Haemophilus influenzae, or H. influenzae, is a group of bacteria that cause different types of infections in infants and children. H. influenzae most commonly causes ear, eye, or sinus infections and pneumonia. In rare cases, your child may develop a more serious strain of the bacteria, called H. influenzae type b (Hib) infections. This type has been nearly abolished in the United States thanks to the Hib vaccine. H. influenzae infections spread from child to child by direct contact or through the air. The good news is that these infections can be successfully treated with antibiotics.