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If you've been exposed to the coronavirus

April 12, 2022

If you've been exposed, are sick, or are caring for someone with COVID-19

Woman taking care of sick relative

If you've been exposed to someone with COVID-19 or begin to experience symptoms of the disease, you may be asked to self-quarantine or self-isolate. What does that entail, and what can you do to prepare yourself for an extended stay at home? How soon after you're infected will you start to be contagious? And what can you do to prevent others in your household from getting sick?

Visit our Coronavirus Resource Center for more information on coronavirus and COVID-19.

Jump to: Symptoms | Testing | Antibodies | Contagiousness | Long Term Effects

Symptoms of COVID-19

What are the symptoms of COVID-19?

Some people infected with the virus have no symptoms. When the virus does cause symptoms, common ones include fever, body ache, dry cough, fatigue, chills, headache, sore throat, loss of appetite, and loss of smell. In some people, COVID-19 causes more severe symptoms like high fever, severe cough, and shortness of breath, which often indicates pneumonia.

People with COVID-19 can also experience neurological symptoms, gastrointestinal (GI) symptoms, or both. These may occur with or without respiratory symptoms.

For example, COVID-19 affects brain function in some people. Specific neurological symptoms seen in people with COVID-19 include loss of smell, inability to taste, muscle weakness, tingling or numbness in the hands and feet, dizziness, confusion, delirium, seizures, and stroke.

In addition, some people have gastrointestinal (GI) symptoms, such as loss of appetite, nausea, vomiting, diarrhea, and abdominal pain or discomfort associated with COVID-19.

What should I do if I think I or my child may have a COVID-19 infection?

First, call your doctor or pediatrician for advice.

If you do not have a doctor and you are concerned that you or your child may have COVID-19, contact your local board of health. They can direct you to the best place for testing and treatment in your area. Over-the-counter tests may also be available at your local pharmacy or grocery store.

If you do test positive and either have no symptoms or can recover at home, you will still need to

  • isolate at home for five days
  • if you have no symptoms or your symptoms are improving after five days, you can discontinue isolation and leave your home
  • continue to wear a mask around others for five additional days.

If you have a fever, continue to isolate at home until you no longer have a fever.

If you have a high or very low body temperature, shortness of breath, confusion, or feeling you might pass out, you need to seek immediate medical evaluation. Call the urgent care center or emergency department ahead of time to let the staff know that you are coming, so they can be prepared for your arrival.

What is "Test to Treat"? Could it help me get antiviral treatment for COVID-19?

Test to Treat is a government initiative that makes it faster and easier for people with COVID-19 to obtain treatment. This is important because antiviral treatments for COVID-19 must be started within five days of a positive test or the start of symptoms. With Test to Treat, a person can get tested, get a prescription, and get their prescription filled, all in one place.

Here’s how it works. If you think you may have COVID-19, go to a Test to Treat site to get tested. If you test positive you will meet with a healthcare provider and, if you are eligible, will receive a prescription for antiviral treatment. You can then get your prescription filled at the same site.

A few things to keep in mind:

  • You can bring a positive at-home test to a Test to Treat site.
  • A healthcare provider at the Test to Treat site may ask about your medical history or other medications you take in order to make sure you are eligible for treatment.
  • The two antiviral treatments being prescribed and filled at Test to Treat sites are Paxlovid and molnupiravir (Lagevrio).

The Test to Treat web-based locator can help you find a Test to Treat site near you. You can also call 800-232-0233 to get help in English, Spanish, and more than 150 other languages.

How do I know if I have COVID-19, the flu, or just a cold?

Now that the Omicron variant of COVID-19 is the dominant strain, telling the difference is more challenging than ever. Even if you have been vaccinated and boosted, you can still get symptoms, but they are likely to be mild to moderate in severity. For those not vaccinated, the risk of severe symptoms that can be life-threatening is still substantial.

At the current time, people with "flulike" symptoms should assume they have COVID. If possible, arrange to get tested or do a home test. If the test is positive, you should isolate at home for five days. If you had a negative test when symptoms started, it’s still best to isolate at home for two to three more days, to monitor your symptoms and prevent spreading infection. (That’s because there is a chance of false negatives with antigen tests, which means you can still have COVID with a negative test.) Consider testing again before going out. Once you are ready to leave home, continue to consistently wear a mask for at least five more days.

