It's not so much as it laying dorment as much as someone may not even know they have it.
Chlamydia is known as a "silent" disease because about three quarters of infected women and about half of infected men have no symptoms. If symptoms do occur, they usually appear within 1 to 3 weeks after exposure.
Under-reporting is substantial because most people with chlamydia are not aware of their infections and do not seek testing. Also, testing is not often done if patients are treated for their symptoms.
You can read more here.
http://www.cdc.gov/std/Chlamydia/STDFact-Chlamydia.htm#HowGet
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