Some 84 percent of deadly measles cases in a recent major outbreak at a migrant center in Chicago are linked to Venezuelan immigrants, a new CDC report shows.

New information reveals that the spate of 57 cases at the Pilsen migrant shelter can be traced back to a one year-old boy who had only received one of the two vital vaccines.

The majority of the cases — 72 percent — were among unvaccinated people, the CDC said.

The report cites overcrowding at the center for the rampant spread, with 500 people said to be crammed into a single room.