Haemophilus is a genus of bacteria that includes several species, some of which can cause infections in humans. These bacteria are typically found in the respiratory tract and can lead to illnesses such as pneumonia, meningitis, and ear infections. One well-known species is Haemophilus influenzae, which is often associated with severe respiratory diseases. These bacteria are small, non-motile, and require specific nutrients to grow, making them fastidious organisms. Vaccines are available to protect against certain strains, particularly Haemophilus influenzae type b (Hib), which has significantly reduced the incidence of related diseases in children since its introduction.