Preventing the spread of the coronavirus

Physical distancing, masks, and other preventive measures

You've gotten the basics down: you're wearing your mask, avoiding crowds, and keeping your distance from friends and family. But you likely still have questions. Does wearing a mask protect you, others, or both? How exactly will physical distancing help? And what do you need to know about the new COVID-19 vaccines?

Visit our Coronavirus Resource Center for more information on coronavirus and COVID-19.

What can I do to protect myself and others from COVID-19?

The following actions help prevent the spread of COVID-19, as well as other coronaviruses and influenza:

  • Wear a face mask.
  • Maintain at least six feet of distance between yourself and others.
  • Avoid large gatherings.
  • Socialize outdoors.
  • Avoid close contact with people who are sick.
  • Minimize touching your eyes, nose, and mouth.
  • Stay home when you are sick.
  • Cover your cough or sneeze with a tissue, then throw the tissue in the trash.
  • Clean frequently touched objects and surfaces regularly.
  • Wash your hands often with soap and water.
  • Get vaccinated as soon as you are eligible.

This chart illustrates how protective measures such as limiting travel, avoiding crowds, social distancing, and thorough and frequent handwashing can slow down the development of new COVID-19 cases and reduce the risk of overwhelming the health care system.

What do I need to know about washing my hands effectively?

Wash your hands often with soap and water for at least 20 seconds, especially after going to the bathroom; before eating; after blowing your nose, coughing, or sneezing; and after handling anything that's come from outside your home.

  • If soap and water are not readily available, use an alcohol-based hand sanitizer with at least 60% alcohol, covering all surfaces of your hands and rubbing them together until they feel dry.
  • Always wash hands with soap and water if hands are visibly dirty.
  • The CDC's handwashing website has detailed instructions and a video about effective handwashing procedures.

How does coronavirus spread?

The coronavirus spreads mainly from person to person. This can happen between people who are in close contact with one another. Droplets that are produced when an infected person coughs or sneezes may land in the mouths or noses of people who are nearby, or possibly be inhaled into their lungs.

A person infected with coronavirus — even one with no symptoms — may emit aerosols when they talk or breathe. Aerosols are infectious viral particles that can float or drift around in the air for up to three hours. Another person can breathe in these aerosols and become infected with the coronavirus. This is why everyone should wear a mask when they go out in public.

The risk of spread from contact with contaminated surfaces or objects is considered to be low. According to the CDC, each contact with a contaminated surface has less than a 1 in 10,000 chance of causing an infection.

The virus may be shed in saliva, semen, and feces; whether it is shed in vaginal fluids isn't known. Kissing can transmit the virus. Transmission of the virus through feces, or during vaginal or anal intercourse or oral sex, appears to be extremely unlikely at this time.

How could contact tracing help slow the spread of COVID-19?

Anyone who comes into close contact with someone who has COVID-19 is at increased risk of becoming infected themselves, and of potentially infecting others. Contact tracing can help prevent further transmission of the virus by quickly identifying and informing people who may be infected and contagious, so they can take steps to not infect others.

Contact tracing begins with identifying everyone that a person recently diagnosed with COVID-19 has been in contact with since they became contagious. In the case of COVID-19, a person may be contagious 48 to 72 hours before they started to experience symptoms.

The contacts are notified about their exposure. They may be told what symptoms to look out for, advised to isolate themselves for a period of time, and to seek medical attention as needed if they start to experience symptoms.

What is physical distancing and why is it important?

The COVID-19 virus primarily spreads when one person breathes in droplets or aerosols that are produced when an infected person coughs, sneezes, talks, or breathes.

Physical distancing refers to actions taken to stop or slow down the spread of a contagious disease. For an individual, it refers to maintaining enough distance (6 feet or more) between yourself and another person to avoid getting infected or infecting someone else. School closures, directives to work from home, library closings, and cancelling meetings and larger events help enforce physical distancing at a community level.

Slowing down the rate and number of new coronavirus infections is critical to reduce the risk that large numbers of critically ill patients cannot receive life-saving care.

