It's one of medicine's biggest mysteries — why sometimes our immune system attacks our own bodies. Autoimmune diseases affect as many as 50 million Americans and millions more worldwide. They're hard to diagnose and treat, and they're on the rise. A Massachusetts woman's journey with one named lupus — called the disease of 1,000 faces for its baffling variety of symptoms — offers a snapshot of the burden. Now researchers are decoding the biology behind these debilitating diseases in hopes of eventually treating the causes, not just the symptoms.

People with immune system health problems continue to take precautions against COVID-19 five years into the pandemic. The threat of infection is a governing force in their lives while others speak of the coronavirus in the past tense. They protect themselves from the virus with masks and isolate themselves in small family bubbles. In online support groups, they trade research about the danger of repeat infections and cognitive impairment. They miss the empathy they felt during the early days of the pandemic. Some have lost friendships, but they strive to maintain the social ties important to mental health.