(ABC 6 News) — The measles outbreak is expanding in Minnesota as the Department of Health reports there are now 51 cases to date.

Most of the cases consist of children aged 1 to 5 years old. 45 of those cases are in Hennepin County with Anoka, Ramsey, and Dakota Counties making up the rest.

This comes after there were 30 cases reported one month ago. MDH says measles is primarily affecting unvaccinated children.