The outbreak began last October and has been largely confined to children living in Brooklyn's Orthodox Jewish communities. Two of the 61 cases confirmed since last Thursday are pregnant women, according to Reuters, citing the city's health department. 

The Health Department took the unusual step earlier this month of issuing an emergency order requiring unvaccinated people in affected neighborhoods to get the measles, mumps and rubella, or MMR, vaccine unless they could otherwise show they had immunity.

The 12 people issued summons for defying the order must attend a hearing and face a fine of up to $1,000 if found to be noncompliant. -Reuters

NYC's outbreak is one of the largest of several across the country, which has confirmed 695 measles cases so far this year - the most since the virus was declared eliminated in 2000, according to the US Centers for Disease Control and Prevention in a Wednesday statement.