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What is Long COVID?

Long COVID terms and definitions development explained

In April 2020, shortly after the beginning of the pandemic, anecdotal reports from patients started to emerge that previously healthy individuals were experiencing lingering symptoms and were not fully recovering from an infection with SARS-CoV-2. These patients started to refer to themselves as “Long Haulers,” and they coined the term “Long COVID.” This early recognition by the patient community, and their efforts to organize, colloquially name the condition, and alert the world to study it, galvanized the scientific community to pursue research programs in this area, which in a short period of time have resulted in substantial conceptual advances and significant breakthroughs.

In Chapter 1 (page 14) of both the National Research Action Plan on Long COVID and the Services and Supports for the Longer-term Impacts of COVID-19, the following interim federal working definition is presented in a call out box. “Long COVID is broadly defined as signs, symptoms, and conditions that continue or develop after initial COVID-19 or SARS-CoV-2 infection. The signs, symptoms, and conditions are present four weeks or more after the initial phase of infection; may be multisystemic; and may present with a relapsing– remitting pattern and progression or worsening over time, with the possibility of severe and life-threatening events even months or years after infection. Long COVID is not one condition. It represents many potentially overlapping entities, likely with different biological causes and different sets of risk factors and outcomes.”

This working definition was developed by the U.S. Department of Health and Human Services in collaboration with other departments including with subject matter experts at HHS Office of the Secretary, CDC, and NIH and coincident with engagement of patient groups, medical societies, and experts inside and outside the government. The definition builds on CDC’s definition of Post-COVID-19 Conditions (PCC), conceptually first described by CDC in November 2020 and first labeled PCC in February 2021. Terms and definitions for these conditions have evolved since the beginning of the pandemic and will continue to evolve as we learn more about the symptoms and conditions associated with Long COVID. In addition to Long COVID and PCC, an additional term had emerged in parallel and is in general usage in the United States: Post-Acute Sequelae of SARS-CoV-2 infection (PASC). While Long COVID is largely a lay term, PCC and PASC are two scientific technical terms. PCC covers a wide range of health consequences that are due to all effects of COVID-19, including secondary and tertiary effects. PASC refers to the direct and indirect consequences of SARS-CoV-2 on human health.

To further develop this interim Long COVID definition and to better align current definitions used in clinical care, surveillance, and research, HHS will convene public and private partners as called for in the National Research Action Plan.