"Measles virus can live for up to two hours in an airspace where the infected person coughed or sneezed", according to the CDC.
Two of the cases were reported in children under the age of one in New Haven county.
Symptoms include a mild-to-moderate fever, a cough, runny nose, red eyes and a sore throat.
107 people were reported to have measles from January 1 to July 14. A majority of the people who got measles weren't vaccinated.More news: Mou dares Pogba to hand in transfer request
More news: Modric named in Real Madrid squad amid Inter links
More news: Man Arrested After Car Crashes Into Barrier Outside UK Parliament
In 2017, 118 cases were reported.
Some people may suffer more severe complications: ear infections, pneumonia and encephalitis (swelling of the brain which occasionally develops 5-10 years later), these unfortunately may result in prolonged hospitalization or even death. Vaccination is now the only effective way to prevent measles.
The measles vaccine - known as the MMR or measles, mumps and rubella vaccine - is very effective.
In addition to IN, the other states being monitored are Arkansas, California, Connecticut, Florida, Illinois, Kansas, Louisiana, Maryland, Michigan, Missouri, Nevada, New Jersey, New York, North Carolina, Oklahoma, Oregon, Pennsylvania, Tennessee, Texas, and Washington, and Washington D.C.
Most of the people who got measles had not been vaccinated, the CDC said.