What is Haemophilus influenzae type b (Hib)?
What is Haemophilus influenzae type b (Hib)?
Hib is a bacterium that causes often-severe infections, particularly among infants. Before the introduction of effective vaccines, Hib was the leading cause of bacterial meningitis and other invasive bacterial disease, primarily among children younger than age 5 years.
Hib is an encapsulated strain of bacteria that colonizes the human nose and throat. The bacteria may spread throughout the body through the bloodstream and may become life threatening.1
What diseases are caused by Hib?
What diseases are caused by Hib?
The most common diseases resulting from Hib infection are meningitis, bacteremia, epiglottitis, arthritis, cellulitis, and pneumonia.
Osteomyelitis and pericarditis are less common forms of invasive disease.
Symptoms and Complications of Diseases Caused by Hib
| Meningitis | Meningitis, an infection of the membranes covering the brain and spinal cord, is the most common clinical manifestation of invasive Hib disease, accounting for 50% to 65% of cases in the prevaccine era. Hallmarks of meningitis are fever, decreased mental status, and stiff neck. Hearing impairment or other neurologic sequelae occur in 15% to 30% of survivors. The case fatality ratio is 3% to 6%, despite appropriate antimicrobial therapy. |
| Epiglottitis | Epiglottitis is an infection and swelling of the epiglottis, the tissue in the throat that covers and protects the larynx during swallowing. Epiglottitis may cause life-threatening airway obstruction. |
| Arthritis, Cellulitis, and Pneumonia | Septic arthritis, cellulitis, and pneumonia are common manifestations of invasive Hib disease. Osteomyelitis and pericarditis are less common forms of invasive disease.1 |
How is Hib transmitted?
How is Hib transmitted?
Hib colonizes the upper respiratory tract of humans and is transmitted person to person by inhalation of respiratory droplets or by direct contact with respiratory tract secretions. Neonates can acquire infection by aspiration of amniotic fluid or contact with genital tract secretions during delivery.1
What is the pathogenesis of Hib?
What is the pathogenesis of Hib?
The bacteria enter the body through the nasopharynx. Organisms colonize and may remain there for several months without symptoms. In some persons, Hib causes an invasive infection.1
How do you diagnose Hib disease?
How do you diagnose Hib disease?
A Gram stain of an infected body fluid may demonstrate small, gram-negative coccobacilli suggestive of Hib disease. CSF, blood, pleural fluid, joint fluid, and middle ear aspirates should be cultured on appropriate media. A positive culture for Hib establishes the diagnosis.
Detection of antigen or DNA may be used as an adjunct to culture, particularly in diagnosing Hib infection in patients who have been partially treated with antimicrobial agents, in which case the organism may not be viable on culture.1
What are the factors contributing to a higher risk of Hib?
What are the factors contributing to a higher risk of Hib?
Individual factors contributing to higher risk:1
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Age – youngest and oldest ages |
| Race/Ethnicity – Native Americans | |
| Chronic disease – functional and anatomic asplenia, human immunodeficiency virus [HIV] infection, immunoglobulin deficiency, complement deficiency, receipt of chemotherapy or stem cell transplant. |
Population factors contributing to higher risk:1
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CDC Disease Information
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CDC=Centers for Disease Control and Prevention; CSF=Cerebrospinal fluid;
Hib=Haemophilus influenzae type b.
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