ARCHIVED - Final report and recommendations from the National Notifiable Diseases Working Group

1 October 2006

Volume 32

Number 19

J-A Doherty, MSc (1)

1. Notifiable Diseases Section, Surveillance and Risk Assessment Division,
   Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, Ottawa, Ontario.

Summary

The National Notifiable Diseases Working Group performed a ranking of 48 communicable diseases to assist with determining priorities for national surveillance. The WG offers six specific recommendations relating to the addition or deletion of communicable diseases from the list of nationally notifiable diseases.

Key Recommendations

• Clostridium difficile-associated diarrhea, paralytic shellfish poisoning, and invasive listeriosis are recommended for addition to the Nationally Notifiable Disease List.

• New proposals for diseases not recommended for national notification include hepatitis E, HTLV-1, and HTLV-2.

• Dengue virus infection should be deleted from the Nationally Notifiable Disease List. (Dengue hemorrhagic fever should continue to be reported.)

• Classic Creutzfeld-Jacob disease ranked well below the threshold for inclusion; however, it should be retained on the list because surveillance of classic CJD is key to effective surveillance of new variant disease and because consulted provinces and territories strongly favoured its retention.

• Several diseases that ranked near the borderline for reporting should be retained on the list as follows:

• a. brucellosis, because although it does not rank highly on the basis of its endemic pattern it is a category B biological warfare agent;

• laboratory-confirmed influenza because it forms part of a functional and working surveillance approach;

• group B streptococcal infection because alternative hospital-based surveillance systems do not yet capture a significant proportion of cases.

• Transfusion-transmitted infections were unrankable by the current system.

• The approach to reporting dengue hemorrhagic fever, plague, West Nile virus infections, and other viral hemorrhagic fevers should be made congruent with the approach for other notifiable diseases (see Discussion).

• The feasibility and utility of national reporting for communicable diseases that have very high incidence and low severity (e.g. chickenpox, norovirus) should be carefully considered, especially when it leads to little or no case-by-case data reported by health authorities. The WG recommends that these diseases be placed under surveillance but that case-by-case reporting not be required at the national level. Alternative approaches to tracking trends could include enumerating outbreaks in the case of norovirus or the use of sentinel surveillance, laboratory surveillance, or physician billing events in the case of varicella.

Table 1: List of nationally notifiable diseases (as determined by the priority-setting exercise)

Acute Flaccid Paralysis
AIDS
Anthrax - reportable to WHO
Botulism - reportable to WHO
Brucellosis
Campylobacteriosis
Chickenpox
Chlamydia, Genital
Cholera - reportable to WHO
Clostridium difficile-associated diarrhea
Creutzfeld-Jacob Disease, Classic
Creutzfeld-Jacob Disease, New Variant
Cryptosporidiosis
Cyclosporiasis
Diphtheria
Giardiasis
Gonorrhea
Group B Streptococcal Disease of the Newborn
Hantavirus Pulmonary Syndrome
Hepatitis A
Hepatitis B
Hepatitis C
Human Immunodeficiency Virus
Influenza, Laboratory Confirmed
Influenza (New Subtype) - reportable to WHO
Invasive Group A Streptococcal Disease
Invasive Haemophilus influenzae type B
Invasive Meningococcal Disease - reportable to WHO
Invasive Pneumococcal Disease
Legionellosis
Leprosy
Listeriosis
Lyme Disease
Malaria
Measles
Mumps
Norovirus Infection
Paralytic Shellfish Poisoning
Pertussis
Plague (Pneumonic) - reportable to WHO
Plague - all types reportable to NDRS

Poliomyelitis (Wild Type) - reportable to WHO
Rabies
Rubella
Rubella, Congenital
Salmonellosis
SARS - reportable toWHO
Shigellosis
Smallpox - reportable toWHO
Syphilis, All Categories
Tetanus
Tuberculosis
Tularemia - reportable to WHO
Typhoid
Verotoxigenic E.coli
Viral Hemorrhagic Fevers - reportable to WHO

West Nile Virus Infection
Yellow Fever - reportable toWHO

Introduction

Communicable diseases (CDs) are made notifiable in the provinces and territories of Canada by provincial and territorial statute. The purpose of making a specific communicable disease reportable is to facilitate both tracking and required control efforts by public health personnel.

