ACTERIAL MENINGITIS MAKES A COMEBACK

R ecent reports from interstate and overseas haveraised concerns about a resurgence of bacterial

meningitis. In Victoria in 1989 there were 65 notifiedcases of meningococcal meningitis, with three deaths.This represented a threefold increase over theprevious year. Outbreaks of meningococcalmeningitis have been reported recently fromVictoria Northern Territoryz and Western AustraliaS.

Although meningococcal infection is notifiablein NSW, septicaemia and meningitis are notdifferentiated. Meningitis due to Haemophilusinfluenzae is not notifiable.

In May 1990 reports of two clusters of bacterialmeningitis from the North Coast and the NewEngland Regions prompted the following epidemiologicinvestigation of bacterial meningitis in NSWThe aims of the study were twofold:

to determine the true incidence of bacterialmeningitis in NSW.to assess the characteristics of threesurveillance systems specifically formeningococcal meningitis: the existinginfectious diseases notification system, activesurveillance by Medical Officers of Health(MOHs), and the NSW Health DepartmentInpatient Statistics Collection (ISC).

All separations from NSW hospitals are reportedto the Health Department ISC. Specific conditionsare coded according to ICD9-CM. We used this datasource to identify hospital patients discharged fromhospital between July 1, 1988 and June 30, 1990with a diagnosis of bacterial meningitis (ICD9-CM320) and meningococcal infection (ICD9-CM 036),assuming that people with these conditions wouldbe admitted to public hospitals. We excluded recordswith a discharge diagnosis of neonatal meningitis orpost-craniotomy meningitis as these conditions arenot notifiable. Patients transferred between hospitalswere counted according to the hospital of firstadmission. We attributed data from a hospital withinany Area/Region to that Area Health ServicelRegion.No attempt was made to assess admission patternsacross 5borders'.

Passive survefflance of infectious diseases occursthrough medical practitioners notifying theDepartment of scheduled medical conditions.Although notification of meningococcal infectionsis required under the Public Health Act, we believecompliance with these provisions has been poor.

We initiated Statewide active surveillance ofbacterial meningitis for the period January 1 to May22, 1990 by asking MOHs from all 16 Health Areasand Regions to obtain details on all people admittedto hospitals with a primary diagnosis of bacterialmeningitis or meningococcal disease. We requesteddata on age, sex, specific diagnosis, Aboriginality,date of hospital admission, date of separation anddischarge status.

REPORTED MENINGOCOCCALINFECTIONS IN NSW, 1982-1990

1982 121983 301984 181985 211986 121987 231988 181989 58

1990 84

BACTERIAL MENINGITIS IN NSW,JAN 1-MAY 22, 1990.BY AREA HEALTH SERVICEIREGIO NOF NOTIFICATION

Frequency 1OOOOORate Population/Year

Area Health ServiceCentral Sydney 4 3.1Eastern Sydney 1 0.8Northern Sydney 6 2.1Southern Sydney 3 1.5South WestSydney 8 3.4Western Sector** 9 2.7Central Coast 3 3.6Hunter II 5.9

Illawarra 0 0.0

RegionNorth Coast 11 8.3New England 6 6.3Orana&Far West 3 5.5Central West 0 0.0

South East 1 1.4South West 7 7.2

Total 73

** Combined Western Sydney and Wentworth Area Health Services

As the active surveillance period was for 142 days,we computed annual incidence rates by multiplyingrates by a factor of 365/142. No attempt was madeto interpret the non-linear distribution of bacterialmeningitis with regard to seasonality.

The Chandra Sekar and Deming (C SD) methodprovides an estimate of cases not identified by eitherof two independent surveillance programs4. We usedthis method to determine the number of cases notidentified by the passive notification systems or theMOH-initiated active surveillance system.

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RE5 ULTSIncidence of bacterial meningitisIn NSW from July 1, 1988 to June 30, 1989 therewere 309 admissions for bacterial meningitis for arate of 5.41100,000 population5. Of these, 71 were formeningococcal meningitis - a rate of 1.2/100,000.Among children less than five years of age there were35 admissions for meningococcal meningitis and163 for other bacterial meningitis.

Between July 1, 1989 and June 30, 1990 there were289 admissions for bacterial meningitis for a rateof 5.1/100,000 population. Of these admissions,80 were for meningococcal meningitis - a rateof 1.4/100,000.

