Before Daniela Alves caught COVID-19 in March, the 31-year-old Londoner regularly worked overtime to accelerate her career as a mobile app designer. Now, she struggles with client meetings, and says persistent fatigue has halved her productivity.

"I was a beast before, but now things are different,” Alves says over Zoom, pausing frequently to catch her breath or cough. "I can’t physically do it, and I’m approaching life differently.”

Alves said she needed three months off work even after experiencing a "mild” infection that didn’t require hospitalization. COVID-19’s lingering effects count her among an expanding population of so-called long-haulers — survivors left with debilitating conditions who represent another insidious dimension of the pandemic.