COVID-19 Testing

I recently spent time with someone who tested positive for COVID-19. I’m fully vaccinated and boosted. Do I need to get tested?

According to the latest CDC guidelines, if you are vaccinated and boosted, or have gotten your initial vaccine series within the last six months (for Pfizer/BioNTech or Moderna) or the last two months (for Johnson & Johnson), you should wear a mask around others for 10 days and take a COVID test on day 5, if possible. If you develop symptoms, get tested sooner and isolate at home.

If you are unvaccinated, had your last Pfizer or Moderna shot more than six months ago and have not been boosted, or had your Johnson & Johnson shot more than two months ago and have not been boosted, you should stay home for five days and wear a mask around others for an additional five days. If you can't quarantine, wear a mask around others for 10 days. Get tested for COVID on day 5, if possible. If you develop symptoms at any time, get tested and isolate at home.

What is the difference between a PCR test and an antigen test for COVID-19?

PCR tests and antigen tests are both diagnostic tests, which means that they can be used to determine whether you currently have an active coronavirus infection. However, there are important differences between these two types of tests.

PCR tests detect the presence of the virus's genetic material using a technique called reverse transcriptase polymerase chain reaction, or RT-PCR. For this test, a sample may be collected through a nasal or throat swab, or a saliva sample may be used. The sample is typically sent to a laboratory where coronavirus RNA (if present) is extracted from the sample and converted into DNA. The DNA is then amplified, meaning that many copies of the viral DNA are made, in order to produce a measurable result. The accuracy of any diagnostic test depends on many factors, including whether the sample was collected properly, when during the course of illness the testing was done, and whether the sample was maintained in appropriate conditions while it was shipped to the laboratory. Generally speaking, PCR tests are highly accurate.

Antigen tests detect specific proteins on the surface of the coronavirus. They are sometimes referred to as rapid diagnostic tests because it can take less than an hour to get the test results. Positive antigen test results are highly specific, meaning that if you test positive you are very likely to be infected. However, there is a higher chance of false negatives with antigen tests, which means that a negative result cannot definitively rule out an active infection. If you have a negative result on an antigen test, your doctor may order a PCR test or a second rapid antigen test to confirm the result.

It may be helpful to think of a COVID antigen test as you would think of a rapid strep test or a rapid flu test. A positive result for any of these tests is likely to be accurate, and allows diagnosis and treatment to begin quickly, while a negative result often results in further testing to confirm or overturn the initial result.

How reliable are the tests for COVID-19?

Two types of diagnostic tests are currently available in the US. PCR tests detect viral RNA. Antigen tests, also called rapid diagnostic tests, detect specific proteins on the surface of the coronavirus. Antigen test results may come back in as little as 15 to 45 minutes; you may wait several days for PCR test results.

The accuracy of any diagnostic test depends on many factors, including whether the sample was collected properly. For PCR tests, which are typically analyzed in a laboratory, test results may be affected by the conditions in which the test was shipped to the laboratory.

Results may also be affected by the timing of the test. For example, if you are tested on the day you were infected, your test result is almost guaranteed to come back negative, because there are not yet enough viral particles in your nose or saliva to detect. The chance of getting a false negative test result decreases if you are tested a few days after you were infected, or a few days after you develop symptoms.

Generally speaking, if a test result comes back positive, it is almost certain that the person is infected.

A negative test result is less definite. There is a higher chance of false negatives with antigen tests, and early data suggests that antigen tests may be even more likely to miss the Omicron variant. If you have a negative result on an antigen test, your doctor may order a PCR test or recommend a second rapid antigen test to confirm the result.

If you experience COVID-like symptoms and get a negative PCR test result, there is no reason to repeat the test unless your symptoms get worse. If your symptoms do worsen, call your doctor or local or state healthcare department for guidance on further testing. You should also self-isolate at home. Wear a mask when interacting with members of your household. And practice physical distancing.

What is serologic (antibody) testing for COVID-19? What can it be used for?

A serologic test is a blood test that looks for antibodies to SARS-CoV-2 created by your immune system in response to infection or vaccination.

