Last Saturday during practice, Jönsson was rushed to the hospital with a strained groin muscle. That type of injury can take up to several weeks to fully heal and Jönsson is not going to be fit enough to race in the championships.
It is a particularly tough blow for Jönsson because the competition is being held in Sweden.
Carl Quicklund will race instead of Jönsson. The World Ski Championship takes place in Falun and receives its official opening on Wednesday evening.
There has been criticism of the spiralling cost of staging the championships in Falun.