Why Testing Matters

How diseases spread, who's at highest risk, and what the latest COVID rules are for travel.

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How Disease Spreads and Who's at Risk
Travel
Work and Kids

How Disease Spreads and Who's at Risk

How does COVID spread?

The virus that causes COVID moves through the air on tiny bits of water from people who are infected. You get COVID by breathing the virus in. The more virus you breathe in, the more likely you are to get sick. The video shows how that happens. (Animation by Vicki Martin, University of Oxford)

Some of the smallest bits of moisture that the virus rides on are called aerosols. We release aerosols when we sneeze, cough, talk, or even breathe.

Illustration showing the relative distance virus particles can travel to infect someone. Particles on large droplets fall more quickly but can infect people who are close. Particles on large aersoles can drift farther, and small aerosoles, farther yet.

This illustration, published by professor Linsey Marr, shows how aerosols move through the air in a room without good air flow. They can be breathed in even by someone standing far away.

Video: Aerosol transmission of COVID-19

How does flu spread?

We know that flu can spread on droplets of water that people breathe out when they sneeze, cough, talk, or breathe. Those droplets don't travel far through the air before they fall to the ground.

Flu may also spread through tiny bits of moisture called aerosols that people also breathe out. It's also possible that you can get the flu from touching something that an infected person has touched and then touching your own mouth, nose, or eyes.

Who is most likely to get very sick from COVID and/ or flu?

People over age 65 are at high risk of getting very sick from both COVID and flu. So are people whose immune systems are not strong, including pregnant people.

Children under age 5 are at high risk of getting very sick with flu. They're more likely to have a mild case of COVID.

Other health conditions can put you at high risk for one or both of these diseases. The more conditions you have, the higher your risk is.

COVID: Conditions that put you at high risk
Flu: Conditions that put you at high risk

I've been exposed to someone who had COVID. Do I need to test?

You don't have to test yourself right away, but you do have to start wearing a high-quality, well-fitted mask any time you're around other people. That includes people in your household. You'll need to keep masking for 10 days after your exposure. That will help keep you from spreading the virus if you're infected but don’t have symptoms. Don't travel anywhere if you can't wear good mask whenever you're on public transportation or around other people indoors in public.

Wear a mask with the best fit, protection, and comfort for you. Graphic from the cdc.gov/coronovirus

N95 and KN95 masks (also called respirators) are the best at protecting you from COVID. They also help protect you against flu.

If you don't have any symptoms, wait at least 5 days after you were exposed and then get tested. If you're using a rapid test and you test negative, the safest thing to do is to test yourself two more times, with 48 hours between each test.
If you get symptoms, isolate yourself and get tested as soon as you can. Stay home and masked until you know the results. If you're using a rapid test and you test negative, the safest thing to do is to continue to isolate and test yourself again in 48 hours. If you test negative a second time, you can end isolation but should continue to mask until the full 10 days are up.

Whenever you use a rapid test, report your result at MakeMyTestCount.org — whether you test positive or negative.

Travel

Do I still need to test for COVID before I travel?

You don't need to test before travel unless you have COVID symptoms.

If you were recently exposed to someone who has COVID

Don't travel if you can't wear good mask whenever you're around other people indoors in public or on public transportation. You'll need to wear a high-quality, well-fitted mask if you're around others for 10 days after your exposure. That will help keep you from spreading the virus if you're infected but don’t have symptoms.
You should test at least 5 days after you were exposed. If you test too early, your result might not be right.
If you're using a rapid test and you test negative, the safest thing to do is to test yourself two more times, with 48 hours between each test.
If possible, you may want to postpone your travel until after you're sure you don't have the virus.

N95 and KN95 masks (also called respirators) are the best at protecting you from COVID. They also help protect you against flu.

When can I travel after testing positive?

Each time you use a home test for COVID, report your result at MakeMyTestCount.org — whether you test positive or negative.

If you had symptoms, you can travel once 5 full days have passed since your positive test, as long as:

You're feeling better, and
You're fever-free without using medication, and
You can wear a good mask whenever you're around people indoors in public and on public transportation.

If you did not have any symptoms, you can travel after 5 full days have passed since your positive test, as long as you can wear a good mask whenever you're around people indoors in public and on public transportation.

Learn more about when you can stop isolating.

Where can I find a COVID test before I travel?

You can find a free testing site near you on the CDC's No-Cost COVID Testing locator. Tests available at these sites may be rapid tests or PCR tests.
Uninsured or underinsured adults can get free at-home tests and access to telehealth appointments through the US government's Home Test to Treat program.
If you need a PCR test you can get low- or no-cost testing at community health centers and pharmacies around the US. (Find a community-based testing location here.)
You may be able to get free tests through your local health department.
The Rockefeller Foundation's Project ACT program is offering free at-home COVID tests to individuals in certain ZIP codes while supplies last.

Do I need take a COVID test after I come home from traveling? If so, when?

If you spent time without a mask in crowded places, especially indoors, consider getting tested when you come home from a trip. That's especially important if COVID levels were high in the place you visited.

Take the test at least five days after the last time you were in a crowded place without a mask.
If you get symptoms before then, go ahead and test right away.
If you test negative on a rapid test, test yourself again 48 hours later. To be safest, take a third test 48 hours after that.
Each time you use a rapid test, report your result — whether you test positive or negative.

Do I need to test for COVID before I travel to another country?

Very few countries require travelers to test before entering. However, some change their policies when surges happen.

The US government no longer tracks this information. As a starting point, you can check a travel site such as Sherpa or Wego for maps or lists of countries that require COVID testing for entry. Be aware that things may have changed since these sites were last updated, though. If you want to be sure, contact the US embassy for your destination.

Do I need to take a COVID test to get back into the US from another country?

You don't have to test before coming into the US. But if you spent time without a mask in crowded places during your trip, especially indoors, consider getting tested when you come home from a trip. That's especially important if COVID levels were high in the place you visited.

Take the test at least five days after the last time you were in a crowded place without a mask.
If you get symptoms before then, go ahead and test right away.
If you test negative on a rapid test, test yourself again 48 hours later. To be safest, take a third test 48 hours after that.

Each time you use a rapid test, report your result — whether you test positive or negative.

Work and Kids

I have COVID symptoms. Should I test before I go to work?

If you have COVID symptoms, you should isolate and get tested before you go to work or are around other people. If you have to be around other people, wear a mask until you get your result.

Each time you use a rapid test, report the result — whether you test positive or negative.

If you test positive

You should isolate and consider treatment.

If you test negative on a rapid test

That’s good news, but your condition might change. After you’ve been exposed to COVID, it takes a few days for enough virus to grow in your body that you test positive.
To be safer, test again at least 48 hours later and wear a mask around others until then. Make sure to follow all of the instructions that come with the test.
You can also get a lab test to confirm your result.

I was exposed to someone who has COVID. Should I test before I go to work?

If you don't have any COVID symptoms, you don't have to stay home unless your workplace requires it.

You'll need to get tested 5 days after your contact, and you'll need to wear a mask around others for a while. Learn more about what to do when you've been exposed.

Each time you use a rapid test, report the result — whether you test positive or negative.

My child was exposed to someone who has COVID. Should I test them before they go to school?

If your child doesn't have any COVID symptoms, they don't have to stay home unless their school requires it.

Your child will need to get tested 5 days after their contact, and they'll need to wear a mask around others for a while. Learn more about what to do if you're child was exposed.

Each time you use a rapid test, report the result — whether you test positive or negative.