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COVID-19 spreads when an infected person breathes out droplets and very small particles that contain the virus. These droplets and particles can be breathed in by other people or land on their eyes, noses, or mouth. In some circumstances, they may contaminate surfaces they touch.

About Variants

Many viruses are constantly changing, including the virus that causes COVID-19. These changes occur over time and can lead to the emergence of variants that may have new characteristics, including different ways of spreading.

Anyone infected with COVID-19 can spread it, even if they do NOT have symptoms.

Learn more about what you can do to protect yourself and others.

Understanding Exposure Risks:


Factors that lower or increase risk of transmission

Length of time: How long were you with the infected person?

Longer exposure time increases the risk of transmission (for example, contact longer than 15 minutes is more likely to result in transmission than two minutes of contact).

Shorter exposure time                                                   

Lower Risk

Medium exposure time

Moderate Risk

Longer exposure time.

Higher Risk

Cough or heavy breathing: Was the infected person coughing, singing, shouting, or breathing heavily?

Activities like coughing, singing, shouting, or breathing heavily due to exertion increase the risk of transmission.

Lower Risk



Moderate Risk


Higher Risk

Symptoms: Did the infected person have symptoms at the time? i

Being around people who are symptomatic increases the risk of transmission.

No symptoms.

Lower Risk


Higher Risk

Masks: Were you or the infected person or both wearing a respirator (for example, N95) or high-quality mask?

If one person was wearing a mask, the risk of transmission is decreased, and if both people were wearing masks, the risk is substantially decreased. Risk is also lower if the mask or respirator is a type that offers greater protection.

Yes, both masked

Lower Risk

Only one masked.

Moderate Risk

Neither masked.

Higher Risk

Ventilation and filtration: How well-ventilated was the space?

More outdoor air can decrease the risk of transmission. Being outside would be lower exposure risk than being indoors, even with good ventilation and filtration; both of those options would be lower risk than being indoors with poor ventilation or filtration. See the Interactive Home Ventilation Tool.


Lower Risk

Well-ventilated indoors


Moderate Risk

Poorly ventilated indoors.

Higher Risk

Distance: How close was the infected person to you?

Being closer to someone who is infected with COVID-19 increases the risk of transmission. Crowded settings can raise your likelihood of being close to someone with COVID-19.

Lower Risk

Moderately close.

Moderate Risk

Very close or touching shoulder.

The CDC website has additional FAQs on the topics of Travel, Pregnant Women and COVID-19, and COVID-19 and animals.

This page includes information from

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