COVID-19 is a disease caused by a virus called SARS-CoV-2. Most people with COVID-19 have mild symptoms, but some people can become severely ill. Although most people with COVID-19 get better within weeks of illness, some people experience post-COVID conditions. Post-COVID conditions are a wide range of new, returning, or ongoing health problems people can experience more than four weeks after first being infected with the virus that causes COVID-19. Older people and those who have certain underlying medical conditions are more likely to get severely ill from COVID-19. Vaccines against COVID-19 are safe and effective.

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. People who are closer than 6 feet from the infected person are most likely to get infected.

COVID-19 is spread in three main ways:

• Breathing in air when close to an infected person who is exhaling small droplets and particles that contain the virus.
• Having these small droplets and particles that contain virus land on the eyes, nose, or mouth, especially through splashes and sprays like a cough or sneeze.
• Touching eyes, nose, or mouth with hands that have the virus on them.

For more information about how COVID-19 spreads, visit the How COVID-19 Spreads page to learn how COVID-19 spreads and how to protect yourself. 

Visit the How to Protect Yourself & Others page to learn about how to protect yourself from respiratory illnesses, like COVID-19.

People who have been in close contact with someone who has COVID-19—excluding people who have had COVID-19 within the past 3 months or who are fully vaccinated

• People who have tested positive for COVID-19 within the past 3 months and recovered do not have to quarantine or get tested again as long as they do not develop new symptoms.
• People who develop symptoms again within 3 months of their first bout of COVID-19 may need to be tested again if there is no other cause identified for their symptoms.
• People who have been in close contact with someone who has COVID-19 are not required to quarantine if they have been fully vaccinated against the disease and show no symptoms.

For more information, see COVID-19: When to Quarantine and What to Do If You Are Sick.

• Isolation separates someone who is infected with the virus that causes COVID-19 (or presumed to be infected because they have symptoms) away from people who are not infected, including house members.
• Quarantine separated people who were exposed to the virus that causes COVID-19 from others, including household members, during the time when they could become sick and infect others.

Look for emergency warning signs* for COVID-19. If someone is showing any of these signs, seek emergency medical care immediately

• Trouble breathing
• Persistent pain or pressure in the chest
• New confusion
• Inability to wake or stay awake
• Pale, gray, or blue-colored skin, lips, or nail beds, depending on skin tone

*This list is not all possible symptoms. Please call your medical provider for any other symptoms that are severe or concerning to you.

The virus that causes COVID-19 is constantly changing, and new variants of the virus are expected to occur. Sometimes new variants emerge and disappear. Other times, new variants persist. Numerous variants of the virus that causes COVID-19 are being tracked in the United States and globally during this pandemic.

If you think about a virus like a tree growing and branching out; each branch on the tree is slightly different than the others. By comparing the branches, scientists can label them according to the differences. These small differences, or variants, have been studied and identified since the beginning of the pandemic.

Some variations allow the virus to spread more easily or make it resistant to treatments or vaccines. Those variants must be monitored more carefully.

As the virus spreads, it has new opportunities to change and may become more difficult to stop. These changes can be monitored by comparing differences in physical traits (such as resistance to treatment) or changes in genetic code (mutations) from one variant to another.

By studying each variant and understanding these differences, scientists can monitor, and often predict, whether a variant is more dangerous than others. Scientists can also use this information to track the spread of a variant.

Omicron – B.1.1.529

First identified: South Africa

Spread: May spread more easily than other variants, including Delta.

Severe illness and death: Due to the small number of cases, the current severity of illness and death associated with this variant is unclear.

Vaccine: Breakthrough infections in people who are fully vaccinated are expected, but vaccines are effective at preventing severe illness, hospitalizations, and death. Early evidence suggests that fully vaccinated people who become infected with the Omicron variant can spread the virus to others. All FDA-approved or authorized vaccines are expected to be effective against severe illness, hospitalizations, and deaths.  The recent emergence of the Omicron variant further emphasizes the importance of vaccination and boosters.

Treatments: Some monoclonal antibody treatments may not be as effective against infection with Omicron.

Delta – B.1.617.2

First identified: India

Spread: Spreads more easily than other variants.

Severe illness and death: May cause more severe cases than the other variants

Vaccine: Breakthrough infections in people who are fully vaccinated are expected, but vaccines are effective at preventing severe illness, hospitalizations, and death. Early evidence suggests that fully vaccinated people who become infected with the Delta variant can spread the virus to others. All FDA-approved or authorized vaccines are effective against severe illness, hospitalization, and death.

Treatments: Nearly all variants circulating in the United States respond to treatment with FDA-authorized monoclonal antibody treatments.

The Delta variant causes more infections and spreads faster than early forms of SARS-CoV-2, the virus that causes COVID-19

• The Delta variant is more contagious: The Delta variant is highly contagious, more than 2x as contagious as previous variants.
• Some data suggest the Delta variant might cause more severe illness than previous variants in unvaccinated people. In two different studies from Canada and Scotland, patients infected with the Delta variant were more likely to be hospitalized than patients infected with Alpha or the original virus that causes COVID-19. Even so, the vast majority of hospitalization and death caused by COVID-19 are in unvaccinated people.
• Unvaccinated people remain the greatest concern: The greatest risk of transmission is among unvaccinated people who are much more likely to get infected, and therefore transmit the virus. Fully vaccinated people get COVID-19 (known as breakthrough infections) less often than unvaccinated people. People infected with the Delta variant, including fully vaccinated people with symptomatic breakthrough infections, can transmit the virus to others. CDC is continuing to assess data on whether fully vaccinated people with asymptomatic breakthrough infections can transmit the virus.
• Fully vaccinated people with Delta variant breakthrough infections can spread the virus to others. However, vaccinated people appear to spread the virus for a shorter time: For prior variants, lower amounts of viral genetic material were found in samples taken from fully vaccinated people who had breakthrough infections than from unvaccinated people with COVID-19. For people infected with the Delta variant, similar amounts of viral genetic material have been found among both unvaccinated and fully vaccinated people. However, like prior variants, the amount of viral genetic material may go down faster in fully vaccinated people when compared to unvaccinated people. This means fully vaccinated people will likely spread the virus for less time than unvaccinated people.

Read more: Here

The Omicron Variant of Concern has been detected in the United States. CDC is following the details of this new variant. CDC’s Media Statement