A Pierce County man in his 40s has been diagnosed with measles.

His illness was reported by authorities on May 12, one day after he developed a rash common among measles patients.

While it was unclear where the man was exposed to the measles virus, it reportedly occurred between April 19 and May 1. Exposures in the community as a result of this case occurred between May 6 and May 11, and additional cases of measles could occur between May 13 and May 31, according to the Tacoma-Pierce County Health Department.

Measles is contagious. It spreads through tiny droplets from the nose and mouth when an infected person coughs or sneezes, and other people then breathe in the droplets or touch contaminated surfaces and then their face.

People can’t get measles more than once, but for people who haven’t had the illness, complications are more common in children younger than 5 years old and adults older than 20. Officials say adults born after 1956 should have at least one dose of the MMR vaccine (measles, mumps and rubella); people born before 1957 are often immune, but should consider getting a dose of MMR.

Measles can be especially severe for people with weak immune systems.

Because of vaccines, measles is rare in the United States. But it is still common in some other countries, and non-immunized international travelers may bring measles to the U.S., Health Department officials said. High immunization levels are critical to prevent measles from spreading.