What is Long COVID?
10-30% of people infected with COVID-19 will experience persisting problems. Symptoms that last for more than 2 months after COVID-19 infection are referred to as “long COVID” or “post-acute sequelae of SARS-CoV-2 (PASC).”
The most common symptoms are fatigue, pain, trouble concentrating, shortness of breath, dizziness, racing heart rate, and gastrointestinal problems. There are a number of other potential symptoms that include numbness, headaches, sensitivity to light and sound, fevers, rashes, and reactions to foods and other exposures. Symptoms may fluctuate or relapse over time. Similar symptoms can develop after COVID vaccine in some individuals who have never had a COVID-19 infection.
Currently, no one is sure what causes long COVID. The most popular theories are persisting viral infection, persisting inflammation, or damage to small blood vessels from abnormal blood clotting. Different patients may have different causes for their long COVID or more than one of these causes may be playing a role.
Multiple studies suggest that a type of white blood cell called mast cells play a role in long COVID. Mast cells release histamine and other chemicals that can affect a person’s immune system and can cause the symptoms that occur in long COVID. In many individuals with long COVID, there is evidence of a pre-existing dysfunction of mast cells. This may explain why some people develop long COVID after infection.