According to the Orange County Health Care Agency, the toddler recently traveled domestically. The agency is notifying anyone who may have been exposed to the child in a health care setting.
"No additional community exposure is suspected" because the toddler's family isolated during the contagious period, the agency added.
According to the Centers for Disease Control and Prevention, 1,514 cases of measles have been reported nationwide with 23 new ones in the past couple of weeks. That is the highest annual case count in more than 30 years.
"Measles is a highly contagious virus that can cause severe illness such as pneumonia, brain swelling and even death, especially in young children who are not protected," said Dr. Regina Chinsio-Kwong, the county's health officer. "In recent years, approximately one in eight people diagnosed with measles in the U.S. have required hospitalization. Among children under 5, that number rises to one in five."
Symptoms include fever, cough, irritated teary eyes and a rash that usually starts on the head. The virus is highly contagious as it spreads through the air and from direct contact with those infected.
Contagiousness starts about four days before a rash and four days after it appears.
Anyone with symptoms is encouraged to call a doctor first before going out because it is so contagious.
Doctors say the best way to protect from measles is by getting a shot.
City News Service contributed to this report.