Scientists are still learning about COVID-19 and the impacts of long COVID-19, also referred to as post-acute COVID-19 syndrome, long-haul COVID-19, and post-COVID-19 syndrome. People with long COVID-19 often experience a wide range of symptoms, which can be influenced by their previous health issues and the severity of their COVID-19 infection.

COVID-19 is caused by infection with the virus SARS-CoV-2. Since COVID-19 is a relatively new disease, nobody is sure exactly how long people will be impacted by symptoms like respiratory issues, “brain fog,” fatigue, or a loss of taste or smell. As the COVID-19 pandemic continues, scientists and health providers continue to study data on those with long COVID-19 to learn more.

How Long Is “Long”?

Many people seem to recover from COVID-19 in just a few weeks. Most health organizations currently define long COVID-19 as symptoms of COVID-19 that last longer than 12 weeks and are not caused by another diagnosis. Recent studies show that some people can have COVID-19 symptoms for several months, with rare cases of even longer infections or symptoms due to a weakened immune system.

The World Health Organization (WHO) published a definition for the “post COVID-19 condition,” describing it as a condition that “occurs in individuals with a history of probable or confirmed SARS-CoV-2 infection, usually 3 months from the onset of COVID-19 with symptoms and that last for at least 2 months and cannot be explained by an alternative diagnosis.”

Long COVID-19 in People Hospitalized With COVID-19

Several studies have tried to understand the duration of long COVID-19 by examining people who were hospitalized with COVID-19. An Italian study of 143 previously hospitalized people found that 87.4 percent reported still suffering from at least one symptom 60 days after the onset of COVID-19. Fatigue and trouble breathing (dyspnea) were the most common symptoms, followed by joint pain and chest pain.

A follow-up study in Wuhan, China of more than 1,700 people discharged from the hospital after COVID-19 infection noted that, after six months, 63 percent suffered from fatigue or muscle weakness, 26 percent reported sleep difficulties, and 23 percent said they experienced anxiety or depression.

In extreme cases, people may experience long COVID-19 for up to a year. A preprint (not yet peer-reviewed) study describes a woman who was infected with the coronavirus and experienced symptoms for nearly a year. The length of her illness was due to previous cancer treatments that left her immune system unable to fight off the infection. Though she was treated with antiviral drugs and antibodies to fend off the virus, this rare case shows how people with weakened immune systems may experience long COVID-19.

People who were hospitalized with severe COVID-19 can have symptoms for months after the initial infection. Hospitalization and staying in an intensive care unit (ICU) can also lead to post-intensive care syndrome (PICS), which causes mental health problems, cognitive impairments, and physical impairments.

A review of studies on people who had severe COVID-19 showed that 16 percent also developed post-traumatic stress disorder (PTSD). Symptoms from PICS or PTSD may be confused with COVID-19-specific symptoms for people who were treated in the ICU for severe COVID-19.

Understanding the duration of COVID-19 symptoms in people who have either severe or mild COVID-19 will help researchers better estimate the length of long COVID-19.

Long COVID-19 in the General Population

Long COVID-19 does not only affect people who had severe COVID-19. People with mild COVID-19 can also develop long-term symptoms.

One study used data from the COVID Symptom Study smartphone app to understand how COVID-19 affects the general population. From March 2020 to September 2020, over 4 million people registered with the app to log their COVID-19 test results and symptoms.

Researchers analyzed the responses of 4,182 people who had started logging their health on the app while healthy and later tested positive for COVID-19. Of this group, 13.3 percent had symptoms lasting longer than 28 days, 4.5 percent had symptoms for over eight weeks, and 2.3 percent had symptoms for over 12 weeks.

People who reported COVID-19 symptoms on the app for four weeks or longer most commonly experienced fatigue and headaches. Researchers noted that people who had more than five symptoms in the first week of infection were more likely to develop long COVID-19.

Evidence From History

Previous coronavirus outbreaks may give us clues as to how COVID-19 may persist.

The virus that causes COVID-19 (SARS-CoV-2) is a close relative of another coronavirus called SARS-CoV, which caused the SARS pandemic in 2003. Compared to the COVID-19 pandemic, the SARS pandemic did not spread as widely or infect as many people. Though these two coronaviruses are different, the SARS pandemic may give us an idea of what people affected by COVID-19 can expect in the long run.

One 2009 Hong Kong study reported on the long-term symptoms of 233 SARS survivors about three-and-a-half years after they recovered from acute SARS infection. At that time, about 40 percent reported mental health issues, and 40 percent also reported feeling chronic fatigue.

One of the longest follow-up studies on people affected by SARS found that some still had limited lung function 15 years after they were discharged from the hospital.

While these studies suggest that the effects of SARS can last for several years, they largely focused on people who suffered from severe SARS and were hospitalized. SARS is a more severe disease than COVID-19. Thus, while these studies can help us learn more about coronavirus diseases, they likely represent a worst-case scenario.

Reducing the Risk of Long COVID-19

Vaccination can help prevent long COVID-19 by reducing the risk of contracting the coronavirus. One study using data from the COVID Symptom Study app followed nearly 1 million people who got two doses of a COVID-19 vaccine. Among them, 0.2 percent reported later testing positive for COVID-19. The researchers found that people who had been fully vaccinated were only about half as likely as unvaccinated people to develop long COVID-19 if they tested positive for COVID-19.

Find Your Team

On myCOVIDteam, the social network for people with long COVID-19 and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with COVID-19.

Have you experienced long COVID-19? How long did your symptoms last? Share your experience in the comments below, or start a conversation by posting on your Activities page.