激增 (jī zēng) means 'to surge, to increase rapidly' and emphasizes a sudden, sharp, and dramatic rise in numbers, often used for statistics like population, demand, or infections. It is stronger and more sudden than 上涨 (shàng zhǎng), which is a general rise in price/level, and more concrete than 高涨 (gāo zhǎng), which can describe abstract emotions or trends. 飙升 (biāo shēng) is similar but suggests a faster, more extreme skyrocketing.