In late 2021, the World Health Orgazination released a clinical definition of long Covid for the first time. They defined the term as a post-Covid-19 condition where symptoms are present three months after an infection that cannot be explained by a different diagnosis. These symptoms commonly include chronic fatigue, body pain, mood swings, cognitive problems or brain fog, and ongoing respiratory issues.
Other than the SARS-CoV-2 virus, other forms of viruses and bacterium are also known to cause post-infection syndromes such as the Ebola virus, Epstein-Barr virus, and cytomegalovirus. In a recent study published in the journal JAMA, researchers found that an estimated 6.2% of people experienced at least one long Covid symptom three months after recovering from a symptomatic infection.
“Ongoing low-grade inflammation has been postulated to cause these symptoms, but the pathology remains largely unknown and treatments are primarily based on symptom relief,” the researchers wrote in their paper. “The consequences for affected individuals are substantial, and specialized clinics for individuals with Long COVID have arisen to respond to an increasing need for supportive and rehabilitative care.”
In their modeling study, the researchers analyzed data for 1.2 million people from 22 countries who had symptomatic Covid-19 in 2020 and 2021. They pooled this data from a total of 54 studies and two medical record databases. The estimated proportion of individuals with at least one of the three long Covid symptoms was higher among those who were admitted to ICUs (43.1%) than those who recuperated in general hospital wards (27.5%).
Whereas only 5.7% of individuals who were not admitted to the hospital had long Covid. Among those who were hospitalized, the estimated duration of their long Covid symptom was around nine months long and four months for unhospitalized people.
“The risk of Long COVID was greater in females and in those who needed hospitalization for the initial SARS-CoV-2 infection, particularly among those needing ICU care,” the researchers concluded.
“In general, women respond to viral infections with less severe disease and mount higher antibody responses but also have higher rates of adverse reactions to vaccinations and antiviral drugs; X chromosome–linked genes are thought to influence susceptibility to viral infections as well as autoimmune diseases, lending support to autoimmune processes playing a role in the development of Long COVID,” the researchers added in their paper.