We've always had marginal/debatable illness. The existence of Chronic Lime Disease is debated, similar to Fibromyalgia, or perhaps Chronic Fatigue. Havana Syndrome is a more recent example. It's possible that these are actualy manifestations of psychological conditions like depression/anxiety, but people have a hard time accepting that. Doctors debate this, and I'm not a doctor. Who knows, maybe these are lingering conditions brought on by flus or other viruses.