People who are asymptomatic show no signs or symptoms of an illness or disease, such as COVID-19, but can still transmit the virus that causes the disease to others. Anyone who has come into contact with someone who tests positive for COVID-19 must get a test themselves.

When a person is asymptomatic, they have a condition, disease, illness, or infection but do not show or develop any signs or symptoms of that condition.

However, when a person is presymptomatic, they have the condition but have not yet got any symptoms but will develop them later on.

People who are asymptomatic and presymptomatic with COVID-19 can transmit SARS-CoV-2, the virus that causes the disease, to others.

Although people can be asymptomatic for many diseases, this article focuses on COVID-19. It explores the different classifications of COVID-19, grouped by severity of symptoms, and looks at how many people develop symptoms, who gets COVID-19, how to identify it, and what to do.

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For more advice on COVID-19 prevention and treatment, visit our coronavirus hub.

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Researchers do not yet fully understand how many people who develop COVID-19 will experience symptoms.

Different studies estimate different rates, with some suggesting that around 30% of people with COVID-19 will never develop symptoms. However, another small study that took place on a cruise ship in 2020 estimated that the figure might be as high as 81%.

However, some of these estimates may have changed since the studies took place and may not consider newer, more virulent strains of the virus, such as the Delta variant.

The World Health Organisation (WHO) states that people typically develop symptoms of COVID-19 about 5-6 days after they contract the virus, but it can take up to 14 days for symptoms to appear. However, if a person has not developed symptoms by this time, it is unlikely that they will.

Learn more about how long it takes for COVID-19 symptoms to develop here.

Asymptomatic people can transmit the virus that causes COVID-19. This is particularly dangerous because if a person does not know that they have the virus, they will likely not isolate. This means that they are more likely to be around others and therefore have a higher risk of passing the virus on to others.

One study suggests that up to 59% of virus transmissions come from people who are asymptomatic, 35% of whom were presymptomatic, and 24% who did not ever have any symptoms.

These figures may be inaccurate now, as the 2021 study took place before the Delta variant became the dominant, more transmissible strain.

Scientists classify COVID-19 in the following ways, depending on the severity of the condition.

They include:

  • asymptomatic
  • mild
  • moderate
  • severe
  • critical

A person may experience more than one classification of COVID-19 if their condition progresses over time.


An asymptomatic person has tested positive for COVID-19 but never exhibits any signs or symptoms of the disease.

However, some people within this category are presymptomatic, which means they have tested positive for the disease and do not yet have any symptoms but develop them later.


If a person has mild COVID-19, they may experience some of the following symptoms.

People with underlying conditions and older people may need monitoring for the progression of the disease to a later and more serious stage.

Younger adults with mild COVID-19 who do not have underlying conditions can usually receive treatment at home through telemedicine or telephone calls with healthcare professionals.


If an assessment by a medical professional shows evidence of lower respiratory disease, along with oxygen saturation of equal to or less than 94%, a person may have moderate COVID-19.


With severe COVID-19, a person will require oxygen therapy.

People with severe COVID-19 may progress rapidly to a critical medical situation, and therefore medical professionals should monitor these people closely.


This is where a person with COVID-19 experiences the symptoms above, along with respiratory failure, multiple organ dysfunction, or septic shock.

This is where a person with COVID-19 experiences the symptoms above, along with respiratory failure, multiple organ dysfunction, or septic shock.

Any underlying conditions may worsen if a person develops critical COVID-19. Healthcare professionals will treat the COVID-19 infection and the person’s underlying conditions.

COVID-19 can affect anyone. However, some groups of people are more likely to develop severe or critical COVID-19.

These include people who:

Additionally, people who are pregnant are at higher risk of developing more severe COVID-19. People who smoke and those who have been recipients of transplants or immunosuppressive therapy may also be at higher risk.

COVID-19 has disproportionately affected many Communities of Color and other marginalized groups.

People from marginalized communities, including People of Color, are more likely to experience severe and critical COVID-19 and more likely to die from the infection. This is due to disparities in social determinants of health.

Learn more about health equity in our dedicated hub.

If a person thinks they may have COVID-19, they should stay home and take a test.

Most people will be able to manage their symptoms at home.

The most common symptoms people experience if they have COVID-19 include:

Less common symptoms include:

  • aches and pains
  • headaches
  • a rash on skin or discoloration of fingers or toes
  • diarrhea
  • sore throat
  • loss of taste or smell

Symptoms that could indicate a serious case include:

  • shortness of breath
  • difficulty breathing
  • chest pain
  • loss of speech or inability to move properly

People who experience more severe symptoms should seek medical attention.

However, anyone who has been in contact with someone with COVID-19 but does not have symptoms should take a test to check whether they have contracted the virus.

If a person who has not had a COVID-19 vaccination comes into contact with someone with COVID-19, they need to quarantine and take a test on the 5th day after exposure if they do not have symptoms.

Quarantine is when a person restricts their movement and interaction with others because they may have contracted a disease or had exposure to someone with the disease to see if they develop it.

A person who has had a COVID-19 vaccination may not need to quarantine to the same extent, but they should reduce their interactions with other people and take a test after 3-5 days. People who have had a vaccination and have no symptoms can still transmit the virus infection to others.

Anyone with symptoms should isolate and, ideally, take a test 3 days after symptoms develop. Isolation is when someone who has a disease separates themselves from others to prevent transmitting it.

Avoid taking a test before these recommended times, as it may result in a false negative. This is because it takes a few days for the virus to build up and register on the test.

Learn about the differences between quarantine and isolation.

People with COVID-19 should seek advice from their local health authorities on what actions to take and follow the appropriate guidelines.

Anyone with COVID-19 should advise the people they have been in contact with that they have tested positive, so they can also get a test.

The only time a person with COVID-19 should leave their home is to seek medical care if their doctor has advised them to do so.

According to the WHO, anyone experiencing symptoms of COVID-19, including fever, cough, or difficulty breathing, should seek medical attention as soon as possible.

However, they should seek medical consultation by phone and follow the local recommendations to help prevent the spread of COVID-19 in the local area.

Asymptomatic means that people experience a condition without developing any of the symptoms associated with it.

SARS-CoV-2 can still transmit from asymptomatic people despite them showing no symptoms. Therefore, anyone with a positive SARS-CoV-2 test must isolate and carry out appropriate measures to prevent the condition from spreading to others.

For live updates on the latest developments regarding the novel coronavirus and COVID-19, click here.