The Allen County Health Department confirmed one case of measles Thursday afternoon.
Officials say the patient is an unvaccinated minor who is stable and recovering.
The confirmation is part of an investigation conducted with the Indiana Department of Health. Two cases were confirmed Wednesday in Adams County.
The IDOH has identified at least 18 cases now around the state, most of which have been concentrated in Switzerland and Wayne counties in southeast Indiana.
Allen County Health Department Administrator Mindy Waldron says "now is the time for our community to get vaccinated." She asks all to check their vaccination status and seek immunization for everyone eligible.
Symptoms include rash, high fever, cough, watery eyes and runny nose. In some cases, the virus can cause pneumonia and brain swelling. It can be fatal in young children.
The highly-infectious virus has spread nationwide, recently killing four in Pennsylvania according to state officials there.
Pennsylvania officials have expressed concern about statements of vaccine hesitancy and misinformation attributed to the Trump administration.
Indiana health officials say that if one person has measles, up to 9 or 10 people nearby will become infected if not protected.
The most effective way to protect against the spread of the disease is with the MMR—or mumps, measles and rubella—vaccine.
