At least eight people have been diagnosed with measles in an outbreak that started last month in the Philadelphia area. The most recent two cases were confirmed on Monday.

The outbreak began after a child who’d recently spent time in another country was admitted to the Children’s Hospital of Philadelphia (CHOP) with an infection, which was subsequently identified as measles. The Philadelphia Department of Public Health considers the case to be “imported” but did not say from where.

The disease then spread to three other people at CHOP, two of whom were already hospitalized there for other reasons.

Two of those infected at the hospital were a parent and child. The child had not been vaccinated and the parent was offered medication usually given to unvaccinated people that can prevent infection after exposure to measles, but refused it, the Philadelphia Inquirer first reported.

Despite quarantine instructions, the child was sent to day care on Dec. 20 and 21, the health department said.