COVID-19 is caused by the SARS-CoV-2 virus. COVID-19 can cause mild to severe respiratory illness, including death. The best preventive measures include getting vaccinated, wearing a mask during times of high transmission, staying 6 feet apart, washing hands often and avoiding sick people.
Coronaviruses are a family of viruses that can cause respiratory illness in humans. They are called “corona” because of crown-like spikes on the surface of the virus. Severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS) and the common cold are examples of coronaviruses that cause illness in humans.
The new strain of coronavirus — SARS-CoV-2 — was first reported in Wuhan, China in December 2019. It has since spread to every country around the world.
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Coronaviruses are often found in bats, cats and camels. The viruses live in but don’t infect the animals. Sometimes these viruses then spread to different animal species. The viruses may change (mutate) as they transfer to other species. Eventually, the virus can jump from animal species and begin to infect humans. In the case of SARS-CoV-19, the first people infected are thought to have contracted the virus at a food market that sold meat, fish and live animals.
SARS-CoV-2, the virus that causes COVID-19, enters your body through your mouth, nose or eyes (directly from the airborne droplets or from the transfer of the virus from your hands to your face). It then travels to the back of your nasal passages and mucous membrane in the back of your throat. It attaches to cells there, begins to multiply and moves into lung tissue. From there, the virus can spread to other body tissues.
Coronavirus is likely spread:
If you have COVID-19 it can take several days to develop symptoms — but you’re contagious during this time. You are no longer contagious 10 days after your symptoms began.
The best way to avoid spreading COVID-19 to others is to:
Persons at greatest risk of contracting COVID-19 include those who:
The time between becoming infected and showing symptoms (incubation period) can range from two to 14 days. The average time before experiencing symptoms is five days. Symptoms can range in severity from very mild to severe. In about 80% of people, COVID-19 causes only mild symptoms, although this may change as variants emerge.
If you test positive for SARS-CoV-2 three months after your last positive test, it’s considered a reinfection. Before the omicron variant, reinfection with SARS-CoV-2 was rare but possible.
Omicron (B.1.1.529) was first reported in South Africa in November 2021 and quickly spread around the world. With many mutations, omicron was able to evade immune systems and we had more reinfections than ever before.
As the virus that causes COVID-19 continues to mutate, reinfection remains possible. Vaccination — including a booster dose — is the best protection against severe disease.
COVID-19 symptoms vary from person to person. In fact, some infected people don’t develop any symptoms (asymptomatic). In general, people with COVID-19 report some of the following symptoms:
Additional symptoms are possible.
Symptoms may appear two to 14 days after exposure to the virus. Children have similar, but usually milder, symptoms than adults. Older adults and people who have severe underlying medical conditions are at higher risk of more serious complication from COVID-19.
Call 911 and get immediate medical attention if you have these warning signs:
This list does not include all possible symptoms. Contact your healthcare provider if you’re concerned you may have coronavirus or have any severe symptoms.
COVID-19 is diagnosed with a laboratory test. Your healthcare provider may collect a sample of your saliva or swab your nose or throat to send for testing.
Call your healthcare provider if you:
Your healthcare provider will ask you questions about your symptoms and tell you if you need to be tested for COVID-19.
According to current CDC recommendations, you should self-isolate until you've met both of the following criteria:
While at home, self-isolate within a separate room of your home if possible to limit interaction with other family members. If you can’t stay 100% isolated in a separate room, keep 6 feet away from others and wear a cloth mask, wash your/family members' hands often and frequently disinfect commonly touched surfaces and shared areas.
You don't need to be retested after your period of self-isolation. But every case is unique, so follow your healthcare provider's recommendations for testing.
If you have a weakened immune system or have had a severe case of COVID-19, the CDC's criteria don’t apply to you. You may need to stay home for up to 20 days after your symptoms first appeared. Talk with your healthcare provider about your situation.
You should quarantine for five days if:
After this time, you should wear a well-fitting mask whenever you’re around others for an additional five days. The CDC recommends testing on day five if possible. This quarantine period may vary depending on variant strains and the availability of testing.
Yes, it’s possible. There are several reasons for “false negative” test results — meaning you really do have COVID-19 although the test result says you don’t.
Reasons for a false negative COVID-19 test result include:
If you think you might have COVID-19 even if your test is negative, it’s best to follow the current CDC recommendations. Stay home for 10 days if you think you are sick (“social distancing”). Stay 6 feet away from others (“physical distancing”) and wear a cloth mask. Contact your healthcare provider if your symptoms worsen. Don’t decide on your own if it’s safe for you to be around others. Instead, contact your healthcare provider when your symptoms improve.
Treatments for COVID-19 vary depending on the severity of your symptoms. If you’re not in the hospital or don’t need supplemental oxygen, no specific antiviral or immunotherapy is recommended.
Depending on the severity of your COVID symptoms, you may need:
Yes, it’s possible to get COVID-19 even if you’ve been vaccinated. No vaccines are 100% effective. In fact, breakthrough cases (when someone tests positive more than two weeks after they're fully vaccinated) are expected, especially as the SARS-CoV-2 virus mutates.
The vaccines significantly reduce — but don’t eliminate — your risk of infection. The risk of a severe illness or death from a breakthrough infection is very low.
If you have mild COVID-19 symptoms, you can likely manage your health at home. Follow these tips:
If you have a mild case of COVID-19, you should start to feel better in a few days to a week. If you think your symptoms are getting worse, call your healthcare provider.
The best defense to prevent getting COVID-19 is to get vaccinated. You should also follow the same steps you would take to prevent getting other viruses, such as the common cold or the flu.
Your healthcare provider can answer any questions you have about when you should wear a face mask to help slow the transmission of COVID-19. In general, the CDC recommends wearing a face mask in the following situations:
A note from Cleveland Clinic
We’ve come a long way since the first cases of COVID-19 were confirmed in the United States. We’ve learned a lot about the virus and how to treat people who have it. We’ve also greatly increased our ability for testing. You — our communities — have made tremendous efforts to adapt, too.
The changes we’ve all made to stay safe and healthy can feel challenging. But please stay vigilant. We know it’s not easy, but it’s critical. COVID-19 shouldn't be taken lightly. While most people get only mild symptoms, others develop serious complications of the lungs, brain and heart. There may also be other long-term effects that we don’t yet know about.
Last reviewed by a Cleveland Clinic medical professional on 03/01/2022.
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