periodic outbreak

例句：

1. 1. The disease is periodic in its outbreaks.
   这种疾病的爆发是周期性的。
2. 2. The epidemic was periodic in its spread.
   这场流行病的传播是周期性的。
3. 3. The weather patterns are periodic in their occurrence.
   天气模式的出现是周期性的。