noun, する verb
A sudden increase is just that, a sudden increase or surge!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
What do you think about the sudden increase in the number of young people who lack self-control in recent years, Dr. Fugu?
I feel that there's been a sudden increase in the number of people who can't accept even the slightest criticism.
The number of children who dream of being a choreographer has increased suddenly.