The Illinois health officials on Thursday confirmed five cases of babies diagnosed with measles at a suburban Chicago daycare center, adding to the concerns over the rising outbreak of the contagious disease across the United States.

In a statement, the Illinois and Cook County health departments said that the health officials are looking into the cluster of measles cases at Palatine-based KinderCare Learning Center.

Among the infected are children under one- year-old. As the dose of vaccine begins at 12 months, hence all the infants have not been subject to routine measles vaccination.

The health officials, however, not provided details over the source of the infection.

Dr. Nirav Shah, director of the Illinois Department of Public Health, in a statement said, “These cases underscore the need for everyone who is eligible for the vaccine to ensure that they have been vaccinated.  There are certain individuals who, because of their age or clinical condition, cannot be vaccinated.”

Illinois had recently diagnosed an adult with measles. The health officials said that the diagnoses for the adult and two of the five babies were confirmed through lab testing. On the other hand, the test results for the other three cases are still pending. However, they have been diagnosed on the basis of clinical and epidemiological factors.

More than 100 cases of measles have been reported across the United States, with many traced to an outbreak linked to the visit of an infected foreign national to Disneyland theme park in Anaheim, California, in December last year.

The highly contagious respiratory disease, Measles, can have the symptoms like red and sore eyes, fever, cough, runny nose and skin rashes. It can be fatal in some cases when the immune system is very weak.

The US Centers for Disease Control and Prevention (CDC) report shows 644 cases of measles were reported from 27 states in 2014, which is the most since 2000.