Infection of the skin is distinguished from dermatitis, which is inflammation of the skin, but a skin infection can result in skin inflammation. Skin inflammation due to skin infection is called infective dermatitis. Bacterial skin infections affected about 155 million people and cellulitis occurred in about 600 million people in 2013. Folliculitis is an infection of the hair follicle that can resemble pimples. Impetigo is a highly contagious bacterial skin infection most common among pre-school children. It is primarily caused by Staphylococcus aureus, and sometimes by Streptococcus pyogenes. Erysipelas is an acute streptococcus bacterial infection of the deep epidermis with lymphatic spread. Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters, burns, insect bites, surgical wounds, intravenous drug injection or sites of intravenous catheter insertion. Skin on the face or lower legs is most commonly affected by this infection, though cellulitis can occur on any part of the body. Fungal skin infections may present as either a superficial or deep infection of the skin, hair, and/or nails. As of 2010, they affect about one billion people globally.