What does the CDC's new definition of "close contacts" mean for me?

The CDC has expanded how it defines close contacts of someone with COVID-19. Until this point, the CDC had defined a close contact as someone who spent 15 or more consecutive minutes within six feet of someone with COVID-19. According to the new definition, a close contact is someone who spends 15 minutes or more within six feet of a person with COVID-19 over a period of 24 hours.

Close contacts are at increased risk of infection. When a person tests positive for COVID-19, contact tracers may identify their close contacts and urge them to quarantine to prevent further spread. Based on the new definition, more people will now be considered close contacts.

Many factors can affect the chances that infection will spread from one person to another. These factors include whether or one or both people are wearing masks, whether the infected person is coughing or showing other symptoms, and whether the encounter occurred indoors or outdoors. Though the "15 minutes within six feet rule" is a helpful guideline, it's always best to minimize close interactions with people who are not members of your household.

The CDC's new definition was influenced by a case described in the CDC's Morbidity and Mortality Weekly Report in which a correctional officer in Vermont is believed to have been infected after being within six feet for 17 non-consecutive minutes of six asymptomatic individuals, all of whom later tested positive for COVID-19.

What types of medications and health supplies should I have on hand for an extended stay at home?

Try to stock at least a 30-day supply of any needed prescriptions. If your insurance permits 90-day refills, that's even better. Make sure you also have over-the-counter medications and other health supplies on hand.

Medical and health supplies

  • prescription medications
  • prescribed medical supplies such as glucose and blood-pressure monitoring equipment
  • fever and pain medicine, such as acetaminophen
  • cough and cold medicines
  • antidiarrheal medication
  • thermometer
  • fluids with electrolytes
  • soap and alcohol-based hand sanitizer
  • tissues, toilet paper, disposable diapers, tampons, sanitary napkins
  • garbage bags.

What precautions can I take when grocery shopping?

The coronavirus that causes COVID-19 is primarily transmitted through droplets containing virus, or through viral particles that float in the air. The virus may be breathed in directly and can also spread when a person touches a surface or object that has the virus on it and then touches their mouth, nose, or eyes. There is no current evidence that the COVID-19 virus is transmitted through food.

Safety precautions help you avoid breathing in coronavirus or touching a contaminated surface and touching your face.

In the grocery store, maintain at least six feet of distance between yourself and other shoppers. Wipe frequently touched surfaces like grocery carts or basket handles with disinfectant wipes. Avoid touching your face. Wearing a cloth mask helps remind you not to touch your face and can further help reduce spread of the virus. Use hand sanitizer before leaving the store. Wash your hands as soon as you get home.

If you are older than 65 or at increased risk for any reason, limit trips to the grocery store. Ask a neighbor or friend to pick up groceries and leave them outside your house. See if your grocery store offers special hours for older adults or those with underlying conditions. Or have groceries delivered to your home.

Which precautions are really necessary when it comes to preventing COVID-19?

Wear masks. Physically distance. Socialize outdoors. Avoid crowded indoor spaces. Wash your hands frequently. These are essential precautions you should take to reduce your risk of catching or spreading coronavirus.

But what about some other precautions you may be taking? Do they help, or is it okay to let them go? Let's take a look.

You don't need to wear gloves when running errands. It's true that a person can get infected if they touch a surface or object that has viral particles on it, then touch their mouth, nose, or eyes. But this is not the main way the virus spreads. What's more, gloves won't prevent this type of transmission, and may even make it more likely that you will touch your face. Instead, wash your hands before you leave the house, use hand sanitizer when you're out and about, and wash your hands again when you get back home. In between, try to avoid touching your face.

You don't need to disinfect groceries or takeout containers. The risk of infection from food or food packaging is very small. The CDC advises against using disinfectant intended for hard surfaces on cardboard or other grocery items, which can absorb the chemicals. If you are concerned about takeout, transfer food to your own serving dishes. And wash your hands and disinfect your counters after putting away your groceries or handling takeout containers.

Your mail can come out of quarantine. Mail does not pose a large risk, and putting your mail aside for several days before opening it is unnecessary. Once again, your best bet is to wash your hands after handling anything you bring in from outside.

