TUCSON - A measles patient was taken to University Medical Center's emergency room late last week, potentially infecting up to 500 people, according to authorities.
It's the 10th confirmed case of measles in Pima County since February when an infected woman from Switzerland visited the emergency room at Northwest Medical Center.
County Health Department officials don't believe the latest case is linked to the earlier cases and it remains undetermined how the boy contracted the disease.
The unidentified boy was taken to UMC on April 3 and soon was isolated.
Last week, health officials said they were concerned measles could be spreading through the community after they confirmed the third through ninth cases.
None of the five adults and five children stricken here had been vaccinated against measles, officials said.
Though it's now rare in the United States due to high childhood vaccination rates, the measles virus spreads easily through the air and is considered one of the most contagious of all infectious diseases.
In the worst cases, experts say measles can progress to pneumonia or encephalitis and can cause seizures, deafness and even death.