Leg pain after a viral illness may occur due to muscle inflammation, weakness, dehydration, transient nerve irritation or post-viral fatigue. Some people feel heaviness, cramps, stiffness or aching in the legs for days or weeks, even after fever and other infection symptoms improve. Poor nutrition, low vitamin levels, and prolonged bed rest during illness can also increase muscle pain and weakness. Treatment usually focuses on reducing inflammation and helping the muscles gradually recover. Doctors commonly use pain relievers, sufficient hydration, rest, light stretching and gentle walking to improve circulation and reduce stiffness. Warm compresses, proper sleep and balanced nutrition with enough protein can also support recovery. In some people, a vitamin D, calcium or electrolyte imbalance can cause persistent body pain after illness. Sudden swelling in one leg, redness, severe weakness, numbness or difficulty walking can sometimes indicate circulation or nerve-related problems and may require further medical attention.