By Aadit Jain (‘23)
According to Medical News Today, the WHO defines “post-COVID-19” as the “…condition [that] occurs in individuals with a history of probable or confirmed SARS-CoV-2 infection, usually 3 months from the onset of COVID-19 with symptoms that last for at least 2 months and cannot be explained by an alternative diagnosis.” Usually, symptoms from COVID-19 end within a few weeks of infection. However, some symptoms appear or persist months after infections: these cases become known as “long COVID” or “post-COVID-19.” Symptoms of long COVID include constant fatigue, difficulty breathing, and cognitive problems.
As the NPR reports, scientists have not yet been able to pinpoint the frequency of long COVID, with estimates ranging from 5% of all COVID-19 cases to 60%. However, studies do consistently show that the risk of having long COVID increases with severe illness (such as in cases of hospitalizations). This is because inflammation from the virus or the body’s response to it can cause organ damage (in the heart, brains, and lungs, for example); researchers have also found evidence of high inflammation as a result of the body’s response to the COVID-19 virus. Inflammation and organ damage could be one of the causes of long COVID.
An NPR article reports that scientists have not yet fully understood the cause of long COVID, though they have several theories on what may be the issue. Perhaps it is the result of the COVID-19 virus still lurking in the body. It can also be the impact of the virus on the immune system: it may stay active long term to defend against future COVID infections. Researchers at Yale have also found solid evidence of higher levels of cytokines (chemical messengers that allow the immune system to communicate) and autoantibodies (proteins that hurt cells of the body instead of the virus) in the blood of COVID patients. This could be an indicator of the severe impact that the virus has on the immune system long term, causing symptoms to persist for months. Still, more research is necessary to conclude what exactly is causing long COVID.