to steal something from my store? You motherf—!” Ah, yes. There are always folks with bigger problems than mine. I kept moving: This was a good day in Manhattan. To quote that opening line from Jules Dassin’s postwar film noir, “The Naked City”: “There are 8 million stories in the naked city. This has been one of them.” My 95-year-old friend would have been about 22 when that film was released. She, too, has more stories to tell.

(This story was updated with a comments by Mayor de Blasio.)

This essay is part of a MarketWatch series, ‘Dispatches from a pandemic.’