Guideline: Management, Prevention and Control of Meningococcal Disease in South Africa » Management of Outbreaks
 

13. MANAGEMENT OF OUTBREAKS

 

13.1 Managing outbreaks in an institution/organisation

 

13.1.1 First steps in investigation 

In educational settings, where a second case has occurred, the risk of a third case may be as high as 30-50%. A prompt investigation of all suspected clusters/outbreaks is essential. When two or more cases are reported from the same institution within a four week period, careful and rapid assessment should be made:

A site visit is recommended by the response team to:

  • Confirm the information available on cases
  • Ensure that all close contacts of cases have already received prophylaxis where indicated
  • Obtain copies of laboratory results and/or clinical notes and review these.
  • Obtain details on serogroup results if available from the RMPRU of the NICD (see contact numbers). If cases are different serogroups they should be managed as sporadic cases.
  • Make a line listing of suspected cases and classify them according to case definitions:

      - Confirmed

      - Probable

      - Possible

  • List the characteristics of the cases in terms of person, time and place.
  • A review of the epidemiological information on each case should be obtained and analysed. (See annexure A)
  • Cases should be classified according to definitions (see above) as:

      - Primary

      - Co-primary and

      - Secondary

  • The number of primary cases should be used to determine the attack rate within the institution. This requires information about the population at risk for use in the denominator. This is not always easily determined in an institution/organisation. The population at risk should make sense epidemiologically and have meaning for the people involved and this is used as the denominator
  • The case fatality rate (number of deaths over the total number of cases) should also be determined

* A primary case with its related co-primary and/or secondary cases is counted as only 1 case in calculating rates of meningococcal disease.

13.1.2 Options for control of institutional clusters/outbreaks 

The public health management options for an institutional outbreak may include:

  • No further action e.g.; if after thorough investigation only two possible cases are identified
  • Giving out information only
  • Giving out information and offering wider prophylaxis in the institution.

13.1.2.1 Role of chemoprophylaxis 

The main decision to be taken is whether to offer wider prophylaxis, and, if so, when and to whom. The evidence on risk suggests a need to act promptly. The target group for chemoprophylaxis should be a discrete group, for example, children and staff of the same preschool group, children of the same school year, children or students who share a common social activity, or a group of friends.

Some considerations in decision-making

  • If two possible cases attend the same institution, whatever the interval between

cases, prophylaxis – for any contacts – is not indicated.

  • If two confirmed cases exist but are caused by different serogroups of meningococcus, they should be regarded as two sporadic cases, whatever the interval between them. Only close contacts of each respective case should be offered chemoprophylaxis.
  • If a cluster/outbreak is confirmed in an institution (based on the criteria discussed above) and cases are from an identified subgroup e.g.; the same class, prophylaxis should be offered to that group.
  • If a cluster/outbreak is confirmed but is not confined to a well define subgroup, advice should be sought from the National Directorate: Communicable Disease Control (012 395 8096) or the NICD (011 386 6000/082 883 9920 - 24 hour Outbreak Hotline) regarding options for control.
  • During outbreaks, information should be given out widely within the institution as appropriate
  • For confirmed clusters/outbreaks among children at preschool groups and primary schools, staff should normally be included in the target group (there is some evidence of increased risk) but not usually in outbreaks among students at secondary schools, colleges, universities (here there is no evidence of increased risk amongst staff).
  • If unsure of the appropriate response always seek expert advice from National Directorate: Communicable Disease Control (012 395 8096) or the NICD (011 386 6000/082 883 9920 - 24 hour Outbreak Hotline).

13.1.2.2 Role of meningococcal vaccine in institutional outbreaks 

For a cluster involving two or more cases of confirmed serogroup group A, C, Y or W135 infections in an institution, quadrivalent polysaccharide vaccine may also be considered for all individuals over the age of two years who were given chemoprophylaxis in order to extend protection. For an outbreak involving a broader institutional community, vaccine is usually preferable, as mass chemoprophylaxis has not been shown to be effective in this setting.

13.1.2.3 Use of nasopharyngeal swabs during outbreaks Obtaining nasopharyngeal swabs for detection of carriage of outbreak strains is not recommended in acute outbreaks because decisions have to be taken before results are available and because carriage rates often bear no relationship to the risk of further cases. In addition a single negative swab does not exclude carriage.

NB: Closing an institution or school is not advised as no reduction in risks would be expected (levels of contact among social networks are unlikely to be reduced and may in fact be increased by closing an institution). Also the success of any intervention will be improved if school/institution attendance is high.

 

13.2 Managing outbreaks in the community

 

Identification of these outbreaks can be difficult and must be differentiated from an increase in sporadic disease. In order to do this, detailed epidemiological investigation of cases and calculation of attack rates is essential. In smaller populations, absolute numbers of cases rather than rates of disease may be more accurate. The calculation of age specific attack rates is useful to assess a potential target group for vaccination and the feasibility of such interventions.

Active case finding in the community should be commenced. An alert should be communicated to local general practitioners (GPs), paediatricians, out-of-hours services, clinics and hospitals with a clinical case definition in order to ensure all cases are identified, treated and reported promptly.

If it is established that an outbreak exists, decisions regarding appropriate intervention should be taken by the response team. Seek advice from national experts at the National Directorate: Communicable Disease Control (012 395 8042/8096) or the National Institute for Communicable Diseases (NICD): 011 386 6000/082 883 9920 (24 hour outbreak hotline).

One of the major challenges of interventions in community outbreaks is the difficulty in defining and reaching the target population. It is useful to try to define this group by population boundaries and age group. Such boundaries are often arbitrary but attempts should be made to use existing administrative boundaries e.g.: district, sub-district and/ or region that will make sense to the people who live in the area.

13.2.1 Role of chemoprophylaxis 

Community wide chemoprophylaxis is not recommended as it has not been shown to be of value. All close contacts of individual cases should be given prophylaxis as per the standard protocol.

13.2.2 Role of meningococcal vaccine 

This should be considered in community outbreaks due to serogroup A, C, Y or W135 depending on the serogroup, age group of affected population, geographic boundaries and feasibility. Such decisions should be made after careful assessment of all information by the full outbreak response team and in consultation with relevant experts.

13.2.3 Communications during outbreak 

An agreed public relations strategy is usually required, especially if high levels of interest are anticipated or already evident. This may include:

  • Telephone help-lines
  • Controlled media access to intervention sites
  • Regular coordinated press briefings and press conferences

 

13.3 Major meningococcal epidemics

 

Such a population wide epidemic has not occurred in southern Africa and seems unlikely in the foreseeable future. For an overview of recommendations of how major meningococcal epidemics should be managed see the Weekly Epidemiological Record 22 September 2000, No. 38, 2000, 75, 305–312. Available at http://www.who.int/wer and the Control of Communicable Disease Manual 18th ed. 2004. American Public Health Association.

 
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