Your body takes one to three weeks after you have acquired the infection to develop antibodies to this virus. For this reason, serologic tests are not sensitive enough to accurately diagnose an active COVID-19 infection, even in people with symptoms.

Antibodies and Spreading COVID-19

I've heard that the immune system produces different types of antibodies when a person is infected with the COVID-19 coronavirus. How do they differ? Why is this important?

When a person gets or is vaccinated against a viral or bacterial infection, a healthy immune system makes antibodies against one or more components of the virus or bacterium.

The COVID-19 coronavirus contains ribonucleic acid (RNA) surrounded by a protective layer, which has spike proteins on the outer surface that can latch on to certain human cells. Once inside the cells, the viral RNA starts to replicate and also turns on the production of proteins, both of which allow the virus to infect more cells and spread throughout the body, especially to the lungs.

While the immune system could potentially respond to different parts of the virus, it's the spike proteins that get the most attention. Immune cells recognize the spike proteins as a foreign substance and begin producing antibodies in response.

There are two main categories of antibodies:

Binding antibodies. These antibodies can bind to either the spike protein or a different protein known as the nucleocapsid protein. Binding antibodies can be detected with blood tests starting about one week after the initial infection. If antibodies are found, it's extremely likely that the person has been infected with the COVID-19 coronavirus. The antibody level declines over time after an infection, sometimes to an undetectable level.

Binding antibodies help fight the infection, but they might not offer protection against getting reinfected in the future. It depends on whether they are also neutralizing antibodies.

Neutralizing antibodies. The body makes neutralizing antibodies that attack the coronavirus's spike protein, making it more difficult for the virus to attach to and enter human cells. Neutralizing antibodies provide more lasting protection than binding antibodies against reinfection.

Monoclonal antibodies are manmade versions of neutralizing antibodies. The FDA has authorized monoclonal antibody treatments for certain groups of COVID-19 patients.

Can a person who has been infected with coronavirus get infected again?

The immune system responds to COVID-19 infection by stimulating white blood cells called lymphocytes to form antibodies that fight the infection. These antibodies and lymphocytes retain a temporary protective effect against reinfection. But it is only temporary. There have been many confirmed cases of reinfection with COVID-19. In other words, a person got sick with COVID-19, recovered, and then became infected again.

This has been especially true as the coronavirus has mutated into COVID-19 variants. There was a rise in reinfections with the Delta variant, and an explosive increase in the reinfection rate due to the Omicron variant. Omicron has about 50 mutations, including more than 30 mutations on the spike protein, the region of the virus that our immune systems recognize after previous infection. Because of this, Omicron is more capable than previous variants of evading our immune defenses and causing reinfection.

We have learned that vaccination plus a booster dose strengthens the natural immune response, even in those who have been previously infected, and further reduces the risk of reinfection. Although breakthrough infections after vaccination are also more common with Omicron than previous variants, vaccination continues to protect well against severe illness.

The bottom line? Get vaccinated and boosted whether or not you’ve already had COVID-19.

Contagiousness of COVID-19

How soon after I'm infected with the new coronavirus will I start to be contagious?

The time from exposure to symptom onset (known as the incubation period) is thought to be two to 14 days. Symptoms typically appeared within five days for early variants, and within four days for the Delta variant. The incubation period appears to be even shorter – about three days – for the Omicron variant.

We know that people tend to be most infectious early in the course of their infection. With Omicron, most transmission occurs during the one to two days before onset of symptoms, and in the two to three days afterwards.

Wearing masks, particularly indoors, can help reduce the risk that someone who is infected but not yet experiencing symptoms may unknowingly infect others.

Can people without symptoms spread the virus to others?

"Without symptoms" can refer to two groups of people: those who eventually do have symptoms (pre-symptomatic) and those who never go on to have symptoms (asymptomatic). During this pandemic, we have seen that people without symptoms can spread the coronavirus infection to others.

A person with COVID-19 may be contagious 48 hours before starting to experience symptoms. In fact, people without symptoms may be more likely to spread the illness, because they are unlikely to be isolating and may not adopt behaviors designed to prevent spread.

But what about people who never go on to develop symptoms? A study published in JAMA Network Open found that almost one out of every four infections may be transmitted by individuals with asymptomatic infections. The proportion of asymptomatic transmission appears to be even higher with the Omicron variant.

