How do hantavirus symptoms differ from the flu?

Early hantavirus and flu symptoms overlap significantly: both cause fever, fatigue, muscle aches, and headache. Key differentiators: (1) Hantavirus muscle pain is often severe and concentrates in large muscle groups (thighs, hips, lower back); flu pain is more diffuse. (2) Hantavirus rarely causes upper respiratory symptoms early on (no runny nose, sore throat); flu commonly does. (3) Hantavirus progresses to rapid respiratory deterioration 4-10 days after onset (HPS phase) — a hallmark not seen in flu. (4) Hantavirus has no seasonal pattern; flu peaks in winter. The most important practical question: 'Have you had recent rodent exposure or traveled to endemic areas?' If yes and you have flu-like symptoms, get medical attention promptly — early hospitalization significantly improves hantavirus outcomes.