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A measles outbreak in northern Utah has spread to a county in the central part of the state, forcing a power plant there to turn away hundreds of employees.

A Millard County resident tested positive for measles late last week, the first confirmed case in the region in many years, say officials at the Central Utah Public Health Department.

The individual is believed to have caught the virus in Logan, where the person had traveled to get married, said agency spokeswoman Lisa Taylor. The case is likely connected to a measles outbreak in Cache County, which may or may not be linked to an outbreak that started this spring in the Salt Lake City area.

The Millard County individual worked at the Intermountain Power Agency plant in Delta, which has asked about 100 employees and contractors born after 1957 not to come to work until they can prove they have been fully vaccinated.

Some of the workers were able to find their records, while others could remain on paid leave for up to 21 days, said company spokesman John Ward.

The 500-person plant, which feeds power to Los Angeles and parts of southern Utah, expects no disruptions in operations, said Ward. "From an operational standpoint, this fits in the inconvenience category. People will have to shuffle schedules a bit, but we're still running."

Jennifer Brown, director of Utah's Bureau of Epidemiology, said local officials are working to contain the spread of the highly contagious disease, interviewing church, work and school contacts of anyone infected.

At last count, five individuals associated with the Cache County outbreak had been asked to isolate themselves. Those who have come in contact with the four and who haven't received two doses of the measles, mumps, rubella vaccine could be asked to quarantine themselves as well.

The vaccine is considered 99 percent effective after two doses.

"We strongly encourage individuals to stay up to date with their immunizations, as the MMR vaccine is one of the most highly effective vaccines given," said Bruce Costa, executive director of the Central Utah health department.

Measles causes fever, runny nose, cough and a rash. Nearly one-third of those who get the measles develop complications that can include meningitis, pneumonia, seizures, encephalitis, blindness and brain damage.