The Indiana Department of Health reported Friday that Jennings County now has eight confirmed measles cases, up from a single case a week earlier. A day before that, one case was confirmed in Clark County, just across the Ohio River from Louisville.

Statewide, Indiana has recorded 134 confirmed measles cases, with at least 25 people requiring hospitalization.

In Kentucky, 11 cases have been identified across Washington, Carroll and Trimble counties, and the statewide total has surpassed 200 cases. Thirteen people have been hospitalized in Kentucky, according to the figures.

The numbers reflect a national resurgence of a disease that was declared eliminated in the United States in 2000. Measles is highly contagious and can spread through the air when an infected person coughs or sneezes; the virus can linger in a room for up to two hours after the person has left. It is especially dangerous for infants, pregnant people and those with weakened immune systems, and can cause pneumonia, brain swelling and death.

The Centers for Disease Control and Prevention says two doses of the measles-mumps-rubella vaccine are about 97 percent effective at preventing measles. But vaccination rates have slipped in many communities in recent years, leaving pockets of the population vulnerable to outbreaks.

Health officials in both states have urged residents to check their vaccination status and to contact a doctor if they suspect exposure. People who are not vaccinated and believe they may have been exposed should call ahead before visiting a clinic or emergency room so staff can take precautions to avoid spreading the virus to others.

The spread across county lines in Kentuckiana underscores how quickly the virus can move through under-vaccinated communities, and public health experts say the best protection remains timely vaccination.