As of Tuesday, the number of confirmed cases of measles in New York City has risen to 20 incidents, nine of which involve children.
The city's health department announced the new total amid an investigation into whether the highly contagious disease was spread in several medical facilities after workers failed to properly identify and treat symptoms quickly.
The New York Times reports only three of the 11 infected adults had records proving they were vaccinated. Seven of the nine children were too young to be vaccinated. Following the wishes of their parents, the other two children had not been vaccinated.
Officials would not say where the latest case was identified, but a majority of them have been concentrated in northern Manhattan.
Since the first known outbreak of the disease in early February, 16 Manhattan residents, three Bronx residents, and one Brooklyn resident have been infected.
“We know a number of people were exposed and possibly got their infection either at a doctor’s office or at an emergency room where they went and it took more time than it should have for them to be put in an isolation area where they couldn’t possibly infect anyone else,” the city's deputy commissioner of disease control Dr. Jay Varma told The Times.
The United States was thought to have eradicated measles in 2000, but the number of reported outbreaks has grown in recent years, alarming officials as vaccination rates have also fallen.
In 2013, measles incidents tripled with 58 out of 175 cases identified in Brooklyn alone after parents in two Jewish communities refused to vaccinate their children in misguided fear that immunization will lead to autism.