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4. HAEMOPHILUS INFLUENZAE TYPE B INVASIVE INFECTION

Control Guideline

Last updated: 01 July 2012

1. Reason for surveillance

• To identify close contacts of the patient who may be at risk of developing Haemophilus influenza type b (Hib) invasive disease

• To monitor the epidemiology of Hib and so inform the development of better prevention strategies

• To identify cases of possible vaccine failure.

2. Case definition

A confirmed case requires laboratory definitive evidence only.

Laboratory evidence

• Isolation of Haemophilus influenzae type b (Hib) from a normally sterile site where typing has been confirmed at an approved reference laboratory, or

• Detection of Hib antigen in CSF when other laboratory parameters are consistent with meningitis.

Clinical evidence
Not applicable.

Epidemiological evidence
Not applicable.

3. Notification criteria and procedure

Haemophilus influenzae type b disease is to be notified by:

• Hospital CEOs on diagnosis (ideal reporting by telephone within 1 hour of diagnosis)

• Laboratories on culture or direct antigen confirmation (ideal reporting by telephone within 1 hour of diagnosis)

Only confirmed cases should be entered onto NCIMS.

4. The disease

Infectious agents
The Gram-negative bacillus Haemophilus influenzae serotype b.

Mode of transmission
Hib is transmitted by direct contact with respiratory droplets and discharges from the nose and throat of infected persons, including asymptomatic carriers.

Timeline
The typical incubation period is not clear, but is probably short, around 2 to 4 days. The infectious period lasts as long as organisms are present in the nasopharynx. Cases are probably most infectious in the 3 days before onset of symptoms. A case can be regarded as non-infectious after 24 hours of treatment with appropriate antimicrobial therapy.

Clinical presentation
Invasive Hib infections are uncommon in children <2 months (because of maternal antibodies) and >5 years old. Onset of symptoms is usually abrupt, and may include fever, headache, lethargy, anorexia, nausea, vomiting, and irritability. Progressive stupor or coma is common with meningitis. Children with epiglottitis usually demonstrate signs of upper respiratory tract obstruction and may have a characteristic expiratory snore.

5. Managing single notifications

Response times
Investigation
On same day of notification of a confirmed case begin follow-up investigation.

Within 10 working days of notification complete and return National Centre for Immunisation Research and Surveillance Hib Enhanced Surveillance Notification form to CDB for submission to NCIRS.

Data entry
Within 1 working day of notification enter confirmed cases on NCIMS.

Response procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up, PHU staff should ensure that action has been taken to:

• Confirm the onset date and symptoms of the illness

• Confirm results of relevant pathology tests, or recommend the tests be done

• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview

• Seek the doctor's permission to contact the case or relevant care-giver

• Ensure that contacts are identified and protected

• Collect clinical and epidemiological and laboratory data as per the Hib enhanced notification form

• Obtain details and documentation of previous Hib immunisation, if any (date and batch number).

Case management
Investigation and treatment
Patients suspected to have invasive Hib disease requires immediate treatment. Refer to the current Therapeutic Guidelines: Antibiotic for treatment. If treatment did not include a third generation cephalosporin, the patient should also be given a course of rifampicin to eliminate nasal carriage. The dosage of rifampicin is 20 mg/kg up to a maximum of 600mg once daily for 4 days, or 10 mg/kg per day for infants <1 month old. It is important to note that this dosage is different to that recommended for meningococcal infections.

The possible side effects and drug interactions of rifampicin should be explained:

• Gastrointestinal upset, headache, dizziness and drowsiness commonly occur

• Rifamipicin stains body fluids such as urine, sweat and tears an orange colour. Soft contact lenses should not be worn until the urine has returned to its normal colour, as they become stained

• Women who are taking the oral contraceptive pill should use additional contraceptive for the cycle during which they are taking rifampicin

• Rifampicin should not be taken by pregnant women, or by persons with liver disease

• Rifampicin interferes with the metabolism of chloramphenicol. If chloramphenicol is used for treatment, rifampicin prophylaxis should commence once the chloramphenicol is ceased

• Rifampicin interferes with the metabolism of other drugs including anticoagulants, digitalis, corticosteroids, cyclosporin, oral hypoglycaemics, phenytoin, theophylline and quinidine.

PHU's should ensure that clinical isolates are referred by the laboratory to ICPMR for typing.

Education
The case or relevant caregiver should be informed about the nature of the infection and the mode of transmission. In particular, emphasis should be placed on minimising the exposure of susceptible persons to the infectious patient.

Isolation and restriction
Exclude cases from school, preschool, childcare or other settings where there are susceptible individuals, especially young children and infants until completion of treatment and completion of ≥24 hours of appropriate prophylaxis.

When Hib is suspected, hospitalised cases should be cared for with droplet precautions until ≥24 hours after initiation of antibiotic therapy.

Environmental evaluation
None

Contact management
Identification of contacts
Household contacts are persons residing with the index case or others who spent 4 or more hours with the index case, for at least 5 of the 7 days proceeding the day of hospital admission of the index case.

