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。

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

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临床可表现为恶心、呕吐、腹痛、消化道出血、食欲不振、消瘦、头痛、头昏等。

The clinical manifestations included nausea, vomiting, abdominal pain, abdominal distention, gastrointestinal bleeding, poor appetite, marasmus, headache, dizziness and etc.

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