Canada's Nationally Notifiable Disease (NND) List has been published and reviewed periodically^1,2. The NND list helps to promote uniformity and synergy among the provincial and territorial efforts, and conformity with international reporting requirements. The changing epidemiology of infectious diseases requires that review and modification of the NND list be conducted periodically.

Methods

The National Notifiable Diseases Working Group (WG) is an assembly of epidemiologists and laboratory experts from provinces and territories and from the Public Health Agency of Canada
(Appendix 1). This group is derived from the previously constituted Communicable Disease Surveillance Standards Committee and is representative of members of the Canadian Public Health Laboratory Network and of the newly established Communicable Disease Control Network. The two latter groups represent expert working groups of the Canadian Public Health Network.

The group adapted a previously developed ranking system for notifiable diseases^1-4. The ranking system is detailed in Appendix 2. Substantive changes from the previous approach included the following:

• The development of specific guidelines for ranking within each criterion. For example, ranking of incidence was based on known rates of reporting for the CD and according to quartile of distribution.

• A numeric score was not assigned for internationally notifiable diseases. Rather, these were automatically included in the final list so that Canada would be in compliance with international requirements.

• Some criteria were broadened. For example, a previous criterion, “Agriculture Canada Interest”, was broadened to “Interest for National/International Regulatory and Prevention Programs”. Similarly, “Vaccine Preventability” was broadened to “Preventability” so as not to bias toward one form of intervention, although vaccine preventable diseases rated highly against this criterion.

Results

After putting aside the 12 CDs that are internationally notifiable, 48 other diseases were reviewed. Summary ranking results are displayed in Table 2.

The 12 diseases that are internationally notifiable were automatically included on the final list without being ranked: anthrax, botulism, cholera, influenza (new sub-type), invasive meningococcal disease, pneumonic plague, poliomyelitis, SARS (severe, acute respiratory syndrome), smallpox, tularemia, viral hemorrhagic fevers and yellow fever. (The general notifiability of plague is discussed below.)

For CDs ranked according to the criteria, the scores ranged from 12 to 34 with a median of 24.5 and a mode of 27 (see Table 2). After a careful review of the characteristics of the ranked diseases, a value of 18 was determined by a consensus of the WG to be the cut-off value for inclusion in the list of reportable diseases. This was not meant to be an absolute rule but, rather, to serve as a guideline to permit recognition of those CDs that lie on the borderline for inclusion as an NND and require further discussion. There were five specific issues that need further discussion and consensus at the level of the Canadian Public Health Network (see Discussion).

The WG reviewed each disease made nationally notifiable in 2000, as well as diseases suggested for addition to the list, according to a specific set of ranking criteria (Appendix 2). The review process consisted of an initial ranking by subgroups containing at least one epidemiologist and one laboratory expert, followed by a plenary review. The subgroups performed this scoring and ranking exercise blind to the previous rankings (done in 2000). During plenary review, the group searched for and corrected any major discrepancies in the application of guidelines to criteria.

Table 2. Results of the priority-setting exercise: disease by score

Table 2. Results of the priority-setting exercise: disease by score (continued)

There were three new diseases that ranked among those that will be recommended for reporting:

• Clostridium difficile-associated diarrhea
• Paralytic shellfish poisoning
• Invasive listeriosis
• Previously listed or proposed new diseases that fell below the threshold for inclusion were as follows:
  • Classic Creutzfeld-Jakob Disease
  • Dengue
  • Hepatitis E infection
  • HTLV-1
  • HTLV-2

Discussion

Several issues arose during this process that deserve particular mention. The “B-list for biological warfare agents” and automatic inclusion as NNDs

According to its long-term endemic characteristics, brucellosis did not score high enough for inclusion on the list. Specifically, theWG determined that incidence in Canada, communicability, potential for outbreaks, risk perception, and appearance of change scored very low as compared with other NNDs. Its inclusion on the “B list” for possible biological warfare agents is an important consideration, and theWG recommends that brucellosis be included as an NND.

