Multnomah County officials say approximately 500 people were exposed to a confirmed case of measles in the Portland area Wednesday.

Of those 500 people, the Multnomah County Health Department Communicable Disease Services team is monitoring 40 people who were exposed and considered non-immune.

So far, no other cases have been identified.

Measles is an illness caused by a virus. It is spread through the air by coughing and sneezing and is highly contagious.

People with measles can spread the virus to others before they show symptoms. The virus can also linger in the air for minutes or hours after someone with measles leaves the area.

“Measles is a serious disease that was basically eliminated in the United States thanks to routine childhood vaccination,’’ said Dr. Jennifer Vines, Multnomah County Deputy Health Officer. “When we see measles today, it is rare and usually the result of a person who was unknowingly infected while traveling outside the United States.”

Officials say the infected person visited a local emergency room and spent time in a Gresham childcare center.

They say anyone who was infected from the person will begin to show symptoms by mid-July at the latest.

The people with the greatest risk of catching measles are those who are not vaccinated, pregnant women, infants under 12 months and people with weakened immune systems.

A person is considered immune to measles if they were born before 1957, had the measles previously, or have been fully vaccinated for measles.

Measles symptoms start with a fever, cough, runny nose and red eyes followed by a red rash that usually begins at the head and spreads to the rest of the body. People are contagious with measles for four days before the rash appears and up to four days after the rash appears.

Read the full article.