Long COVID has affected millions. Here's what scientists now know.

Ziyad Al-Aly is chief of research and development at VA St. Louis Health Care System and a clinical epidemiologist at Washington University in St. Louis.

Since 2020, the condition known as long COVID-19 has become a widespread disability affecting the health and quality of life of millions of people across the globe and costing economies billions of dollars in reduced productivity of employees and an overall drop in the work force.