The health department warned that a measles outbreak first announced last week has spread further.
Three more adult measles cases have been identified since Friday, bringing the outbreak total to 19 cases in Manhattan, the Bronx and Brooklyn, the department said Tuesday.
Five hospitalizations -- one more since Friday -- have occurred since the first case was reported last month.
Ten adults and nine children, from 3 months to 63 years old,have contracted the highly contagious virus.
Authorities are trying to pinpoint the source of the outbreak, which is centered in northern Manhattan. The health department is working with city hospitals to prevent further spread.
"Measles is a highly contagious viral infection characterized by a generalized rash and high fever, accompanied by cough, red eyes and runny nose, lasting five to six days," according to the health department.
The infection typically begins with a rash on the face that moves down the body. Those who contract measles can spread the virus for four days before the rash develops and another four days after it appears.
The health department asks New Yorkers to make sure all household members, including children 1 year old and over, are vaccinated.
As many as one in three people with measles develop complications, including pneumonia, miscarriage, brain inflammation and even death.
For more information, visit the health department website.
Follow Anna Sanders on Twitter @AnnaESanders