 COVID-19 has been linked to a variety of long-term health complications, collectively known as post-acute sequelae of SARS-CoV-2 infection, PASC. These can range from mild to severe and often involve multiple organ systems. Symptoms can include fatigue, post-exertional malaise, and cognitive dysfunction, which can persist for months and have a significant impact on daily life. There are also many potential causes of these symptoms, including direct effects of the virus itself, as well as secondary effects caused by other viruses, bacteria, and even environmental factors. Understanding the underlying mechanisms behind PASC is key to developing effective treatments and preventative measures. This article was authored by Zuckie Sheriff, Christian Argomes, Thomas J. Connors, and others.