Household contacts (of any age) are more likely to carry Hib, and there is an increased risk of invasive Hib disease in unvaccinated household contacts <4 years old. Rifampicin is 95% effective in eradicating Hib carriage, and probably also decreases the risk of secondary cases. For childcare contacts, the risk of disease is lower than among household contacts, and is rare when all contacts are >2 years old. The efficacy of rifampicin in preventing disease in childcare groups is not well established.

Because of the high efficacy of Hib vaccine, rifampicin is not indicated when all household or child care contacts aged <48 months have been completely immunised ≥14 days before onset of the case (i.e. ≥1 dose at 15 months or older, 2 doses between 12 and 14 months, or 2-3 doses when <12 months with a booster at 12 months or older). Note that children <12 months old will not be completely immunised. Where an immunocompromised child is in the household, regardless of immunisation status, all members should receive rifampicin.

Direct contact with respiratory secretions from the case is generally considered significant. Health care workers who have not had direct contact with the case's nasopharyngeal secretions are NOT at risk and prophylaxis is not recommended for them.

Chemoprophylaxis is recommended for:

• All household contacts (except pregnant women), irrespective of age, with at least 1 contact younger than 4 years of age who is unimmunised or incompletely immunised. The index patient also should receive chemoprophylaxis

• All members of a household with a child younger than 12 months of age, even if the primary series has been given

• All occupants of a household with an immunocompromised child, irrespective of the child's Hib immunisation status

• Nursery and child care centre contacts, irrespective of age, when 2 or more cases of invasive disease have occurred within 60 days

• Index case, if treated with regimens other than cefotaxime or ceftriaxone. Chemoprophylaxis usually is provided just before discharge.

Chemoprophylaxis is not recommended for:

• Occupants of households with no children younger than 4 years of age other than the index patient

• Occupants of households when all household contacts younger than 48 months of age have completed their Hib immunisation series

• Childcare centre contacts of a single index case, especially those older than 24 months of age. See management for special situations

• Pregnant women.

Treatment
Passive immunisation
None.

Active immunisation
Hib vaccine is routinely recommended for children <5 years old. Because of the length of time necessary to develop antibodies, vaccination does not play a major role in the management of patients with Hib disease or their contacts. There is evidence that conjugate Hib vaccines reduce oropharyngeal carriage of Hib in vaccinated children and therefore indirectly protect unvaccinated children.

Antibiotic prophylaxis
Rifampicin should be recommended for contacts as defined above in a dose of 20 mg/kg up to a maximum of 600mg once daily for 4 days, or 10 mg/kg per day for infants <1 month. This regime is different to that recommended for meningococcal infections. Treatment should be initiated within 7 days of first contact, but may still be beneficial if given up to 30 after contact.

Local health districts should ensure that rifampicin is readily available to all contacts providing it free when necessary.

Because of its unknown effect on foetuses, pregnant women should not be offered rifampicin prophylaxis.

Although data are limited, if rifampicin is considered unsuitable (e.g. pregnant women), ceftriaxone 1g (children: 50mg/kg up to 1g) intravenously or intramuscularly, daily for 2 days. may be used as prophylaxis.

Note that the index case does not require prophylaxis therapy if given ceftriaxone.

Education
Advise susceptible contacts (or parents/guardians) of the risk of infection; counsel them to watch for signs or symptoms of Hib occurring within 14 days of exposure. Any suspicion of Hib disease should signal the need for immediate medical attention. These persons should be warned that the risk may persist for 14 days for household contacts and for up to 60 days for child care contacts.

Isolation and restriction
Contacts receiving rifampicin may continue to attend school, preschool or childcare.

6. Managing Special Situations

Cases among children in child care settings
If the case has attended a childcare centre in the 7 days before onset, seek further information. In addition to routine case investigation, it is important to emphasise to parents and directors of childcare facilities the need to observe children carefully and to report any new diagnoses of Hib disease immediately. Information should be sought about other children with meningitis or epiglottitis who attended the centre within the previous 60 days.

Parents and staff should be provided with information about the disease and its prevention. Written information such as a fact sheet is recommended, but an information meeting for parents may also be useful.

Where a single case has occurred in a child care centre, the following should be considered:

• Case attends child care with incompleted vaccinated children aged ≤ 24 months for 4 hours or more per day for at least 5 to 7 days preceding the day of hospital admission of the index case: rifampicin should be given to all children and staff who share the same indoor area, regardless of immunisation status. (For single cases in a child care setting, if all contacts are >24 months old, rifampicin prophylaxis need not be given, regardless of vaccination status.)

• >1 case has occurred in a child care facility within a 60-day period and incompletely vaccinated children attend: rifampicin should be offered to all children and staff.

Children and staff in other rooms are usually not at elevated risk and do not require prophylaxis.

The child care centre director should strongly encourage all children entering child care for ≥2 months after onset of the case to be age-appropriately immunised.

Multiple cases in a defined population
If 2 or more cases occur within 60 days of each other in a discrete population such as a childcare centre or another institution, notify Communicable Diseases Branch.