Since 1948 three generations of residents in Framingham have participated in regular medical examinations originally intended to study the spread of heart disease.
自1948年，有三代弗雷明汉的居民参与到常规的健康体检中，最初的目的为了研究心脏病的传播。
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Adequate supplies of safe-drinking water and proper disposal of sewage within communities, combined with personal hygiene practices, such as regular hand-washing, reduce the spread of HAV.
Normally the sinoatrial node generates regular electrical pulses that spread across the Chambers of the heart, causing the cells to contract in synchrony.