Mycobacterium bovis (M. bovis) is a slow-growing (16 to 20 hour generation time) aerobic bacterium and the causative agent of tuberculosis in cattle. It is related to Mycobacterium tuberculosis, the bacterium which causes tuberculosis in humans. M. bovis can jump the species barrier and cause tuberculosis in humans and other mammals. M. bovis is usually transmitted to humans by consuming raw, infected cows' milk, although it can also spread via aerosol droplets. Actual infections in humans are nowadays rare in developed countries, mainly because pasteurisation kills M. bovis bacteria in infected milk. Bovine tuberculosis is a chronic infectious disease which affects a broad range of mammalian hosts, including humans, cattle, deer, llamas, pigs, domestic cats, wild carnivores (foxes, coyotes) and omnivores. It rarely affects equids or sheep. The disease can be transmitted in several ways. For example, it can be spread in exhaled air, sputum, urine, faeces, and pus, so the disease can be transmitted by direct contact, contact with the excreta of an infected animal, or inhalation of aerosols, depending on the species involved.