The Greek crisis festered and spread to other deficit countries.
Taken here To fester
v.intr.
1. To generate pus; suppurate.
2. To form an ulcer.
3. To undergo decay; rot.
4.
a. To be or become an increasing source of irritation or poisoning; rankle: bitterness that festered and grew.
b. To be subject to or exist in a condition of decline: allowed the once beautiful park to fester.
v.tr.
To infect, inflame, or corrupt.
n.
A small festering sore or ulcer; a pustule.
Explanation and further comments are
here. BTW Interesting Soros' sketch. Follow link at the top of the post.