Cause: The bacterium Haemophilus influenzae (H. influenzae) has six known capsular serotypes (a-f) that can cause disease. Invasive disease occurs in normally sterile areas of the body, such as cerebrospinal fluid and bloodstream. H. influenzae type B (Hib) has been the most common type to cause invasive disease and the only one that is vaccine preventable. After the introduction of the Hib vaccine, cases of Hib disease decreased by 99%. As a result, non-vaccine serotypes, such as H. influenzae type a (Hia) and non-typeable strains (NTHi), have become a significant cause of invasive disease, particularly in young children, the elderly, and vulnerable populations.
Illness and treatment: Invasive H. influenzae symptoms can vary depending on the site of infection and may include meningitis, bacteremia, epiglottitis, pneumonia, or bone and joint infections. Meningitis is the most common form of invasive Hib disease. Typical symptoms of meningitis include fever, headache, stiff neck, vomiting, photophobia (sensitivity to light), and confusion. Common symptoms of bacteremia include fever, chills, and fatigue. Treatment includes antibiotics.
Sources: Humans, including asymptomatic carriers, are the only reservoir; the bacteria cannot live in the environment. Transmission is primarily person-to-person through inhaled respiratory droplets or by direct contact with respiratory tract secretions.
Additional risks: Unimmunized or underimmunized infants and children are at the highest risk for invasive H. influenzae type b disease. Rapid identification of invasive disease is necessary to ensure timely administration of chemoprophylaxis and Hib vaccine, as appropriate, to close contacts.
Prevention: Vaccination is the most effective way to prevent invasive H. influenzae type b infection in most children. Respiratory and hand hygiene help prevent transmission.
Purpose of Reporting and Surveillance
- To correctly identify the serotype of invasive Haemophilus influenzae (HI) organisms in children under 5 years old.
- To monitor the effectiveness of immunization programs and vaccines and to assess progress toward elimination of pediatric H. influenzae serotype B (Hib) invasive disease
- To identify children exposed to Hib cases and closely observe them for signs of illness
- To recommend antibiotic prophylaxis and/or immunization to appropriate contacts of Hib cases
- To identify additional cases and establish risk factors for cases of non-Hib invasive H. influenzae disease.
Legal Reporting Requirements
- Health care providers and health care facilities: immediately notifiable to local health jurisdiction; only invasive cases under 5 years old are reportable.
- Laboratories: immediately notifiable to local health jurisdiction; only cases under 5 years old are reportable; submission required – isolate or if no isolate available, specimen associated with positive result, within 2 business days (see Section 1C2).
- Local health jurisdictions: notifiable to the Washington State Department of Health (DOH) Communicable Disease Epidemiology (CDE) within 7 days of case investigation completion or summary information required within 21 days.