Haemophilus sp cause numerous mild and serious infections,
including bacteremia, meningitis, pneumonia, otitis media,
cellulitis, and epiglottitis. Diagnosis is by culture and
serotyping. Treatment is with antibiotics. Many Haemophilus sp
are normal flora in the upper respiratory tract and rarely cause
illness. Pathogenic strains enter the upper respiratory tract
through droplet inhalation or direct contact. Spread is rapid in
nonimmune populations. Children, particularly males, blacks, and
Native Americans, are at highest risk of serious infection.
Overcrowded living conditions and day care center attendance
predispose to infection, as do immunodeficiency states,
asplenia, and sickle cell disease. There are several pathogenic
species of Haemophilus; the most common is H. influenzae, which
has 6 distinct encapsulated serotypes (a through f) and numerous
nonencapsulated, nontypeable strains. Before the use of H.
influenzae type b (Hib) conjugate vaccine, most cases of
serious, invasive disease were caused by t