Surveillance of meningococcal meningitisThe NSW infectious diseases database recorded thefollowing numbers of notifications of meningococcalinfections for 1982-90 (Table 1):

For January 1 to May 22, 1990 medical practitionersnotified 14 patients with meningococcal infectionthrough the existing infectious disease notificationsystem.

All Health Areas and Regions responded to therequest for hospital data. Active surveillance bythe MOHs between January 1 and May 22 revealed73 patients with bacterial meningitis. Of these,30 were meningococcal (Tables 2, 3). Aboriginalitywas coded in only 11 per cent of records. Fifty-sevenper cent of cases of meningococcal meningitis occurredin children under five years of age and of these, 88 percent were aged less than two years (Table 4).

We could not link two patients notified by medicalpractitioners with patients detected through theactive surveillance program. Using the CSD methodwe estimate that three patients with meningitis werenot detected through either the active or the existingpassive surveillance (Table 5).

The ISC identified 89 cases of bacterial meningitisfor the surveillance period - 26 with meningococcalmeningitis.

DISCUSSIONThe incidence of bacterial meningitisIn NSW the incidence of bacterial meningitis was5.4/100,000 for 1988/89 and 5.1/100,000 for 1989/90. Therate for meningococcal meningitis for children underfive years of age was calculated at 10.5/100,000. Therate for H influenzae meningitis for children under fivewas calculated at 13.6/100,000. These rates are all lowerthan similar rates in interstate and overseas reports.

Rates for the generic grouping 'bacterial meningitis'have been reported in a Scottish study as16.9-17.8/100,000. And in a recent article, caseattack rates of 10-35/100,000 are reported forepidemic periods of meningococcal disease in Australia1.

Reported age-specific rates for H influenzaemeningitis in under five-year-olds for the UnitedStates are 75-150/100,000 and for Victoria,58.5/100,0008.

There is seasonal variation in the incidence ofmeningococcal meningitis. Reported US experiencenoted that the highest incidence for bacterialmeningitis occurs in winter and spring, with sporadiccases reported throughout the year9. In Victoria thepeak incidence occurs in August and September,and the lowest incidence is in March and April7.

As the active surveillance period corresponds to atrough period, extrapolation from our survey wouldunderestimate the annual incidence in NSW (Table 2).

Survefflance of bacterial meningitisAs only meningococcal meningitis is notifiable,comparison of the three surveillance systems ispossible using this specific diagnosis as the indexcondition. Routine notification revealed 14 cases,active surveillance 30, and hospital morbidity data26. Extrapolation using CSD suggests a total of35 cases of meningococcal meningitis during thesurveillance period.

The discrepancy between the estimated 35 cases andthose reported through surveillance mechanismsmay be explained partly by the wide spectrum ofclinical manifestations of this condition. Fulminantmeningitis may cause death before hospitaladmission. Blood infection with meningococcus canoccur with or without meningitis; the diagnosis ofmeningitis may be missed by clinicians10.

The existing notification systemNotification rates for bacterial meningitis haveincreased in 1989 and 1990, compared with the years1982-1988 (Table 1), yet these rates are still lowerthan those reported in interstate and overseasstudies

Meningococcal disease is notifiable by medicalpractitioners in NSW. Proposals for infectious diseasenotifications recommend that meningococcal diseasecontinue to be notifiable with specification ofsepticaemia or meningitis; that Haemophilus

•f:] 1*

PERCENT DISTRIBUTION OF PATIENTSWITH BACTERIAL MENINGITIS BYCAUSAL ORGANISM REPORTED BYMOHo. NSW JAN 1-MAY 22,1990

Organism No Per cent

Neisseria meningitidis 30 41.1Haemophilus influenzae B 22 30.1Streptococcus pneumoriiae 12 16.4Listeria monocytogenes 4 5.5Staphylococcus aureus 3 4.1Bacillus sp. 1 1.4Klebsiela pneumoniae 1 1.4

Total 73 100.0

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REPORTED BACTERIAL MENINGiTISLN CHILDREN AGED LESS THANFIVE YEARS, NSW, JAN 1-MAY 22, 1990

Organism AgeUnder 2 2-4 yrs

Neisseria meningitidi5 15 2Haemophilus influenzae B 19 3Streptococcus pneumoniae 9 2Bacillus sp. 1 0

Total 44 7

PATIENTS REPORTED WITHMENINGOCOCCAL MENINGiTISDETECTED BY SURVEILLANCEMETHOD, NSW, JAN 1-MAY 22, 1990

Cases detected by active surveillanceYes No

Present Yes 12 2 14notificationsystem No 18 3* 21

30 5 35

* Estinisted by (SD rrethod

influenzae B meningitis, septicaemia and epiglottitisbecome specifically notifiable; and that other formsof bacterial meningitis remain non-.notifiable. Bothlaboratories and Chief Executive Officers/RegionalDirectors (or their delegate) would be asked to notifythese cnditins.

