Language Point 41

Especially the very young, the elderly and cigarette smokers are at high risk. (Para. 30)
Meaning: Especially children, old men and women, and cigarette smokers are more in danger from air pollution.
at risk: in danger
The disease is spreading, and all children under 5 are at risk.

这疾病正在蔓延，五岁以下的儿童都有被传染的危险。