Experts convened by the National Academies of Sciences, Engineering, and Medicine released an updated definition of long Covid on Tuesday. In their report, the group defined LC as, “an infection-associated chronic condition that occurs after SARS-CoV-2 infection and is present for at least three months as a continuous, relapsing and remitting, or progressive disease state that affects one or more organ systems.” They recommended that this definition should be adopted by government officials, healthcare workers, employers, and educators.
The panel recognized that long Covid can result from severe, mild, or even asymptomatic infections. They also noted that long Covid, “does not require laboratory confirmation or other proof of the initial infection.” Finally, they did not specify a maximum time after infection during which LC can develop.
The etiology of long Covid remains unknown. Researchers have hypothesized that various factors may lead to its development, including some form of autoimmunity caused by the initial SARS-CoV-2 infection or sequestered reservoirs of the virus within the body. Other researchers have speculated that alterations in the gut microbiome associated with Covid-19 may lead to the development of long Covid.
The number of people affected by long Covid also is unknown. In one report, researchers estimated that it may affect 5.8 million children in the U. S. Other researchers placed that number much lower. Researchers in the Netherlands estimated that about 12.5% of adults who had Covid-19 exhibit post-Covid sequelae. Researchers in the U. S. suggested that the prevalence is under 7%.
These disparate estimates largely result from the ill-defined nature of long Covid. Over 200 symptoms, affecting every organ system, have been associated with the condition. People often report brain fog and fatigue. Existing conditions like diabetes or heart disease may worsen. It can manifest as a continuation of an acute SARS-CoV-2 infection, or symptoms can develop weeks or months after an infection. For some people, symptoms resolve in a relatively short period of time. For others, symptoms persist. No biomarkers associated with long Covid have been identified.
With a standardized definition of long Covid, data from different studies can be more easily compared. More importantly, a standardized definition may lead to improved patient care. Indeed, Dr. Harvey Fineberg, chair of the NASEM committee, remarked, “The lack of a consistent definition for Long COVID has hampered research and delayed diagnosis and care for patients.” He went on to note that, “Our committee hopes this single definition, crafted with input from across research and patient communities, will help to educate the public about this widespread and highly consequential disease state.”
A common definition for long Covid will not make it go away. It will not alleviate any of the symptoms. But it may help people with long Covid get the medical care that they deserve.
