A composite filter media structure and an associated method of making are provided. The structure includes a base substrate that includes a nonwoven fabric substrate formed from a plurality of bicomponent synthetic fibers using a spunbond process. The composite filter media structure includes a nanofiber layer deposited on one side of the base substrate by an electro-blown spinning process. In one aspect, the base substrate and the nanofiber layer are configured to provide at least an 85% filtration efficiency measured in accordance with an ASHRAE 52.2-1999 test method. In another aspect, the nanofiber layer has a basis weight of about 2.0 g/m2 to about 3.0 g/m2.