H. influenzae has a variety of symptoms some of which may depend on the presence of the bacterial capsule. Until the availability of the Hib vaccine, the type-b H. influenzae was the main cause of meningitis in children between 6 months and 5 years, although older children, adolescents and adults can also be infected.
At first the infection causes a runny nose, low grade fever and headache (1-3 days). Due to the invasive nature of the organism ,it enters the circulation and crosses the blood-brain barrier, resulting in a rapidly progressing meningitis (stiff neck), convulsions, coma and death. Timely treatment may prevent coma and death, but the patient may still suffer from deafness and mental retardation.
Type-b H. influenzae may also cause septic arthritis conjunctivitis, cellulitis, and epiglottitis, the latter results in the obstruction of the upper airway and suffocation. H. influenzae of other types may rarely cause some of the symptoms listed above.
A significant cause of genital ulcers (chancroid) in Asia and Africa but, is seen less commonly in the USA. The incidence is approximately 4000-5000 per year with clusters found in California, Florida, Georgia and New York.
The infection is asymptomatic in women but about a week following sexual transmission to a man, it causes appearance of a tender papule with erythematous base on the genitalia or the peripheral area. The lesion progresses to become a painful ulcer with inguinal lymphadenopathy. The H. ducreyi lesion (chancroid) is distinguished from a syphilitic lesion (chancre) in that it is a comparatively soft lesion.
Haemophilus influenzae aegyptius
This bacterium, previously known as H. aegyptius, causes an opportunistic organism which can result in a fulminant pediatric disease (Brazilian purpuric fever) characterized by an initial conjunctivitis, followed by an acute onset of fever, accompanied by vomiting and abdominal pain. Subsequently, the patient develops petechiae, purpura, shock and may face death. The pathogenesis of this infection is poorly understood. The growth conditions for this organism are the same as those for H. influenzae.