New York City authorities declared a public health emergency in Brooklyn due to the 300 cases of measles reported in the city, NYC mayor Bill de Blasio noted.

"We are declaring a public health emergency in Williamsburg due to the 300 cases of measles reported in our city — primarily concentrated in Brooklyn. There's no room for misinformation when it comes to protecting our children. Vaccines are safe and effective. They work," NYC Mayor's Office tweeted.

Measles is a highly contagious infectious disease caused by the measles virus. The measles vaccine is effective at preventing the disease, and is often delivered in combination with other vaccines