COVID-19 symptoms

Updated Jan. 24, 2021

UC Davis Health is committed to providing you with the most up-to-date information on COVID-19 symptoms. Learn more about symptoms of COVID-19 and which can be the first indicators of illness:

COVID-19 symptoms may appear 2-14 days after exposure to the virus, according to the Center for Disease Control and Prevention (CDC). People with one or many of these symptoms in any combinations may have COVID-19:

  • fever or chills
  • dry coughs
  • shortness of breath associated with respiratory illness
  • fatigue
  • muscle pain or body ache
  • headache
  • new loss of taste or smell
  • sore throat
  • congestion or runny nose
  • diarrhea
  • nausea or vomiting

While typical of COVID-19, these all may be symptoms of some other illness, too. Call your primary care provider if you have symptoms and believe you were in close contact with an infected person. You can also speak with a physician using Express Care or MyUCDavisHealth.

All of the variants, including omicron, cause similar symptoms, including cough, fever and fatigue. There is some evidence that fewer people with omicron are experiencing a loss of taste and smell. Omicron is also less likely to cause severe disease such as pneumonia that may require treatment in the hospital.

In fully vaccinated and/or boosted people, symptoms tend to be mild. In unvaccinated people, symptoms may be quite severe, possibly leading to hospitalization or even death.

Learn more about the omicron variant from UC Davis Health 

Most people who test positive for COVID-19 typically experience symptoms for a couple weeks. People who have long-haul COVID-19 symptoms, also called "long COVID," can experience health problems for four or more weeks after first being infected, according to the CDC.

The CDC says you should watch for these more sever symptoms, in which you should seek emergency medical attention:

  • trouble breathing
  • persistent pain or pressure in the chest
  • new confusion
  • inability to wake up or stay awake
  • pale, gray, or blue-colored skin, lips, or nail beds, depending on skin tone

**This is not a list of all possible severe symptoms. Call your health care provider for any symptoms that are concerning to you.

Most patients with omicron infection will have mild symptoms, especially those who are vaccinated with breakthrough infections. These patients may experience fever, cough, sore throat, fatigue, muscle pain and headache without progression to pneumonia.

People who are unvaccinated and are infected with omicron are at higher risk for the infection progressing to moderate or severe illness. This may result in pneumonia, difficulty breathing, and the need to be hospitalized for supplemental oxygen.

Typically, vaccinated people who test positive for COVID-19 are either asymptomatic or have very mild symptoms. It rarely results in hospitalization or death. Their symptoms are more like those of a common cold, such as cough, fever or headache, with the addition of significant loss of smell.

No vaccine is 100% effective. Health experts continue to see that the risk of infection, hospitalization, and death are much lower in vaccinated people compared to unvaccinated.

Learn more about the COVID-19 vaccine

The earliest symptoms of COVID-19 will most likely be a fever, followed by a cough and muscle pain, according to a study by the University of Southern California. Next, infected people will possibly experience nausea or vomiting and diarrhea. Initial COVID-19 symptoms are similar to other respiratory illnesses such as MERS and SARS. However, patients with COVID-19 will likely develop nausea and vomiting before diarrhea, which is opposite from MERS and SARS, the USC researchers said.

If someone is showing these symptoms, you should seek emergency medical care immediately:

  • trouble breathing
  • persistent pain or pressure in the chest
  • new confusion
  • inability to wake or stay awake
  • bluish lips or face

This is not a complete list of possibly symptoms. Call your primary care provider for any other symptoms that seem severe or are a concern to you.

Influenza (flu) and COVID-19 are both contagious respiratory illnesses and they have similar symptoms. It may be difficult to tell the difference based on symptoms alone, but there are two key differences, according to the CDC:

  • Those infected with COVID-19 sometimes experience change in or loss of taste and smell, which is less commonly a symptom of the flu.
  • The USC researchers said the flu usually begins with a cough, whereas COVID-19 most often starts with a fever.
  • People infected with flu typically develop symptoms 1-4 days after infection. Those with COVID-19 typically develop symptoms 5 days after being infected. However, people infected with COVID-19 can show symptoms as early as 2 days or as late as 14 days after infection.

Learn about flu prevention and how to schedule your flu vaccine

Upper respiratory allergy symptoms typically include:

  • runny nose
  • itchy eyes
  • sneezing

If these continue after exposure to something that usually triggers an allergy, or during the usual time of year you experience seasonal allergies, then it’s reasonable to attribute these symptoms to allergies rather than infection. But if there are other associated symptoms such as fever or cough – or they happen without the usual allergy exposures – then these could be signs of COVID-19 infection.

Fever and cough are the most common COVID-19 symptoms in children, according to the CDC. "The symptoms of COVID-19 are similar in adults and children and can look like other common illnesses, like colds, strep throat, or allergies," the CDC reports. In addition to the COVID-19 symptoms listed above, children may also experience:

  • stomachache
  • poor appetite
  • poor feeding, especially for babies under 1 year old.

In some children, fever may be the only sign of COVID-19 infection.

Learn more about COVID-19 symptoms in children

Parents should especially watch for the following novel coronavirus symptoms in children:

  • fever (temperature of 100.4°F or higher)
  • sore throat
  • new uncontrolled cough that causes difficulty in breathing
  • diarrhea, vomiting or stomachache
  • new severe headache, especially with fever

Coronavirus symptoms can last weeks or months for some people, known as "long haulers". These people have, in theory, recovered from the worst impacts of COVID-19 and are no longer contagious. However, they still have symptoms. There seems to be no consistent reason for the symptoms to stay around so long.

This condition can effect anyone – old and young, otherwise healthy people and those battling other conditions. It has been seen in those who were hospitalized with COVID-19 and patients with very mild symptoms. However, it appears to be less common in children compared to adults. Additionally, it's less common for those who have breakthrough infections (vaccinated people) to get the virus vs. unvaccinated people.

Learn more about COVID-19 long haulers

COVID-19 infection can cause inflammation and damage to the heart muscle and inflammation to the covering of the heart. According to the CDC, this heart damage can explain why some people have reported long-term symptoms like:

  • shortness of breath
  • chest pain
  • heart palpitations

Those infected with COVID-19 can also experience lasting lung problems. Prolonged illness and continued symptoms can occur even in young adults without chronic medical conditions. This could lead to an extended absence from work, studies, or other activities. Researchers are still investigating what other short- and long-term health effects are associated with COVID-19.