What is the morbidity and mortality associated with Haemophilus influenzae infections?

Updated: Jun 11, 2021
  • Author: Joseph Adrian L Buensalido, MD; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Overall mortality from Hib meningitis is approximately 5%. Morbidity rates from meningitis, however, are high. If subtle neurologic changes are included, as many as 50% of individuals with Hib meningitis have some neurologic sequelae, including partial-to-total sensorineural hearing loss, developmental delay, language delay, behavioral abnormalities, language disorders, impaired vision, mental retardation, motor problems, ataxia, seizures, and hydrocephalus. Approximately 6% of individuals with Hib meningitis experience permanent sensorineural hearing loss. Epiglottitis carries a mortality rate of 5-10% (because of acute respiratory tract obstruction), and neonatal H influenzae disease carries a mortality rate of 55%.

From the 1980s (prevaccine era) to 2005 (vaccine era), the incidence of vaccine-preventable invasive Hib disease decreased by ≥99.8%, and the associated mortality rate decreased by ≥99.5%. [23]

Licensing of the Hib conjugate vaccine led to a substantial decline of Hib disease in the United States. In parts of the world where the vaccine is not in regular use, morbidity and mortality rates of Hib disease remain high.

Epidemiologic studies suggest that Hia infection occurs more in indigenous North American populations, with clinical presentation closely resembling that of Hib infection. [25]

In 2006, the Active Bacterial Core Surveillance Report estimated that, in the United States, 4800 cases (1.6 per 100,000 population) of invasive H influenzae infection occurred, resulting in 700 deaths (0.23 per 100,000 population). [11] In contrast, the latest Active Bacterial Core Surveillance Report for H influenzae infection in 2015 reported 6,100 (1.9 per 100,000) cases of invasive disease and 1,015 (0.32 per 100,000) deaths. [12]

Bacteremia and invasive disease associated with NTHi are becoming more prevalent and carry a significant mortality rate. [11] Increased NTHi cases can also be seen in patients with cancer, consistent with the changing H influenzae epidemiology in the rest of the population after the Hib vaccine was introduced. [26]

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