Long COVID a.k.a. post-COVID-19 syndrome, post-acute sequelae of COVID-19 (PASC), chronic COVID syndrome (CCS) and long-haul COVID is a condition characterized by long-term sequelae — appearing or persisting after the typical convalescence period — of coronavirus disease 2019 (COVID-19).

Earlier in the pandemic, it appeared that the majority of people infected with the coronavirus experienced mild-to-moderate symptoms and generally recovered within two to three weeks, depending on the severity of their illness. However, as time has passed, it’s become clear that some people, regardless of the severity of their disease, continue to experience symptoms beyond the acute phase of infection. This has become known as “long COVID”.

Long COVID is a patient-created term that was reportedly first used in May 2020 as a hashtag on Twitter by Elisa Perego, an archaeologist at University College London.

Long COVID has no single, strict definition. It is normal and expected that people who experience severe symptoms or complications such as post-intensive care syndrome or secondary infections will naturally take longer to recover than people who had mild illness and no such complications.

One rule of thumb is that long COVID represents symptoms that have been present for longer than two months, though there is no reason to believe that this choice of cutoff is specific to infection with the SARS-CoV-2 virus.

Most people who catch COVID-19 won’t become severely ill and get better relatively quickly. But significant numbers have had long-term problems after recovering from the original infection — even if they weren’t very ill in the first place. Post-COVID conditions are a wide range of new, returning, or ongoing health problems people can experience four or more weeks after first being infected with the virus that causes COVID-19. These conditions can have different types and combinations of health problems for different lengths of time.

According to Centers for Disease Control and Prevention (CDC), some people are experiencing a range of new or ongoing symptoms that can last weeks or months after first being infected with the virus that causes COVID-19. Unlike some of the other types of post-COVID conditions that only tend to occur in people who have had a severe illness, these symptoms can happen to anyone who has had COVID-19, even if the illness was mild, or if they had no initial symptoms.

People commonly report experiencing different combinations of the following symptoms:

• Difficulty breathing or shortness of breath
• Tiredness or fatigue
• Symptoms that get worse after physical or mental activities
• Difficulty thinking or concentrating (sometimes referred to as “brain fog”)
• Cough
• Chest or stomach pain
• Headache
• Fast-beating or pounding heart (also known as heart palpitations)
• Joint or muscle pain
• Pins-and-needles feeling
• Diarrhoea
• Sleep problems
• Fever
• Dizziness on standing (lightheadedness)
• Rash
• Mood changes
• Change in smell or taste
• Changes in period cycles

The respiratory tract is the site of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry and infection; however, COVID-19 is a complex systemic disease, affecting the cardiovascular, renal, hematologic, gastrointestinal and central nervous systems. As evidence emerges of predominantly lasting impairment of lung function related to fibrosis, more data on the long-term effects of COVID-19 on other organs are required.

Researchers don’t know why symptoms linger but believe some symptoms reflect lung scarring or damage to other organs from severe initial infections. Another theory suggests that the virus may linger in the body and trigger an immune response that leads to the symptoms.

Multi-organ effects can affect most, if not all, body systems, including heart, lung, kidney, skin, and brain functions. Autoimmune conditions happen when your immune system attacks healthy cells in your body by mistake, causing inflammation (painful swelling) or tissue damage in the affected parts of the body.

There is currently no test – instead, it is currently a “diagnosis of exclusion” with doctors first ruling out other possible causes. After a year and a half, the risk of long COVID is one of the pandemic’s biggest and least-addressed unknowns.

Some estimates indicate about 30% of unvaccinated COVID-19 patients develop long-term symptoms, including shortness of breath, fatigue, difficulty concentrating, insomnia and brain fog.

The best way to prevent COVID is by getting vaccinated against COVID-19 as soon as you can. Avoid physical contact and don’t forget to use masks in public places.

Roughly half of the people with long COVID reported an improvement in their symptoms after being jabbed — possibly by resetting their immune response or helping the body attack any remaining fragments of the virus, say experts.

Vaccination can also help prevent people from contracting the virus and developing long COVID in the first place. Using masks in public places are to be continued as a practice even after vaccination. We need to follow the COVID appropriate behaviour.

Past pandemics have led to changes in the way we live that we’ve come to accept as normal. Screens on our doors and windows helped keep out mosquitos that carried yellow fever and malaria. Sewer systems and access to clean water helped eliminate typhoid and cholera epidemics. Perhaps the lessons learned from COVID-19 might yield similar long-term improvements in our health system.