Active surveillance by MOHsUsing ISC as the 'gold standard', the sensitivityof active notification was 82 per cent (7 3/89).

The active surveillance project provided the mostaccurate information in terms of identifying cases ina timely manner. But the study was labour-intensiveand therefore not ideal as a routine surveillance method.

Inpatient Statistics CollectionThe ISC has no place to play in monitoring outbreaksof bacterial meningitis - cases are registered only onseparation, not admission. Even if ISC were available'on-line' Public Health Units would be alerted to anoutbreak of meningitis only when treatment hadbeen completed.

The discrepancy between the cases of meningococcalmeningitis identified by MOHs (30) and those by theISC (26) may be because MOH cases were admissions,while ISC reports on separations. Cases may havebeen admitted within the surveillance period butdischarged after June 30, 1990, when the presentcollection was closed.

The poor coding of Aboriginality precludes analysisof this variable. It is the experience of the NSWHospital Morbidity Collection that Aboriginalityis coded in no more than 33 per cent of records(P Williams, personal communication). There is reasonto believe the epidemiology of bacterial meningitisdiffers among Aborigines and non-Aborigines2.

The utility of hospital separation data is limitedby delays of more than four months between close ofcollection period and availability of the information.

RECOMMENDATIONSPHU staff hou1d develop improved surveillancestrategies for detecting meningitis throughbetter communication between Unit staffand health professionals in the Area HealthService/Region. Medical officers in hospitalscould notify all cases of bacterial meningitisby telephone to the MOH for their AreaHealth Service/Region to initiate contacttracing and assess the need for prophylacticantibiotics.PHUs should investigate reasons for medicalpractitioners failing to notify meningitis.Where specific cases are identified throughactive surveillance or ISC, the treatingpractitioner would be contacted by the PHUstaff, asked to submit a formal notificationand asked the reasons for non-notification.Epidemiology Branch should use ISC datato monitor the completeness of doctor- andlaboratory-based notifications of meningitis.Laboratories should be asked to include thesubtype of N. meningitidis with theirnotifications. This is important to motivatethe appropriate public health response; themeningococcal vaccine currently availableis not recommended for use against type B7.

Michael Leu Wendy Manning, George Rub inEpidemiology and Health Services Evaluation BranchNSW Health Department

1. Clements DA, Gilbert L. Increase in meningocoocal infectionsdetected at the Royal Children's Hospital, Melbourne. CommunicableDiseases lntelhgence 1990;8:4-7.2. Meningococcal meningitis, Victoria and Central Australia.Communicable Diseases intelligence 1989;21 :3-4.3. Watson C, Gardner V. A cluster of cases of group C meningococcalinfection in Katanning, Western Australia. Communicable Diseasesintelligence 1990;5:4-6.4. Shryock, HS and Siegal, 38 (eds). Some methods ofestimation,lsr statistically underdeveloped areas. Methods and materials ofdemography. Academic Press, Orlando, Fla, 1974.5. NSW Health Department. inpatient Statistics i988/89.8. Carter FE, Barclay SM, Galloway WH, Cole GF. Changes in bacterialmeningitis. Arch Div Child 1990;65:495-498.7. Gilbert CL. Menisigococcal infections: 1990. Med JAust1990;153:507-508.8. Gilbert CL, Clements A, Broughton SJ. Hamophilus influenzaetype b infections in Victoria, Australia, 1985 to 1987. Fed infect Die J1990;9:252-257.9. Benenson AS led). Control of Communicable Diseases in Man. 14thedition. American Public Health Association. Washington DC. 1935.10. Mandell GL, Douglas RG, Bennett JE. Principles and Practice ofinfectious Diseases. 3rd Edition. Churchill Livingstone. New York. 1990.

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