Arthritis caused by bacteria, rickettsiae, mycoplasmas, viruses, fungi, or parasites; bacterial arthritis is frequently caused by staphylococcus aureus, streptococcus pneumoniae, haemophilus influenzae, borrelia, and neisseria gonorrhoeae; viral arthritis is less common than bacterial arthritis and may be a manifestation of such viral diseases as mumps, rubella, hepatitis, etc.