e.g. find first .diseaseCon and clone it with only cloning the first .symptomCon too (actually I remove all .symptomCon but the first but that amounts to the same)
$('.diseaseCon').clone().find(".symptomCon:not(:first)").remove();
If you want to clone it and e.g. then append it to the body either use
$('.diseaseCon').clone().find(".symptomCon:not(:first)").remove().end().appendTo("body");
or
$('.diseaseCon').clone().appendTo("body").find(".symptomCon:not(:first)").remove();
Depending on the syntax you like more (where the first syntax should be faster as all operations are done on a fragment and only then the dom is modified
And you can replace :not(:first) with :gt(0) too. Or if you want to keep another symptom but the first use :not(:eq(X)) where X is the index of the symptom you want to keep