The first, "acute", phase usually causes fever, muscle pain with prominent backache, headache, shivers, loss of appetite, and nausea or vomiting.

第一期也称“急性期”，通常的特征是发热、肌肉疼痛（尤其是背痛）、头痛、寒战、食欲不振、恶心和呕吐。