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close this bookWHO-Recommended Standards for Surveillance of Selected Vaccine-Preventable Diseases (WHO; 1999; 40 pages)
View the documentList of acronyms
View the documentIntroduction
View the documentDiphtheria
View the documentAcute viral hepatitis
View the documentHaemophilus influenzae type B (Hib) disease
View the documentMeasles
View the documentNeonatal tetanus
View the documentPertussis (whooping cough)
View the documentPoliomyelitis
View the documentRubella and Congenital Rubella Syndrome
View the documentYellow fever
View the documentAnnex 1 WHO Headquarters and Regional Office contacts
 

Haemophilus influenzae type B (Hib) disease

Rationale for surveillance

Hib is the most common cause of bacterial meningitis in children, and one of the two most common causes of severe bacterial pneumonia. Pneumonia is the largest single remaining infectious disease killer of young children in the developing world. Hib may also cause other diseases, including arthritis, skin infection, and epiglottitis. Surveillance data are critical for clarifying the burden of disease and evaluating the impact of immunization programmes. Although in many countries Hib pneumonia is more common than the other types of infection, diagnosis of Hib pneumonia is extremely difficult. Routine surveillance should focus on meningitis and other Hib infections, diagnosed with micro-biologic tests on blood, cerebrospinal fluid (CSF), and other body fluids (such as pleural fluid) that usually do not contain bacteria. Such infections are often called "invasive Hib disease". Countries may also wish to report potential cases of bacterial meningitis, both as a performance indicator for Hib detection, and to clarify the burden of meningitis attributable to all bacteria.

Recommended case definition

Clinical description

Bacterial meningitis is characterized by acute onset of fever, headache and stiff neck. Meningitis is not specific for Hib disease, and Hib disease cannot be diagnosed on clinical grounds.

Laboratory criteria for diagnosis

Culture method: isolation of Hib from a normally sterile clinical specimen, such as cerebrospinal fluid (CSF) or blood (i.e. culture of Hib from a non-sterile site, such as the throat, does not define Hib disease, since the bacteria can grow in these other areas and not cause disease). Antigen detection methods: identification of Hib antigen in normally sterile fluids (i.e. CSF or blood) by antigen detection methods such as latex agglutination or counter immunoelectrophoresis (CIE).

Case classification

Potential:

Bacterial meningitis case: a child with a clinical syndrome consistent with bacterial meningitis

Probable:

Not applicable

Confirmed:

A case that is laboratory confirmed by growing or identifying Hib in the CSF or blood

Note: Any person with Hib isolated from CSF or blood may be reported as a confirmed case, regardless of whether their clinical syndrome was meningitis.

Recommended types of surveillance

• Routine monthly reporting of aggregate data of confirmed cases is recommended from peripheral level to intermediate and central levels

• Zero reporting should be required at all levels

• All potential cases should also be reported if laboratory performance indicators are to be monitored (see Note)

Note: Since laboratory confirmation is required for all cases, the extent of surveillance will of necessity vary depending on the capabilities of individual countries. Surveillance does not need to be national in scope to fulfil goals as noted in "Rationale" section above. It is more important to have a well-functioning system in some areas than to have a national system that functions poorly.

Recommended minimum data elements

Aggregated data for reporting

• Number of cases
• Number of 3rd doses of Hib vaccine (Hib3) administered to infants

Case-based data for reporting and investigation

• Unique identifer

• Geographical area (e.g. district and province) names

• Date of birth

• Date of onset

• Specimen type, if specimen collected:

1 = blood; 2 = CSF; 3 = both; 4 = other

• Culture result, if done:

1 = positive; 2 = negative; 3 = pending; 4 = not done

• Antigen detection result, if done:

1 = positive; 2 = negative; 3 = pending; 4 = not done

• CSF white cell count/ml, if done

• Outcome:

1 = alive; 2 = dead; 9 = unknown

• Number of Hib doses received:

9 = unknown

• Final classification:

1 = potential; 2 = confirmed

Recommended data analyses, presentation, reports

Aggregated data

• Incidence rate by year and geographic area
• Hib3 coverage by year and geographic area
• Completeness and timeliness of reporting

Case-based data: Same as aggregate plus:

• Age-specific incidence rate

• Case fatality rate

• Cases by immunization status

Performance indicators of surveillance quality

Target

 

- Percent of all potential bacterial meningitis cases for which CSF/blood was obtained for evaluation

³ 90%

 

- Percent of potential bacterial meningitis cases in which a bacterial pathogen was identified from CSF or blood:

 
   

- Among CSF with 10 or more white blood cells/ml

³ 20%

   

- Among CSF with 100 or more white blood cells/ml

³ 50%

Note: Although persons with bacterial meningitis have a wide range of CSF white blood cell counts, the proportion of potential bacterial meningitis cases with identifiable bacterial causes increases with increasing CSF cell counts. For evaluation of performance, programme personnel may wish to determine proportion of potential bacterial meningitis cases in which bacterial causes have been identified in one or both of the above categories. Results below the target levels suggest some cases of bacterial meningitis are not being identified, and that review of laboratory and clinical practices should be performed.

Principle uses of data for decision-making

• To determine incidence of Hib meningitis and invasive disease for estimation of Hib disease burden
• To measure impact of immunization program and identify areas needing additional input
• To monitor coverage and take action to correct low coverage areas

Special aspects

Since Hib surveillance requires laboratory confirmation, nation-wide surveillance may not be practical in many countries. However, most surveillance goals may be approached with a less comprehensive plan. Surveillance in areas with appropriate clinical and laboratory capacity can provide necessary information on burden and immunization impact. Coverage data should be obtained nation-wide. Evaluating the combination of nation-wide coverage data, and area-specific disease data can provide necessary information for making immunization programme decisions. Additional guidance on surveillance methodology can be obtained in WHO publication WHO/VRD/GEN/95.05.

Contact information

Regional Offices and Headquarters (V&B)

See Annex 1 for addresses and fax numbers.

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