Two new measles exposure sites in the Portland metro area are now under investigation after confirmation of an additional case linked to recent regional transmission.

Health officials report that people who visited the two locations during specific time windows may have inhaled airborne measles virus, which can remain suspended in indoor air even after an infected person leaves. Measles is caused by a paramyxovirus and spreads mainly through respiratory droplets and aerosolized particles. Because of its high basic reproduction number, even brief, unprotected contact in shared air can lead to secondary cases among people without documented immunity.

Authorities are advising anyone who was at the identified sites and who lacks evidence of measles, mumps and rubella vaccination or laboratory-confirmed immunity to contact a healthcare provider. Clinicians are being asked to watch for fever, cough, coryza and conjunctivitis followed by a characteristic rash, and to implement airborne isolation protocols. Public health teams are conducting contact tracing and assessing community herd immunity to limit further transmission. Additional exposure locations may be added as the investigation continues.