When the country was largely under lockdown, at least the rules were mostly clear. Essential workers ventured out; everyone else sheltered in. Bars and restaurants were closed except for dining out; hair salons and spas were shuttered. Outings were limited to the supermarket or the drugstore.

Now states are lifting restrictions, but detailed guidance about navigating the minutiae of everyday life is still hard to come by — and anyway, there’s never going to be a ready solution to every problematic circumstance you may encounter.

“Ramping down was easy by comparison, even though it felt hard at the time; we basically flipped a switch,” said Dr. Preeti Malani, an infectious disease expert who is chief health officer for the University of Michigan. “Reopening is much more complicated. There is no template, no playbook. We can’t just say, ‘Follow these 10 rules, and you’re good.’”

Even in the absence of detailed directives, however, there’s scientific consensus about a general approach that can reduce the spread of the virus as the world around you reopens. As you tiptoe toward normalization — whatever that is, given these times — try to follow three precautions: avoid contact, confinement and crowds. And make realistic choices.

Contact

You need to continue with social distancing precautions. That means wearing masks, washing hands well and often, and keeping a distance of at least 6 feet from one another. No hugs, at least not in the usual way. No handshakes.

Try to make sure that public spaces you frequent are maintaining mitigation measures: spreading out tables at a restaurant, limiting or spacing out patrons in shops and parks, and conducting frequent cleaning and disinfection.

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The virus is spread most efficiently from person to person, but the Centers for Disease Control and Prevention nonetheless recommends frequent cleaning of high-touch objects and surfaces like tables, doorknobs, light switches, countertops, handles, phones, keyboards, toilets and faucets, touch screens, ATMs and gas pump handles.

Any 15-minute face-to-face conversation between people who are within 6 feet of each other constitutes close contact, said Dr. Muge Cevik, an expert on infectious diseases and virology at the University of St. Andrews School of Medicine in Scotland.

The longer the conversation and the closer the physical proximity between the participants, the greater the risk of the virus spreading if one person is infected.

That explains why transmission is rampant within households and why family gatherings where people embrace and spend a couple of hours together over a meal have led to outbreaks.

In one case investigated by federal health officials, an individual with mild respiratory symptoms attended a funeral in Chicago in February, setting off a chain of transmission that led to more than a dozen people getting sick and three deaths.

The individual was a family friend who embraced mourners at the service, spent a few hours sharing a takeout dinner and a potluck meal, and went to a family birthday party.

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As various relatives fell ill, household members who took care of them were also infected; birthday party guests who had contracted the virus went to church, infecting congregants sitting in the next row.

Altogether, 15 people were infected. The CDC has recommended limiting funerals to immediate family or holding virtual memorial services, depending on local transmission of the coronavirus.

Confinement

Indoor activities in confined enclosed spaces, even large ones, are more conducive to spreading the virus than events held outside, especially if the air inside the building is being recirculated or the windows don’t open.

Many infections have been traced to public transportation vehicles like buses and vans. Some experts have raised questions about the safety of enclosed public spaces, like office buildings, indoor restaurants and nightclubs.

“When there’s stagnant air, the droplets could persist longer than you would expect, and there will be a lot of contamination on surfaces,” Cevik said.

A flow of fresh air dilutes the virus, she added: “When you’re next to a good air flow source or by a window, your upper respiratory tract won’t be exposed to that much virus anymore.”

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Cevik referred to a study that traced a COVID-19 outbreak in China to a service at a Buddhist temple in Ningbo, in Zhejiang province, in January.

Some 300 people were at the service, which lasted 2 1/2 hours and included lunch. It was held outdoors, and most of the worshippers were not infected. And of the 30 people who were infected, most had traveled on the bus to the temple and back with the first person who became ill, about an hour’s drive each way.

On that bus, no one sitting by an open window got sick, with the sole exception of an individual who sat directly next to the infected woman.

In recent guidance to businesses that are reopening, the CDC told employers they must make sure ventilation systems are working properly and take steps to maximize the circulation of outdoor air by opening windows and doors and using fans.

Crowds

Large groups are risky no matter where they are gathered. Even outdoors, crowds mean more people, more contacts — and more potential sources of infection. And ultimately, preventing infection is a numbers game, where less is more.

“It’s a really different way of thinking that most people in the world aren’t used to,” said Dr. Barbara Taylor, an infectious disease specialist at the University of Texas Health Science Center at San Antonio. “It’s all math.”

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Many bars in Texas are outside, she noted, and are therefore relatively low risk. But the number of patrons in a space still matters.

“You can create a scenario where you have everybody 6 feet apart, but if that scenario involves 500 people, that is inherently more risky than if that same scenario involves 30 people,” Taylor said. “There’s more potential for one of those 500 people to have COVID-19 and be spreading it,” she said.

Another concern about drinking holes: As people become inebriated, they let their guard down and lose their inhibitions.

The CDC ranks dining options from lowest- to highest-risk situations. The lowest risk is a drive-thru, delivery, takeout or curbside pickup of food. Restaurants with the highest risk have indoor and outdoor seating with no additional spacing between tables.

Choices

Every individual ultimately must make a personal decision about the level of risk he or she is comfortable with, weighing their own age and health status, life circumstances and general level of risk aversion or tolerance.

People at high risk for developing severe disease if they become infected with the coronavirus will want to take the greatest of precautions. That group includes those 65 and older; residents of nursing homes and long-term care facilities; and people with compromised immune systems, with chronic lung or kidney disease or heart conditions, or who are severely obese.

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But young, healthy adults and children should also consider the protection of people around them, including family members, colleagues or friends who are vulnerable because of chronic disease or other life circumstances, Taylor said.

Her tolerance for risk is very low, she said. Although Taylor has no health problems, she is a physician who treats vulnerable and immunocompromised patients and also sees her parents regularly.

“We are our brothers’ keepers,” she said. “Although I’m not in a risk group, I’m regularly in contact with people who are, so it comes down to not just thinking about ourselves, but our whole communities, and how we all have to protect one another.”