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Following the widespread adoption of routine childhood immunization against Haemophilus influenzae type b (Hib) in 1991, the rates of invasive Hib fell dramatically. In order to assure that surveillance was adequate to identify cases of Haemophilus influenzae type b (Hib) disease, Haemophilus influenzae invasive disease of all types (including b) was made reportable in late 2000. DOH now receives 4 to 13 reports of invasive H. influenzae of any type in children under 5 per year, with rare fatalities.

Purpose of Reporting and Surveillance

• To identify susceptible preschool-age children who may have been significantly exposed to a case of invasive H. influenzae.
• To educate potentially exposed persons about signs and symptoms of disease, thereby facilitating early diagnosis.
• To identify contacts and recommend preventive measures, including antibiotic prophylaxis and immunization.
• To identify situations of undervaccination or vaccine failure for cases of Hib.

Reporting Requirements

Cases of invasive disease due to H. influenzae of any type in children under age 5 are reportable according to the following requirements:

• Health care providers: immediately notifiable to Local Health Jurisdiction
• Hospitals: immediately notifiable to Local Health Jurisdiction
• Laboratories:  no requirements for reporting
• Local health jurisdictions:  notifiable to DOH Communicable Disease Epidemiology within 7 days of case investigation completion or summary information required within 21 days

Clinical Criteria for Diagnosis

Invasive disease caused by all types of Haemophilus influenzae may produce any of several clinical syndromes, including meningitis, bacteremia, epiglottitis, or pneumonia.  Reports are required only for cases occurring in individuals under five years of age and exclude otitis media.

• Isolation of H. influenzae of any type from a normally sterile site (e.g., blood or cerebrospinal fluid (CSF) or, less commonly, joint, pleural, or pericardial fluid).
  Note: Positive antigen test results from urine or serum samples are unreliable for diagnosis of H. influenzae disease.

Case Definition

• Probable: a clinically compatible case with detection of H. influenzae type b antigen in CSF.
• Confirmed: a clinically compatible case that is laboratory confirmed.

1. Identification

In the era before widespread use of Hib conjugate vaccines, Hib was the most common bacterial meningitis in children aged 2 months to 5 years in the US. It is usually associated with a bacteremia. The onset can be subacute but is usually sudden; symptoms include fever, vomiting, lethargy and meningeal irritation, with bulging fontanelle in infants or stiff neck and back in older children. Progressive stupor or coma is common. Occasionally, there is a low grade fever for several days, with more subtle CNS symptoms.

Diagnosis may be made by isolation of organisms from blood or CSF, or less commonly from other normally sterile sites. Specific capsular polysaccharide may be identified in CSF by CIE or LA techniques[ELC1].

2. Infectious Agent

H. influenzae are Gram-negative bacteria that are divided into unencapsulated (nontypeable) and encapsulated strains.  The encapsulated strains are further classified into serotypes a though f, based on the antigenic characteristics of their polysaccharide capsules.  Encapsulated H. influenzae can cause meningitis, epiglottitis, pneumonia, septic arthritis, cellulitis, pericarditis, empyema and osteomyelitis.  Hib is the most pathogenic. However, other serotypes can cause severe illness and even death. Nontypeable strains usually cause localized infections. 

3. Worldwide Occurrence

4. Reservoir

5. Modes of Transmission

6. Incubation Period

7. Period of Communicability

8. Susceptibility and Resistance

1. Preventive Measures

1. Routine childhood immunization for Hib. Several protein polysaccharide conjugate vaccines have been shown to prevent meningitis in children more than 2 months of age and are licensed in the US both individually and combined with other vaccines. Immunization is recommended starting at 2 months of age, followed by additional doses after 2 months; dosages vary with the vaccine in use. All vaccines require boosters at 12-15 months of age. Immunization is not routinely recommended for children more than 5 years of age.
2. Monitor for cases occurring in susceptible population settings, such as day care centers and large foster homes.
3. Educate parents about the risk of secondary cases in siblings less than 4 years old and the need for prompt evaluation and treatment if fever or stiff neck develops.

2. Control of Patient, Contacts and the Immediate Environment

1. Report to local health authority.
2. Isolation: Respiratory isolation for 24 hours after start of chemotherapy.
3. Concurrent disinfection: None.
4. Quarantine: None.
5. Protection of contacts (for serotype b only):
    

   • Careful observation of exposed unimmunized or incompletely immunized children who are household, child care, or nursery contacts of patients with invasive Hib disease is essential.  Exposed children in whom febrile illness develops should receive prompt medical evaluation.
      

   • Chemoprophylaxis:  The risk of invasive Hib disease is increased among unimmunized household contacts younger than 4 years of age. Rifampicin prophylaxis (orally once daily for 4 days in a 20 mg/kg dose, maximal dose 600 mg/day) for all household contacts (including adults) in households where there are one or more infants (other than the index case) less than 12 months of age or with a child 1-3 years of age who is inadequately immunized. When two or more cases of Hib invasive disease have occurred within 60 days and unimmunized or incompletely immunized children attend the child care facility, administration of Rifampicin to all attendees and supervisory personnel is indicated. When a single case of Hib has occurred, the use of Rifampicin  prophylaxis is controversial.

     The use of chemoprophylaxis for contacts of a case of invasive H. influenzae due to serotypes other than b is not recommended.
      

6. Investigation of contacts and source of infection: Observe contacts under 6 years old, and especially infants including those in household, day care centers and nurseries for signs of illness, especially fever.
7. Specific treatment: Ampicillin has been the drug of choice (parenteral 200-400 mg/kg/day). However, since about 30% of strains are now resistant due to beta-lactamase production, ceftriaxone, cefotaxime or chloramphenicol is recommended concurrently or singly until antibiotic sensitivities are known. The patient should be given rifampin prior to discharge from the hospital to assure elimination of the organism, if they received treatment with antibiotics other than cefotaxime or ceftriaxone.

3. Epidemic Measures

4. International Measures