In a new review article, researchers from the Universities of Arizona, Oxford and Leeds analyzed dozens of previous studies on long COVID to examine the number and range of people affected, the underlying mechanisms of the disease, the numerous symptoms patients develop, and current and future treatments.
Long COVID, also known as post-COVID-19 illness, is generally defined as the persistence of symptoms for three months or more after acute COVID-19. The disease can affect and damage many organ systems, leading to severe, long-term impairment in function and a wide range of symptoms, including fatigue, cognitive decline (often referred to as “brain fog”), shortness of breath, and pain.
Long COVID can affect almost anyone, including all age groups and children. It is more common in women and people of lower socioeconomic status, and the reasons for these differences are being studied. Researchers have found that while some people gradually get better from long COVID, in others the condition can persist for years. Many people who developed long COVID before vaccines arrived are still unwell.
“Long COVID is a devastating disease with profound human costs and socioeconomic impacts,” said Janko Nikolich, Ph.D., senior author on the paper, director of the Aegis Consortium in the U of A College of Health Sciences, professor and head of the Department of Immunobiology at the U of A College of Medicine in Tucson, and a member of the BIO5 Institute. “By studying it in detail, we hope to understand the mechanisms and find targets for therapy against this disease, but also potentially against other complex chronic infection-associated conditions such as myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia.”
If a person has been fully vaccinated and is up to date on their booster doses, their risk of developing long COVID is much lower. However, 3% to 5% of people worldwide still develop long COVID after an acute COVID-19 infection. According to the Centers for Disease Control and Prevention, long COVID affects an estimated 4% to 10% of the U.S. adult population, and 1 in 10 adults who had COVID develop long COVID.
The review study also found that a wide range of biological mechanisms were involved, including persistence of the original virus in the body, disruption of the normal immune response and microscopic blood clotting, even in some people who only had mild initial infections.
There are no proven treatments for long COVID yet, and current treatment for the disease focuses on ways to alleviate symptoms or provide rehabilitation. Researchers say there is a pressing need to develop and test biomarkers, such as blood tests, to diagnose and monitor long COVID and find therapies that address the underlying causes of the disease.
People can reduce their risk of developing long COVID-19 by avoiding infection (for example, by wearing a tight-fitting mask in crowded indoor spaces), taking antivirals promptly if they get COVID-19, avoiding strenuous exercise during such infections, and making sure they stay up to date with COVID-19 vaccines and boosters.
“Long COVID is a daunting disease, but there is reason for cautious optimism,” said Trisha Greenhalgh, senior author of the study and a professor at Oxford’s Nuffield Department of Primary Care Health Sciences. “A variety of mechanism-based treatments are being tested in research trials. If effective, they would allow us to target specific subgroups of people with precision therapies. Treatments aside, it is increasingly clear that long COVID places a huge social and economic burden on individuals, families and society. In particular, we need to find better ways to treat and support ‘long haulers’ – people who have been ill for two years or more and whose lives have often been turned upside down.”
The full article, “Long COVID: A Clinical Update,” is published in The lancet.