You can invite your cleaners back into your home. If you've asked your cleaners to come back, request that they wear masks the entire time they are in your home. Leave the house while the cleaners are present if you can; otherwise, move to a different part of the house and close the door. Open windows to increase airflow throughout the house.

It's okay to go for a swim. Pools are relatively safe, because the coronavirus doesn't spread through water and chlorine is a disinfectant. Try to maintain physical distancing in crowded pools, but don't wear cloth masks in the water: they are difficult to breathe through when wet. Do wear a mask when changing, however, and minimize time in changing rooms, which are often crowded and not well ventilated.

What can I do when social distancing?

Try to look at this period of social distancing as an opportunity to get to things you've been meaning to do.

Though you might be avoiding the gym right now, that doesn't mean you can't exercise. Take long walks or run outside (do your best to maintain at least six feet between you and non-family members when you're outside). Do some yoga or other indoor exercise routines when the weather isn't cooperating.

Kids need exercise too, so try to get them outside every day for walks or a backyard family soccer game (remember, this isn't the time to invite the neighborhood kids over to play).

Pull out board games that are gathering dust on your shelves. Have family movie nights. Catch up on books you've been meaning to read, or do a family read-aloud every evening.

It's important to stay connected even though we should not do so in person. Keep in touch virtually through phone calls, Skype, Zoom, video, and other social media. Enjoy a leisurely chat with an old friend you've been meaning to call.

If all else fails, go to bed early and get some extra sleep!

Should I wear a face mask?

The CDC now recommends that all adults and children over 2 years wear a mask when going out in public.

The coronavirus that causes COVID-19 is primarily transmitted through droplets containing virus, or through viral particles that float in the air. Even people who are infected but do not have symptoms, or have not yet developed symptoms, can infect others. Masks help minimize spread. They are to be used in additon to, not instead of, physical distancing.

What kind of mask should you wear? The CDC recommends masks made of two or more layers of washable, breathable fabric. Surgical masks are also effective, but pay attention to whether there is enough supply for front-line workers and emergency responders in your community. Make sure the mask completely covers your nose and mouth and fits snugly against the sides of your face without leaving any gaps.

While N95 masks are the most effective, these medical-grade masks should be reserved for healthcare workers.

Surgical masks are preferred if you are caring for someone who has COVID-19.

The CDC has information on how to make, wear, and clean nonsurgical masks.

The WHO offers videos and illustrations on when and how to use a mask.

Lately I've seen more people wearing two masks. Should I be double masking?

According to new guidance from the CDC, yes you should. The guidance is based on a lab study, published in MMWR, which used masked and unmasked dummies that released aerosol particles from a mouthpiece when they were simulated to cough or breathe. The study found that wearing a multilayered cloth mask over a surgical mask or wearing a tightly fitted surgical mask substantially increased the level of protection for both the mask wearer and others.

When double masking, the CDC recommends wearing a snug cloth mask over a surgical mask. Surgical masks provide better filtration, but tend to fit loosely. Cloth masks close any gaps and provide another layer of protection. Surgical masks are sometimes called medical masks or medical procedure masks.

Adjusting a surgical mask for a tighter fit using a method called "knotting and tucking" also offers good protection. To knot and tuck a surgical mask, knot the ear loops of a 3-ply face mask where they join the edge of the mask, then fold and tuck the unneeded material under the edges. For video instructions on how to knot and tuck a surgical mask, click here. Mask fitters, or mask braces, which are worn over a cloth or surgical mask, can also improve mask fit.

In the CDC's lab study, double masking or tight-fitting surgical masks reduced both transmission of and exposure to aerosols by about 95% compared to no masking.

What types of masks are most and least effective?

We know that wearing masks can help prevent the spread of coronavirus by blocking droplets that are emitted when someone coughs, sneezes, talks, or breathes. But which masks are best and worst?

Researchers at Duke University created a simple setup that allowed them to count the number of droplet particles released when people spoke the phrase "Stay healthy, people" five times in a row. First, the study participants spoke without a mask, and then they repeated the same words, each time wearing one of 14 different types of face masks and coverings.

