Understanding Long COVID: A Comprehensive Guide
Nearly three years after the initial surge of the SARS-CoV-2 pandemic, an estimated 80 million to 400 million people worldwide are living with long COVID, a chronic condition impacting millions globally.1 This complex illness, characterized by a wide range of symptoms, continues to pose a significant public health challenge. While novel cases of Long COVID are decreasing compared to the early pandemic stages, it remains a serious concern.1
What is Long COVID?
Long COVID, similarly known as post-acute sequelae of SARS-CoV-2 (PASC), is defined as a chronic condition that occurs after a SARS-CoV-2 infection and lasts for at least three months.1 It can manifest in a diverse array of symptoms and conditions that may fluctuate in severity or persist over extended periods—months or even years.1,3 Anyone who has been infected with SARS-CoV-2, including children, can develop Long COVID.1,3 Importantly, a positive SARS-CoV-2 test is not required for a diagnosis.1 Some individuals may develop Long COVID without ever knowing they were initially infected.3 Repeated infections with SARS-CoV-2 increase the risk of developing Long COVID.1
Symptoms and Conditions
Long COVID is associated with over 200 different symptoms, impacting multiple body systems. Common symptoms include:
- Fatigue
- Shortness of breath
- Cognitive dysfunction (brain fog)
- Sleep disorders
- Depression
- Memory loss
These symptoms can range from mild to severe and may require comprehensive medical care, sometimes leading to disability.1
Underlying Mechanisms
Researchers are actively investigating the underlying causes of Long COVID. Several potential mechanisms have been identified, including:
- Viral Persistence: The SARS-CoV-2 virus may persist in the body, contributing to ongoing symptoms.
- Reactivation of Herpesviruses: Immune stress from COVID-19 can reactivate latent herpesviruses.
- Chronic Immune Activation: The immune system may remain chronically activated, leading to inflammation and tissue damage.
- Immune System Dysregulation: Imbalances in the immune system’s function.
- Microbiota Dysbiosis: An imbalance in the gut microbiome.
- Coagulation Abnormalities: Issues with blood clotting.
- Endothelial Damage: Damage to the lining of blood vessels.
- Neurological Changes: Structural and functional changes in the brain.
Diagnosis and Testing
Currently, there are no approved tests specifically designed to diagnose Long COVID.1 Diagnosis relies on a clinical evaluation, considering a recent history of SARS-CoV-2 infection and persistent or recurring symptoms for at least three months.1 Other potential conditions must be ruled out through blood tests, imaging, electrocardiography, and echocardiography.1
Impact on Quality of Life and the Economy
Long COVID significantly impacts quality of life, leading to job loss, income reduction, and difficulty returning to work.1 Individuals may experience periods of fluctuating health, depression, and reduced activity levels.1
The economic consequences are substantial. A 2024 study estimated that Long COVID resulted in over 803 million lost work hours in Brazil alone, costing more than USD 11 billion.1 Globally, Long COVID could have an annual economic impact of approximately USD 1 trillion—about 1% of the global economy.1
Prevention and Management
Currently, the most effective way to prevent Long COVID is to avoid SARS-CoV-2 infection through vaccination and by minimizing reinfection.1,3 There are currently no approved treatments specifically for Long COVID, highlighting the need for further research.1
Ongoing Research and Future Directions
Significant progress in understanding Long COVID requires further scientific studies to standardize definitions, improve diagnostic tools, and develop effective therapies.1 Researchers are focusing on diverse patient populations and considering the role of social and health determinants in the development and progression of Long COVID.1 The National Institutes of Health (NIH) and the RECOVER Initiative are committed to learning more about the long-term effects of COVID-19.3
Long COVID in Brazil
While reported cases of COVID-19 in Brazil have decreased in recent years (approximately 432,400 cases in 2025 compared to 984,000 in the previous year), the condition remains prevalent.1 As of 2025, an estimated 13.8 million cases of “post-COVID conditions” have been reported in Brazil, with women and individuals aged 30-49 being most affected.1 Brazil’s national public health system, the SUS, has been monitoring Long COVID since 2021.1
Addressing Stigma
Patients with Long COVID often face stigma, discrimination, and inadequate access to care and support.1 These experiences can be particularly challenging for individuals from ethnic minorities.1 Multidisciplinary care teams are recommended to provide comprehensive support.1
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