4. Nausea and vomiting
As the prodromal syndrome ends, one of the first symptoms that may appear is nausea, and sometimes vomiting. In this phase, the disease progresses very quickly, and other symptoms appear almost at the same time, including abdominal tenderness, weakness, and sometimes diarrhea. This symptom usually appears after a period of up to 10 days when patients only feels myalgias, mild fever, and chills. In some cases, nausea and vomiting can be included in the prodromal syndrome.