China decided Thursday to lock down three cities that are home to more than 18 million people in an unprecedented effort to try to contain a deadly new viral illness that has sickened hundreds and spread to other cities and countries in the Lunar New Year travel rush. Police, SWAT teams and paramilitary troops guarded Wuhan’s train station, where metal barriers blocked the entrances at 10 a.m. Only travelers holding tickets for the last trains out were allowed to enter.

China decided Thursday to lock down three cities that are home to more than 18 million people in an unprecedented effort to try to contain a deadly new viral illness that has sickened hundreds and spread to other cities and countries in the Lunar New Year travel rush. Police, SWAT teams and paramilitary troops guarded Wuhan’s train station, where metal barriers blocked the entrances at 10 a.m. Only travelers holding tickets for the last trains out were allowed to enter.