Getting vaccinated and boosted once you are eligible is important for protecting not just yourself but others as well; evidence suggests that you're less likely to infect others, or may be contagious for a shorter period of time, once you've been vaccinated.

For how long after I am infected will I continue to be contagious? How long do I need to isolate?

People are thought to be most contagious early in the course of their illness. With Omicron, most transmission appears to occur during the one to two days before onset of symptoms, and in the two to three days afterwards. People with no symptoms can also spread the coronavirus to others.

By the 10th day after COVID symptoms begin, most people will no longer be contagious, as long as their symptoms have continued to improve and their fever has resolved. People who test positive for the virus but never develop symptoms over the following 10 days after testing are also probably no longer contagious.

According to the CDC’s isolation guidelines, everyone who tests positive for COVID-19 should

  • isolate at home for five days
  • if you have no symptoms or your symptoms are improving after five days, you can discontinue isolation and leave your home
  • continue to wear a mask around others for five additional days.

If you have a fever, continue to isolate at home until you no longer have a fever.

You can use the CDC’s Quarantine and Isolation calculator to help determine when and how long you should stay home, get tested, and wear a mask around others if you have COVID-19 or were recently in close contact with someone who tested positive for COVID-19.

I’m vaccinated but got a breakthrough COVID infection. Can I still spread the infection to others?

Yes, you can. That's why the CDC recommends that everyone who tests positive for COVID-19 should isolate from others for at least five days, regardless of their vaccination status.

How can I protect myself while caring for someone that may have COVID-19?

You should take many of the same precautions as you would if you were caring for someone with the flu:

  • Stay in another room or be separated from the person as much as possible. Use a separate bedroom and bathroom, if available.
  • Make sure that shared spaces in the home have good air flow. If possible, open a window.
  • Wash your hands often with soap and water for at least 20 seconds or use an alcohol-based hand sanitizer that contains 60 to 95% alcohol, covering all surfaces of your hands and rubbing them together until they feel dry. Use soap and water if your hands are visibly dirty.
  • Avoid touching your eyes, nose, and mouth with unwashed hands.
  • You and the person should wear a face mask if you are in the same room.
  • Wear a disposable face mask and gloves when you touch or have contact with the person's blood, stool, or body fluids, such as saliva, sputum, nasal mucus, vomit, urine.
    • Throw out disposable face masks and gloves after using them. Do not reuse.
    • First remove and throw away gloves. Then, immediately clean your hands with soap and water or alcohol-based hand sanitizer. Next, remove and throw away the face mask, and immediately clean your hands again with soap and water or alcohol-based hand sanitizer.
  • Do not share household items such as dishes, drinking glasses, cups, eating utensils, towels, bedding, or other items with the person who is sick. After the person uses these items, wash them thoroughly.
  • Clean all "high-touch" surfaces, such as counters, tabletops, doorknobs, bathroom fixtures, toilets, phones, keyboards, tablets, and bedside tables, every day. Also, clean any surfaces that may have blood, stool, or body fluids on them. Use a household cleaning spray or wipe.
    • Wash laundry thoroughly.
    • Immediately remove and wash clothes or bedding that have blood, stool, or body fluids on them.
  • Wear disposable gloves while handling soiled items and keep soiled items away from your body. Clean your hands immediately after removing your gloves.
  • Place all used disposable gloves, face masks, and other contaminated items in a lined container before disposing of them with other household waste. Clean your hands (with soap and water or an alcohol-based hand sanitizer) immediately after handling these items.

Can people infect pets with the COVID-19 virus?

The virus that causes COVID-19 does appear to spread from people to pets, according to the FDA, though this is uncommon. Research has found that cats and ferrets are more likely to become infected than dogs.

If you become sick with COVID-19, it’s best to restrict contact with your pets, just like you would around other people. This means you should forgo petting, snuggling, being kissed or licked, and sharing food or bedding with your pet until you are feeling better. When possible, have another member of your household care for your pets while you are sick. If you must care for your pet while you are sick, wash your hands before and after you interact with your pets and wear a face mask.

At present, it is considered unlikely that pets can spread the COVID-19 virus to humans. However, pets can spread other infections that cause illness, including E. coli and Salmonella, so wash your hands thoroughly with soap and water after interacting with your animal companions.

