<input type="checkbox" name="disease_id" value="1">A
<input type="checkbox" name="disease_id" value="2">B
<input type="checkbox" name="disease_id" value="3">C
<input type="checkbox" name="disease_id" value="4">D

var disease_id = "";
$('input:checkbox[name=disease_id]:checked').each(function(i){
    if(0==i){
        disease_id = $(this).val();
    }else{
        disease_id += (","+$(this).val());
    }
});

var res = 1,2,3,4;
var disease_id = res.split(",");
for(var i=0;i<disease_id.length;i++){
    $("input[name='disease_id']").each(function(){
        if($(this).val()==disease_id[i]){
            $(this).attr("checked","checked");
        }
    })
}