If sneezing is the only symptom the cat displays, it is not necessarily due to an illness, reports PetMD. However, if the sneezing persists for several days or is accompanied by nasal or ocular discharge, it may indicate either a viral or bacterial infection of the upper respiratory tract.
Specific viral infections that can cause sneezing in cats include feline herpes virus, feline calicivirus, feline infectious peritonitis and feline immunodeficiency virus, notes WebMD. Bacterial infections that can cause sneezing include bordetella, mycoplasma and chlamydia. Finally, allergic reactions to pollutants, such as dust, pollen, mold and smoke, can cause sneezing in cats.