It could be all the surfaces need a good deep cleaning. Shampoo all fabric & carpet and wash down all the hard surfaces, cabinets, etc. I would indeed replace or sanitize your AC filters and clean up in all the duct work as well as possible. Then run all the ceiling vents wide open and some windows opened to completely air out the place until everything is dry.
If you still have odors...keep investigating...could be the sign there is something under the dash, in the vent system or even under the flooring that is causing problems.