As expected, medical grade N95 masks performed best, meaning that the fewest number of droplets got through. They were followed by surgical masks. Several masks made of polypropylene, a cotton/propylene blend, and 2-layer cotton masks sewn in different styles also performed well.

Gaiters ranked dead last. Also called neck fleeces, gaiters tend to be made of lightweight fabric and are often worn by athletes. Bandanas also ranked poorly.

A couple of simple tests can help you gauge the effectiveness of your mask: If you can see through your mask when you hold it up to the light, or can breathe through it easily, it's probably not doing much to prevent spread.

Who do masks protect: the wearer, others, or both?

We've known for some time that masks help prevent people from spreading the coronavirus to others. Based on an analysis of existing information, a new study contends that masks may also protect mask wearers from becoming infected themselves.

Different masks, writes the study author, block viral particles to varying degrees. If masks lead to lower "doses" of virus being inhaled, then fewer people may become infected, and those who do may have milder illness.

Researchers in China experimented with hamsters to test the effect of masks. They put healthy hamsters and hamsters infected with SARS-CoV-2 (the COVID-19 coronavirus) in a cage, and separated some of the healthy and infected hamsters with a barrier made of surgical masks. Many of the "masked" healthy hamsters did not get infected, and those who did got less sick than previously healthy "maskless" hamsters.

A similar experiment cannot ethically be done in humans. But researchers have studied doses of flu virus and found that people who inhaled a higher dose of flu virus were more likely to get sick and experience symptoms. Observations of coronavirus outbreaks in processing plants and on cruise ships also support the idea that masks may help protect mask wearers.

Without more research, we can't be certain that masks protect the wearer. But we do know they don't hurt, and that they protect others.

Could wearing masks prevent COVID deaths?

According to a study published in the journal Nature Medicine, widespread use of masks could prevent nearly 130,000 of 500,000 COVID-related deaths estimated to occur by March 2021.

These numbers are based on an epidemiological model. The researchers considered, state by state, the number of people susceptible to coronavirus infection, how many get exposed, how many then become infected (and infectious), and how many recover. They then modeled various scenarios, including mask wearing, assuming that social distancing mandates would go into effect once the number of deaths exceeded 8 per 1 million people.

Modeling studies are based on assumptions, so the exact numbers are less important than the comparisons of different scenarios. In this study, a scenario in which 95% of people always wore masks in public resulted in many fewer deaths compared to a scenario in which only 49% of people (the self-reported national average of mask wearers) always wore masks in public.

This study reinforces the message that we can help prevent COVID deaths by wearing masks.

If I want to visit friends and family, does it matter whether we meet indoors or outdoors?

You are better off meeting friends and family outdoors. We know that coronavirus spreads when someone breathes in virus that an infected person emits through coughs or sneezes, or when they talk or breathe. Research has shown that in a confined, laboratory setting, droplets containing viral particles can remain afloat for eight to 14 minutes. Smaller infectious viral particles, called aerosols, can drift around in the air even longer.

Outdoors, air currents are more likely to scatter and dilute the virus, making transmission less likely than in a home, office, or other confined space with limited air circulation. Even outdoors, however, it's important to maintain a physical distance of at least six feet and wear a mask, to reduce risk even further.

Coronavirus also spreads when a person touches a contaminated surface and then touches their eyes, nose, or mouth. If you are participating in an outdoor gathering, bring your own foods, drinks, plates, and utensils.

Can the COVID-19 virus spread through air conditioning?

We don't know for certain if the COVID-19 virus spreads through air conditioning. But we do know that when it's hot and humid, people are more likely to stay indoors, with the windows closed — giving the virus more opportunity to spread.

Coronavirus spreads through droplets that an infected person emits through coughs or sneezes and through smaller, infectious viral particles that can drift around in the air for several hours. Outdoors, air currents can scatter and dilute the virus, making transmission less likely. You're more likely to inhale the virus indoors, with the windows closed, whether or not you have the air conditioning on.

