The SARS-CoV-2 infection that causes COVID-19 can be contagious for around 2 weeks, but the exact duration varies from person to person. People with the infection can infect others before they develop symptoms, even if they experience no symptoms at all.

The novel coronavirus is highly contagious. It spreads through tiny droplets or direct contact with someone carrying the infection. The best method of preventing the spread of SARS-CoV-2 is to self-isolate and follow all government guidelines following a possible infection.

Read on to find out more about how and when COVID-19 is contagious, and how to treat and prevent the infection.

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

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A 2020 review of data from 5,340 people with SARS-CoV-2 infections suggested that people are most contagious within the first week of illness. The study used the number of detectable viral cells in the upper respiratory tract as a rough measure of how contagious people might be.

The study found that SARS-CoV-2 causes this peak infectious period to occur earlier than other coronaviruses, such as SARS-CoV and MERS-CoV.

The World Health Organization (WHO) suggests that people are likely to be most infectious around 2 days before developing symptoms and in the early stages of their illness.

However, this peak will vary from case to case. For example, people who develop symptoms are more likely to spread the virus because they have a higher viral load than those who have COVID-19 without symptoms.

The symptoms could also increase the likelihood of spreading the virus. For example, coughing could increase the risk of a droplet containing the virus infecting someone else.

WHO states that people who have COVID-19 without symptoms can still transmit the virus. However, more research is necessary to determine how contagious these cases are.

According to the Centers for Disease Control and Prevention (CDC), most people with mild-to-moderate COVID-19 are infectious for up to 14 days following initial exposure. This is known as the incubation period. People typically experience symptoms around 4–5 days after infection.

The CDC also states that the incubation period can vary depending on the case. For example, people with severe illness or weakened immune systems can be infectious for up to 20 days. Tiny parts of SARS-CoV-2 can continue to spread beyond 20 days but is no longer infectious.

The CDC recommends that people with COVID-19 can be around other people if all of the following statements are true:

  • it has been 10 days since they developed symptoms
  • it has been 24 hours since they had a fever, and they have not used fever-reducing medications
  • they have noticed improvements in their symptoms
  • they did not have severe symptoms
  • they are not immunocompromised

Loss of taste and smell can last several weeks or months after recovery. However, the presence of these symptoms alone does not mean a person should avoid social contact.

People can still spread COVID-19 before symptoms develop. The medical term for this period is presymptomatic infection.

COVID-19 is most contagious in the first week after exposure to the virus. Symptoms will typically develop during this week, around 4–5 days after exposure.

WHO states that the most infectious period begins around 2 days before the onset of symptoms.

People without COVID-19 symptoms can still infect others. The medical term for this is asymptomatic infection.

However, there is less information on asymptomatic infection as fewer people without symptoms receive testing than those with symptoms.

A 2021 study in JAMA Network Open estimated that around 24% of COVID-19 cases are the result of asymptomatic infection. These estimates are based on the assumption that 30% of all COVID-19 cases are asymptomatic. However, the true number of asymptomatic cases is still unclear due to the lack of data.

WHO recommends people prevent infections and reduce the spread of COVID-19 by:

  • receiving both doses of COVID-19 vaccination
  • regularly washing hands with soapy water or alcohol-based hand gels
  • keeping a minimum of 3 feet (about 1 meter) from others
  • wearing a face mask in public places
  • covering the mouth and nose while coughing or sneezing
  • avoiding touching the face
  • quitting smoking
  • staying away from others following a suspected or confirmed infection
  • avoiding crowded areas, places with poor ventilation, or indoor spaces
  • following local guidance on staying safe during the pandemic

The CDC recommends that people wear cloth face masks any time they are in a public setting. This will help slow the spread of the virus from people who do not know that they have contracted it, including those who are asymptomatic. People should wear cloth face masks while continuing to practice physical distancing. Note: It is critical that surgical masks and N95 respirators are reserved for healthcare workers.

COVID-19 can cause a range of symptoms, which can be mild to severe. These symptoms typically develop within the first 2–14 days of infection.

The most common symptoms of COVID-19 include:

Less common symptoms can include:

COVID-19 can also cause serious symptoms that require immediate medical attention, such as:

Most cases of COVID-19 cause mild to moderate symptoms and require no or minimal treatment. For example, a 2020 review of data from the Chinese Center for Disease Control and Prevention suggests that around 81% of cases cause mild to moderate symptoms.

Doctors may recommend some treatments to ease the mild to moderate COVID-19 symptoms. For example, doctors might recommend:

  • taking over-the-counter medications for fever, such as ibuprofen
  • drinking plenty of water
  • resting to allow the body to fight the virus

People who are at risk of severe illness or develop severe symptoms should receive treatment in a hospital. The exact treatment will vary from case to case, but may include:

  • oxygen to support breathing
  • antiviral medications to slow the spread of the virus
  • drugs to suppress an overractive immune system
  • treatments for complications, such as damage to the heart or blood vessels

Research is ongoing to develop new methods of treating COVID-19 in hospitals. The National Institute of Health regularly updates its guidance for treating people in hospitals with COVID-19 depending on their disease severity.

People can spread SARS-CoV-2 within the first 2 weeks of infection, but are most contagious during the first week. The virus can spread before symptoms develop and in people who experience no symptoms.

Most people will experience mild to moderate symptoms. However, others may require hospitalization for severe symptoms.