Bacterial meningitis and septicaemia are caused by the Neisseria meningitidis (meningococcus), Streptococcus pneumoniae (pneumococcus) and Haemophilus influenzae type b (Hib) and can occur singly or more commonly together, when they are known as meningococcal disease. Bacterial meningitis occurs when the bacteria, which is found normally in the upper respiratory tract, infect the lining of the brain (meninges) and the spinal cord. Meningococcal septicaemia is caused when the bacteria multiply rapidly in the bloodstream, leading to damage to blood vessels and, in some cases, multi-organ failure or damage.