If you must be indoors with anyone outside of your household, increase air circulation by keeping the windows open as much as possible.

Does vitamin D protect against COVID-19?

There is some evidence to suggest that vitamin D might help protect against becoming infected with, and developing serious symptoms of, COVID-19. We know, for example, that people with low vitamin D levels may be more susceptible to upper respiratory tract infections. One meta-analysis found that people who took vitamin D supplements, particularly those who had low vitamin D levels, were less likely to develop acute respiratory tract infections than those who didn't.

Vitamin D may protect against COVID-19 in two ways. First, it may help boost our bodies' natural defense against viruses and bacteria. Second, it may help prevent an exaggerated inflammatory response, which has been shown to contribute to severe illness in some people with COVID-19.

Our bodies make vitamin D when exposed to sunshine. Five to 10 minutes of sun exposure on some or most days of the week to the arms, legs, or back without sunscreen will enable you to make enough of the vitamin. Good food sources of vitamin D include fatty fish (such as tuna, mackerel, and salmon), foods fortified with vitamin D (such as dairy products, soy milk, and cereals), cheese, and egg yolks.

The recommended dietary dose of vitamin D is 600 IU each day for adults 70 and younger and 800 IU each day for adults over 70. A daily supplement containing 1,000 to 2,000 IU of vitamin D is likely safe for most people. For adults, the risk of harmful effects increases above 4,000 IU per day.

Is it safe to travel once I'm vaccinated? What if I'm not vaccinated?

Guidance from the CDC issued in April 2021 states that fully vaccinated people may travel more freely within the US. Travelers do not need to get COVID testing before or after travel and do not need to quarantine, unless required by local or state authorities.

The CDC is more cautious about international travel, noting the increased risk of variants in other countries, even for people who are fully vaccinated.

As a general rule, travel can increase your chance of spreading and getting COVID-19 if you are not vaccinated. The CDC recommends that unvaccinated travels get tested before and after domestic travel and self-quarantine for seven to 10 days after travel. They discourage unvaccinated people from travelling outside of the US.

All travelers should wear a mask that covers the nose and mouth, maintain a physical distance of six feet from others, avoid crowds, and wash hands often. Anyone who is sick or has tested positive for COVID-19 should not fly if at all possible.

Stay current on travel advisories from regulatory agencies.

Can a person who has been infected with coronavirus get infected again?

Natural immunity to COVID-19 is the protection that results from having been sick. But we don't know how long natural immunity lasts, or how strong it is. So can we count on natural immunity to protect us from reinfection? If so, for how long? Unfortunately, we don't know the answer to either of those questions.

There have been some confirmed cases of reinfection with COVID-19. In other words, a person got sick with COVID-19, recovered, and then became infected again. This is rare, but it can happen.

The CDC states that people who have gotten sick with COVID-19 may still benefit from getting vaccinated. For now, people are eligible to get the COVID-19 vaccine whether or not they were previously infected. Vaccination criteria may change in the future as scientists learn more about natural immunity after COVID illness.

It's also worth noting that someone who has been reinfected — even someone with no symptoms — has the potential to spread the virus to others. That means that everyone, even those who have recovered from coronavirus infection and those who have been vaccinated, should continue to wear masks, practice physical distancing, and avoid crowds.

What is herd immunity, and could it play a role in stopping the spread of COVID-19?

Herd immunity occurs when enough people become immune to a disease to make its spread unlikely. As a result, the entire community is protected, even those who are not themselves immune. Herd immunity is usually achieved through vaccination, but it can also occur through natural infection.

Experts initially estimated that somewhere between 60% and 70% of the population needs to be immune in order to achieve herd immunity. More recently, they have raised that estimate to near 90%. (As of now, we are nowhere close to the numbers needed to achieve herd immunity.)

Achieving herd immunity through natural infection means many people would become ill and many would die. These risks may fall as we develop effective treatments. However, we still don't know how long people who recover from COVID-19 will remain immune to reinfection.

Ideally, we will achieve herd immunity as more people around the world receive vaccines that will confer lasting immunity.