Long Term Effects of COVID-19

I had COVID-19 a few months ago. Am I at increased risk for health problems in the future?

It does appear that people who recover from COVID-19 have an increased risk of developing other medical conditions, at least in the short term.

One study, published in The BMJ, collected laboratory test and hospital admissions data from a health plan in the US. The researchers compared data from more than 190,000 adults, ages 18 to 65 years, who tested positive for the SARS-CoV-2 virus in 2020, to data from a control group that was collected in 2019, before the pandemic. The researchers followed the participants for six months after they tested positive for SARS-CoV-2 and recorded any new health complications.

They found that 14% of people who had had COVID-19 developed a new medical issue during the following six months; this was nearly 5% higher than the pre-pandemic control group, a significant difference. New medical problems affected a range of body systems and included respiratory failure, abnormal heart rhythms, diabetes, neurological problems, and liver and kidney problems. Increased risk was seen in younger, previously healthy people, but was higher in older people and those with pre-existing medical problems.

Another study, published in Nature, compared the health records of more than 73,000 users of the Veteran’s Health Administration (VHA) who tested positive for SARS-CoV-2 but were never hospitalized, to those of nearly five million other VHA users who never tested positive for COVID-19 and were never hospitalized. For six months following the first 30 days after infection, people who had had COVID-19 were significantly more likely to die or to experience a medical or mental health problem that they had never had before.

These studies provide yet another reason to get vaccinated and boosted if you are eligible.

Who are long-haulers? And what is post-viral syndrome?

Long haulers are people who have not fully recovered from COVID-19 weeks or even months after first experiencing symptoms. Some long haulers experience continuous symptoms for weeks or months, while others feel better for weeks, then relapse with old or new symptoms. The constellation of symptoms long haulers experience, sometimes called post-COVID-19 syndrome or post-acute sequelae of SARS-CoV-2 infection (PASC), is not unique to this infection. Other infections, such as Lyme disease, can cause similar long-lasting symptoms.

Emerging research may help predict who will become a long hauler. One study found that COVID-19 patients who experienced more than five symptoms during their first week of illness were significantly more likely to become long haulers. Certain symptoms — fatigue, headache, difficulty breathing, a hoarse voice, and muscle or body aches — experienced alone or in combination during the first week of illness also increased the chances of becoming a long hauler, as did increasing age and higher body mass index (BMI).

Though these factors may increase the likelihood of long-term symptoms, anyone can become a long hauler. Many long haulers initially have mild to moderate symptoms — or no symptoms at all — and do not require hospitalization. Previously healthy young adults, not just older adults with coexisting medical conditions, are also experiencing post-COVID-19 syndrome.

Symptoms of post-COVID-19 syndrome, like symptoms of COVID-19 itself, can vary widely. Some of the more common lasting symptoms include fatigue, worsening of symptoms after physical or mental activity, brain fog, shortness of breath, chills, body ache, headache, joint pain, chest pain, cough, and lingering loss of taste or smell. Many long haulers report cognitive dysfunction or memory loss that affects their day-to-day ability to do things like make decisions, have conversations, follow instructions, and drive. The common thread is that long haulers haven't returned to their pre-COVID health, and ongoing symptoms are negatively affecting their quality of life. A systematic review published in JAMA Network Open reported that more than half of people infected with COVID-19 continued to experience at least one symptom six months after their diagnosis.

There's already some speculation, but no definite answers, about what is causing these ongoing symptoms. Some researchers suspect that SARS-CoV-2 infection triggers long-lasting changes in the immune system. Others propose that it triggers autonomic nervous system dysregulation, which can impact heart rate, blood pressure, and sweating, among other things.

Blog posts:


You think you've got COVID-19. Here's what you need to do (recorded 4/10/20)

We asked Dr. Mallika Marshall, medical reporter for CBS-affiliate WBZ TV in Boston and an instructor at Harvard Medical School, how we should react when we start to experience a dry cough or perhaps spike a fever. Who do you call? How do you protect your family? When does it make sense to move toward an emergency department, and how should we prepare? Dr. Marshall is the host of Harvard Health Publishing's online course series, and an urgent care physician at Mass General Hospital.

Visit our Coronavirus Resource Center for more information on coronavirus and COVID-19.

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As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.

No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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