MTV News reported Friday that no details were given on Iero's condition or the nature of his illness. However, the band will soldier on with its tour.
The New Jersey group was in Tokyo this week, where they launched their first of four performances.
Iero, 25, will be replaced for the time being by Drive By guitarist Todd Price. The next stop on the tour is Down Under: first, New Zealand and from there, they'll head to Australia. A U.S. tour will launch on Feb. 22.