Will a pneumococcal vaccine help protect me against coronavirus?

Vaccines against pneumonia, such as pneumococcal vaccine and Hemophilus influenza type B (Hib) vaccine, only help protect people from these specific bacterial infections. They do not protect against any coronavirus pneumonia, including pneumonia that may be part of COVID-19. However, even though these vaccines do not specifically protect against the coronavirus that causes COVID-19, they are highly recommended to protect against other respiratory illnesses.

Can my pet infect me with the virus that causes COVID-19?

At present, it is considered unlikely that pets such as dogs or cats can spread the COVID-19 virus to humans. However, pets can spread other infections that cause illness, including E. coli and Salmonella, so wash your hands thoroughly with soap and water after interacting with pets.

Can people infect pets with the COVID-19 virus?

The virus that causes COVID-19 does appear to spread from people to pets, according to the FDA. Research has found that cats and ferrets are more likely to become infected than dogs.

If you have a pet, do the following to reduce their risk of infection:

  • Avoid letting pets interact with people or animals that do not live in your household.
  • Keep cats indoors when possible to prevent them from interacting with other animals or people.
  • Walk dogs on a leash maintaining at least six feet from other people and animals.
  • Avoid dog parks or public places where a large number of people and dogs gather.

If you become sick with COVID-19, restrict contact with your pets, just like you would around other people. This means you should forgo petting, snuggling, being kissed or licked, and sharing food or bedding with your pet until you are feeling better. When possible, have another member of your household care for your pets while you are sick. If you must care for your pet while you are sick, wash your hands before and after you interact with your pets and wear a face mask.

What can I do to keep my immune system strong?

Your immune system is your body's defense system. When a harmful invader — like a cold or flu virus, or the coronavirus that causes COVID-19 — gets into your body, your immune system mounts an attack. Known as an immune response, this attack is a sequence of events that involves various cells and unfolds over time.

Following general health guidelines is the best step you can take toward keeping your immune system strong and healthy. Every part of your body, including your immune system, functions better when protected from environmental assaults and bolstered by healthy-living strategies such as these:

  • Don't smoke or vape.
  • Eat a diet high in fruits, vegetables, and whole grains.
  • Take a multivitamin if you suspect that you may not be getting all the nutrients you need through your diet.
  • Exercise regularly.
  • Maintain a healthy weight.
  • Control your stress level.
  • Control your blood pressure.
  • If you drink alcohol, drink only in moderation (no more than one to two drinks a day for men, no more than one a day for women).
  • Get enough sleep.
  • Take steps to avoid infection, such as washing your hands frequently and trying not to touch your hands to your face, since harmful germs can enter through your eyes, nose, and mouth.

Should I go to the doctor or dentist for nonurgent appointments?

Many medical and dental practices have instituted comprehensive safety measures to help protect you, the doctor and office staff, and other patients. If you feel anxious about visiting in person, call the practice.

Many doctor's offices are increasingly providing telehealth services. This may mean appointments by phone call, or virtual visits using a video chat service. Ask to schedule a telehealth appointment with your doctor for a new or ongoing nonurgent matter. If, after speaking to you, your doctor would like to see you in person, he or she will let you know.

What if your appointments are not urgent but also don't fall into the low-risk category? For example, if you have been advised to have periodic scans after cancer remission, if your doctor sees you regularly to monitor for a condition for which you're at increased risk, or if your treatment varies based on your most recent test results? In these and similar cases, call your doctor for advice.

Should I postpone my elective surgery?

The availability of elective surgeries and procedures throughout the United States is very fluid, and may reflect the number of cases and infection rate in a given area. If COVID-19 cases are rising in your area, it's quite possible that you already have been canceled or rescheduled by the hospital or medical center in which you are scheduled to have the procedure. If not, then you should consider postponing any procedure that can wait.

That being said, keep in mind that "elective" is a relative term. For instance, you may not have needed immediate surgery for sciatica caused by a herniated disc. But the pain may be so severe that you would not be able to endure postponing the surgery for weeks or perhaps months. In that case, you and your doctor should make a shared decision about proceeding.

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