What's the concern about COVID-19 variants? Are they more contagious?

Concern over variants, sometimes called strains, of the virus that causes COVID-19 is based on how the virus might change. A virus could get better at infecting people, spread faster or cause people to get sicker.

As a virus infects a group of people, the virus copies itself. During this process the genetic code can randomly change in each copy. These changes are called mutations.

Some mutations don't have any effect on the virus.

But other mutations can:

  • Make the virus better at infecting a person's cells, causing serious illness.
  • Make the virus better at avoiding the immune system.
  • Cause tests for the virus to be less accurate.
  • Cause vaccines to not work as well.
  • Make medicine used to prevent or treat COVID-19 stop working or not work as well.

If a mutation changes how a virus acts in a group of people, it's called a variant. Scientists across the world track the changes in the virus variants that cause COVID-19.

Omicron

The main variant in the United States is omicron. This variant spreads more easily than the original virus that causes COVID-19 and the delta variant. But omicron seems to cause less severe disease.

Omicron has a few major offshoots, also called sublineages. Together the omicron variants make up nearly all COVID-19 infections in the United States.

People who are up to date on their vaccines can get breakthrough infections. They can then spread the virus to others. But the COVID-19 vaccines can work to prevent severe illness. To strengthen your protection against the virus that causes COVID-19, the CDC recommends staying up to date with COVID-19 vaccines for which you are eligible.

History of infectious disease outbreaks and vaccines timeline.

Learn about the history of major disease outbreaks, epidemics and pandemics, as well as the impact vaccines and research had on many infectious diseases.

Find out more at History of infectious disease outbreaks and vaccines timeline.

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

We use the data you provide to deliver you the content you requested. To provide you with the most relevant and helpful information, we may combine your email and website data with other information we have about you. If you are a Mayo Clinic patient, we will only use your protected health information as outlined in our Notice of Privacy Practices. You may opt out of email communications at any time by clicking on the unsubscribe link in the email.

June 21, 2024 See more Expert Answers

See also

  1. Antibiotics: Are you misusing them?
  2. Convalescent plasma therapy
  3. Coronavirus disease 2019 (COVID-19)
  4. Coronavirus infection by race
  5. COVID-19 and pets
  6. COVID-19 and vitamin D
  7. COVID-19 and your mental health
  8. COVID-19 antibody testing
  9. COVID-19 drugs: Are there any that work?
  10. COVID-19 in babies and children
  11. COVID-19 tests
  12. COVID-19 travel advice
  13. COVID-19 vaccine: Should I reschedule my mammogram?
  14. COVID-19 vaccines
  15. COVID-19 vaccines for kids: What you need to know
  16. COVID-19 vs. flu: Similarities and differences
  17. COVID-19, cold, allergies and the flu
  18. COVID-19: How can I protect myself?
  19. COVID-19: Who's at higher risk of serious symptoms?
  20. Debunking coronavirus myths
  21. Diarrhea
  22. Different COVID-19 vaccines
  23. Extracorporeal membrane oxygenation (ECMO)
  24. Fever
  25. Fever treatment: Quick guide to treating a fever
  26. Fever: First aid
  27. Fight coronavirus (COVID-19) transmission at home
  28. Herd immunity and coronavirus
  29. Honey: An effective cough remedy?
  30. How do COVID-19 antibody tests differ from diagnostic tests?
  31. How to measure your respiratory rate
  32. How to take your pulse
  33. How to take your temperature
  34. How well do face masks protect against COVID-19?
  35. Is hydroxychloroquine a treatment for COVID-19?
  36. Long-term effects of COVID-19
  37. Mayo Clinic Minute: How dirty are common surfaces?
  38. Mayo Clinic Minute: You're washing your hands all wrong
  39. Multisystem inflammatory syndrome in children (MIS-C)
  40. Pregnancy and COVID-19
  41. Safe outdoor activities during the COVID-19 pandemic
  42. Safety tips for attending school during COVID-19
  43. Sex and COVID-19
  44. Stool color: When to worry
  45. Thermometers: Understand the options
  46. Thrombocytopenia
  47. Treating COVID-19 at home
  48. Undigested food in stool
  49. Unusual symptoms of coronavirus