Stay home unless you must see a doctor. No trips to the office or school, no shopping. If you must come out of your room, wear a mask. And don’t share towels.

If you are among the thousands of Americans now self-quarantined because of possible infection with the coronavirus, these are a few of the new house rules, courtesy of your local health officials and the Centers for Disease Control and Prevention.

Self-quarantine and self-isolation are different. The first measure is for the large numbers of healthy people who may fall sick following possible exposure. The second is for people who are ill with the coronavirus — they are a danger to their family and visitors, and must be watched carefully in case they deteriorate.

At the moment, with testing still scarce in much of the country, it is hard for many Americans to know whether they are infected or just being prudent.

State and local governments generally have the power not just to advise quarantine but to order it. The circumstances under which they do so may change frequently, as the perceived threats change.

Countries around the world have instituted bans for travelers, many of which include requiring or requesting that travelers self-quarantine on their arrival. (In the United States, state-by-state travel is also being scrutinized.)

A growing number of people are self-quarantining because they were exposed to a friend or colleague who is sick. Millions of other Americans have also been asked to stay in and venture out only for necessities in an effort to stem the disease’s spread.

It may sound like a vacation from reality, an ideal time to binge on Netflix and catch up on sleep. In fact, it’s not easy to lock yourself away from family and friends. There are practical and logistical challenges, and yawning gaps in the official advice that make it even harder.

Home quarantine can be unpleasant and will probably last for two weeks, which is the presumed incubation period for the virus. It is especially challenging if you have young children or elderly relatives to care for, or live in cramped quarters with a lot of roommates.

The basics

Separation If you are potentially infectious, it is important that you separate yourself from your partner, your housemates, your children, your elderly aunt. To be on the safe side, you shouldn’t even pet your dog, according to the C.D.C., although pets are not known to transmit the coronavirus.

A room must be designated for your exclusive use. A bathroom should be, too, if possible. Every surface you cough on or touch could become contaminated with the virus.

You should have no visitors, and keep three to six feet away from others. Don’t take the bus or subway, or even a taxi.

Masks If you must be around other people — in your home, or in a car, because you’re on your way to see a doctor (only after you have called) — you should wear a mask, and everyone else should, too.

But first, you or one of your friends or family members have to find masks, which are sold out almost everywhere. If you can’t, you can create a makeshift one from a scarf or other garment.

Hygiene If you cough or sneeze, you should cover your mouth and nose with a tissue, and discard the used tissue in a lined trash can. Then you must immediately wash your hands with soap and water for at least 20 seconds.

You can use sanitizer, if you can find it, but soap and water are preferred.

Even if you haven’t coughed or sneezed, you should wash your hands frequently, and avoid touching your eyes, nose and mouth, if you haven’t just washed them.

Disinfect Don’t share dishes, drinking glasses, cups, eating utensils, towels or bedding with anyone (including your pets). Wash these items after you use them.

Countertops, tabletops, doorknobs, bathroom fixtures, toilets, phones, keyboards, tablets and bedside tables are considered “high-touch surfaces” — wipe them often with a household cleanser.

Frequently wipe down surfaces that may be contaminated by bodily fluids, including blood and stool.

Monitoring Keep an eye on your health and call a doctor if you develop symptoms or if they worsen. Make sure to tell the medical staff that you are at risk of infection with the coronavirus.

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Household members Housemates can go to work or school, but it’s going to be their job to stock up on groceries, pick up prescriptions, take care of the quarantined and keep the place clean.

They’ll be wiping down doorknobs and countertops, doing loads of laundry and washing their hands — a lot.

Family members and other occupants should monitor the patient’s symptoms and call a health provider if they see a turn for the worse.

When around a symptomatic patient, household members must wear a face mask, as well as gloves if they have contact with his or her bodily fluids. These should be thrown away immediately, never reused.

Elderly members of the household and those with chronic medical conditions risk severe complications, even death, if they become infected. Pregnant women may also be at particular risk, although the data aren’t clear. Contact with the secluded individual should be minimized.

In China, 70 to 80 percent of transmission occurred within family clusters, according to the World Health Organization. Local governments there were forced to set up isolation wards with thousands of beds in gymnasiums and stadiums to care for people who lived alone or were at risk of infecting their families.

Family members should monitor their own health, and contact a doctor if they develop a cough, fever or shortness of breath, signs of Covid-19, the technical name of the illness caused by the coronavirus. Please call first, so the office can prepare for your visit or direct you to a more appropriate site for care.

Unanswered questions

Not everyone can work remotely, and a two-week absence from work can take an enormous financial toll on hourly wage workers who have to clock in and show up to get paid, or who are part of the gig economy with no single employer.

However, included in the new $ 2 trillion stimulus package is jobless aid for many of those required to quarantine. (Who qualifies, how much aid can be collected and more information about the stimulus plan can be found here.)

There is no reimbursement for products you may need, no government home aide to stop by and help out. (Some states, like Washington, are attempting to provide limited assistance.)

Self-quarantine is a hardship, both emotional and financial, for those who have families and those who live alone.

“We have to have social interventions to incentivize and support isolation, or we are doomed,” said Arthur Caplan, professor of bioethics at New York University Langone Medical Center.

People with no health insurance, inadequate insurance or no regular doctor will be reluctant to seek care if they have symptoms, fearing steep medical bills, he noted. Undocumented individuals, fearful of being discovered and deported, may avoid diagnosis and care.

Major health insurers have said they will waive out of pocket costs for testing and treatment, according to administration officials, and Medicare and Medicaid also will cover the costs.

Providing for people who make sacrifices for the greater good is crucial, said Lawrence Gostin, a law professor at Georgetown University and director of the World Health Organization Collaborating Center on National and Global Health Law.

“We ought to have a social compact: If you’re sick, whether you’ve got Covid-19 or not, you should separate yourself from society,” Mr. Gostin said. “That’s your part of the bargain, you’re doing it for your neighbors, your family and your community.”

“In exchange,” he said, “we as a nation owe you the right to a humane period of separation, where we meet your essential needs like medicine, health care, food and sick pay.”