How to create shape file for the no of cases are per county which are joined with the county map from from TIGER.
I don't fully understand the question, which data types are you joining? If it's a spatial join you will need to save the displayed data into a gis format first, right click on the displayed data in the TOC and go to data->export data
What you need to do is add the join to the shapefile table, not your csv. The attributes of the matching records from your csv will be transferred to the attribute table of the counties shapefile. Because a join is temporary in nature, you will then have to export the shapefile to a new one (right click on the the shapefile in the table of contents, data->exportdata).