A measles outbreak in the U.S. continues to expand as Oklahoma joins the growing list of states to report cases of the highly-infectious disease.

The Oklahoma State Department of Health announced two cases of measles have been detected in the state. Health officials said the cases likely stemmed from larger outbreaks in bordering Texas and New Mexico.

According to the U.S. Centers for Disease Control and Prevention, cases have also been reported in Alaska, California, Florida, Georgia, Kentucky, New Jersey, New York, Pennsylvania, Rhode Island, and Washington

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"These cases highlight the importance of being aware of measles activity as people travel or host visitors,” Kendra Dougherty, Director of Infectious Disease Prevention and Response at OSDH said in a statement. “When people know they have exposure risk and do not have immunity to measles, they can exclude themselves from public settings for the recommended duration to eliminate the risk of transmission in their community.”

According to most recent data published Friday by the CDC, more than 200 cases of measles have been reported this year in the U.S., including two people who have died that were unvaccinated. The CDC said about a third of those cases have been in children under the age of five, and 17% of cases have required hospitalization.

The worst of the outbreaks is in the South Plains region of Texas where health officials tell Scripps News the disease is primarily impacting a Mennonite community. The Texas Department of State Health Services said Tuesday 223 cases of measles have been reported in the state this year.

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Health officials, meanwhile, are warning that additional cases are likely, citing the highly contagious nature of the measles virus. Earlier this month, Health and Human Services Secretary Robert F. Kennedy Jr. called the measles outbreak a "call to action" and said getting vaccinated is "crucial" in combating the disease.

"As healthcare providers, community leaders, and policymakers, we have a shared responsibility to protect public health," he wrote in a Fox News op-ed. "This includes ensuring that accurate information about vaccine safety and efficacy is disseminated. We must engage with communities to understand their concerns, provide culturally competent education, and make vaccines readily accessible for all those who want them."

According to the CDC, symptoms of measles typically begin with a high fever, cough, runny nose, and watery eyes. Two to three days after these initial symptoms, tiny white spots may appear inside the mouth.