Write a composition of at least 150 words about the topic :Epidemic Diseases and Public Health Crises.You should write according to the outline given below: 1.流行性疾病爆发的原因及其对公共健康的影响 2.举例说明如何有效地预防流行性疾病,公共健康危机 3.对全文作出总结 Write your answers on the ANSWER SHEET.