Japanese researchers at the Tokyo-based Nihon University have discovered that an acid produced in gum disease seems to accelerate the Human Immuno-deficiency Virus. Certain bacteria in periodontal or gum disease create a distinctively smelly substance called butyric acid. Butyric acid in turn inhibits an enzyme called HDAC that prevents HIV from reproducing. While not everyone with HIV gets periodontal disease, certain people are constitutionally prone to the disease. The study suggests that health-care workers should actively encourage all of their HIV+ patients to aggressively pursue their oral health habits including regular dental check-ups, daily brushing, and especially daily flossing to remove food debris that can promote the production of bacteria that produce the butyric acid. Butyric acid has an odor that has been likened to socks worn for several days or rancid butter.