Infections of the nervous system caused by bacteria of the genus HAEMOPHILUS, and marked by prominent inflammation of the MENINGES. HAEMOPHILUS INFLUENZAE TYPE B is the most common causative organism. The condition primarily affects children under 6 years of age but may occur in adults. Infections of the nervous system caused by bacteria of the genus haemophilus, and marked by prominent inflammation of the meninges. haemophilus influenzae type B is the most common causative organism. The condition primarily affects children under 6 years of age but may occur in adults.