The US Centers for Disease Control and Prevention (CDC) defines long COVID as a chronic condition that occurs after SARS-CoV-2 infection and is present for at least 3 months; it includes a wide range of symptoms or conditions that may improve, worsen, or be ongoing. As of early 2023, an estimated 6.9% of US adults reported ever experiencing long COVID.
2024 National Academies of Sciences, Engineering, and Medicine Definition
Long COVID is an infection-associated chronic condition that occurs after SARS-CoV-2 infection and is present for at least 3 months as a continuous, relapsing and remitting, or progressive disease state that affects one or more organ systems. Any organ system can be involved, and the condition can manifest in multiple ways.
Patients can present with:
- Single or multiple symptoms, such as shortness of breath, cough, persistent fatigue, post-exertional malaise, difficulty concentrating, memory changes, recurring headache, lightheadedness, fast heart rate, sleep disturbance, problems with taste or smell, bloating, constipation, and diarrhea.
- Single or multiple diagnosable conditions, such as interstitial lung disease and hypoxemia, cardiovascular disease and arrhythmias, cognitive impairment, mood disorders, anxiety, migraine, stroke, blood clots, chronic kidney disease, postural orthostatic tachycardia syndrome (POTS) and other forms of dysautonomia, myalgic encephalomyelitis / chronic fatigue syndrome, mast cell activation syndrome, fibromyalgia, connective tissue diseases, hyperlipidemia, diabetes, and autoimmune disorders such as lupus, rheumatoid arthritis, and Sjögren syndrome.
- It can follow asymptomatic, mild, or severe SARS-CoV-2 infection. Previous infections may have been recognized or unrecognized.
- It can be continuous from the time of acute SARS-CoV-2 infection or have a delayed onset for weeks or months after what had appeared to be full recovery from acute infection.
- It can affect children and adults, regardless of health, disability, or socioeconomic status, age, sex, sexual orientation, race, ethnic group, or geographic location.
- It can exacerbate preexisting health conditions or present as new conditions.
- It can range from mild to severe and can resolve over a period of months or can persist for months or years.
- It can be diagnosed on clinical grounds; no biomarker that is currently available conclusively determines the presence of this condition.
- It can impair patients' ability to work, attend school, take care of family, and care for themselves, resulting in profound emotional and physical effects on the patients, their families, and caregivers.
Symptoms can persist beyond 6 months in some individuals, although patients most often progressively improve with time. Eventually, most patients report returning to their usual state of health. A population-based cohort study of over 3000 patients found that fatigue and cognitive dysfunction were common sequelae after SARS-CoV-2 infection, with many of these symptoms improving over 2 years.
The pathophysiology of PCCs is still unknown. There are no specific laboratory abnormalities or imaging findings necessary for the diagnosis of PCCs.
PCCs can develop regardless of initial COVID-19 illness severity. Risk factors include older age, partial or no vaccination, female sex, more than 5 symptoms in the first week of acute infection, and comorbid illness, such as diabetes and chronic kidney disease.
In a large study, about one-fifth of fully vaccinated patients diagnosed with breakthrough infection reported having long-COVID symptoms at 6 weeks after diagnosis. Another published study found that vaccination was protective against development of PCCs; those who were fully vaccinated when they contracted SARS-CoV-2 developed PCCs at approximately half the rate of those who were unvaccinated when they contracted SARS-CoV-2 (5.2% versus 10.7%, respectively). In a population-based probability sample of 4695 adults with COVID-19, long COVID prevalence was 40%-60% lower among adults vaccinated (versus unvaccinated) prior to their COVID-19 onset.
As more is learned about the long-term effects of COVID-19 in some individuals, durable cutaneous manifestations have been observed. See skin and oral mucosal manifestations of COVID-19.
Pediatric patient considerations: Data from the CDC suggest that the prevalence of long COVID is around 1%-2% of children who have had COVID-19, although some estimates have been as high as 10%-20%. The most frequently reported symptoms in children include fatigue, brain fog, and headaches; however, symptoms affecting virtually all body systems have been described. In severe cases, some children may experience respiratory and cardiovascular problems (including myocarditis). An increased rate of new-onset type 1 and type 2 diabetes mellitus as well as more severe episodes of diabetic ketoacidosis have also been observed. Special attention should be paid to patients with preexisting intellectual or developmental disabilities as well as those who have a complex medical history, as new symptoms and conditions may be overlooked.
Related topics: multisystem inflammatory syndrome in adults (MIS-A), multisystem inflammatory syndrome in children (MIS-C)
