Database
[{"caseCount":28},{"caseCount":35},{"caseCount":23},{"caseCount":28},{"caseCount":24},{"caseCount":39},{"caseCount":20},{"caseCount":29},{"caseCount":38},{"caseCount":40},{"caseCount":33},{"caseCount":40},{"caseCount":31},{"caseCount":20},{"caseCount":33},{"caseCount":28},{"caseCount":23},{"caseCount":28},{"caseCount":28},{"caseCount":30},{"caseCount":29},{"caseCount":25},{"caseCount":31},{"caseCount":28},{"caseCount":38},{"caseCount":37},{"caseCount":39},{"caseCount":25},{"caseCount":30},{"caseCount":33},{"caseCount":39},{"caseCount":33},{"caseCount":27},{"caseCount":20},{"caseCount":32},{"caseCount":38},{"caseCount":20},{"caseCount":35},{"caseCount":34},{"caseCount":21},{"caseCount":37}]
Query
db.collection.aggregate({$group:{_id:null,toatalCaseCount:{$sum:"$caseCount"}}})