Health officials issued the warning after tracing the infected rider's path across those counties. Measles spreads through the air and can linger in enclosed spaces long after an infected person leaves, which is why officials widened their search rather than focusing on one stop. Anyone who shared that train or those buses during the exposure window could be at risk, especially people who haven't gotten the MMR vaccine or don't know their vaccination status.
For riders in those counties, the message is simple. Watch for symptoms like fever, cough, or a rash in the days and weeks after possible exposure, and check with a doctor if anything shows up. Health officials rely on the vaccine to keep measles from turning one infected traveler into a wider outbreak. A single unvaccinated rider on public transit is enough to force six counties into monitoring mode.