Plague

All forms of Yersinia pestis infection, whether pulmonary, bubonic or other, ranked sufficiently high to warrant inclusion on the list. The WG recommends that the internationally notifiable condition of pneumonic plague be considered a subset of the overall category rather than a separate entity. From a practical standpoint, it is anticipated that communication between PHAC and a province or territory reporting human plague would occur routinely and that there would be sufficient clarity as to which are pneumonic cases for international notification.

Practical issues around reporting diseases at high incidence: chickenpox,
laboratory-confirmed influenza, and norovirus infections

These diseases each scored high enough on the ranking to be considered for reporting. However, their very high incidence requires a practical consideration of how they will be reported in order to avoid inundating public health personnel under a mountain of reports leading to little or no case-by-case action.

Chickenpox will soon become a crucial indicator of the success of broadly based varicella immunization programs. However, in 2006 case-by-case reporting may not yet be practical in all jurisdictions. The present status is that some jurisdictions do not report, others report aggregate figures at varying intervals, and a few report case by case.

Rather than requiring case-by-case reporting, it is more practical to seek information from sentinel health units, sentinel physicians, or related hospitalizations and physician billings.

Laboratory-confirmed influenza cases remain a small minority of influenza infections and do serve to inform the FluWatch program or other initiatives of the distribution of strains in circulation in the population. As this is an operative program that seems to have passed the test of logistic feasibility, theWG does not have grave concerns unless the volume of laboratory testing increases dramatically. In the event of an established pandemic, there should be no expectation of continued case-by-case reporting from laboratories, as this would not be logistically feasible.

In spite of the fact that norovirus infections scored 20, it would be more feasible to track norovirus outbreaks using outbreakmonitoring tools than to attempt case-by-case reporting.

In general terms, when a CD of interest has very high incidence in Canada and low severity, the feasibility and utility of national reporting should be carefully considered, especially when reporting leads to little or no case-by-case action from health authorities. The data regarding these CDs could be collected by other means.

Communicable diseases on the borderline: neonatal group B streptococcal infection and cyclosporiasis

Neonatal group B streptococcal infection scored 18 - the cut-off for inclusion. After review of coverage by the Canadian Pediatric Surveillance System, theWG concluded that reporting of neonatal group B streptococcal infection is still necessary.

Cyclosporiasis also had a borderline score of 18. The WG expressed concern that the infection is becoming an increasing problem because of our patterns of produce importation. Reporting to public health remains the main method of surveillance. Investigation of outbreaks is an important means of intervening to reduce morbidity and inform regulatory authorities. Consequently, the WG recommends that cyclosporiasis remain listed as an NND.

Review of broad or non-specific case definitions

The established criteria work relatively well for distinctly defined infections caused by identifiable and named micro-organisms; however, theWG was asked to consider several entities for inclusion for which this was not the case.

The broad category of “Diseases Caused by Pre-formed Toxins in Water and Food” was reviewed. Taken as a whole, this category did not rank highly and was a diffuse target for exercising the ranking criteria. This category could include a broad array of diseases caused by pre-formed enterotoxins from various organisms with largely temporary impact and no potential for secondary spread. Such outbreaks already come to the attention of local health authorities for investigation (usually as unspecified enteric outbreaks). By contrast, paralytic shellfish poisoning, like botulism, is a potentially lethal intoxication and its reporting leads to both public health intervention to limit further consumption of associated bivalves and review of fisheries regulations and postings. Accordingly, the WG modified this suggested addition, reviewing it as paralytic shellfish poisoning, and has recommended its inclusion in the list of notifiable diseases.

Viral hemorrhagic fevers (VHF) are also a broad category but are less problematic because the case definition contains a listing of specific agents, and the associated syndrome is generally recognizable and a cause of universal concern. The incorporation of separately listed NNDs as subcodes of VHF rather than as distinct and redundant items should be considered (e.g. Rift Valley Fever). In addition, while the WG recommended that dengue infections in general should be dropped from the list of reportable diseases, it suggested that dengue hemorrhagic fever should remain reportable as a specific subcode within VHF.

The WG did not find it possible to apply the criteria to the suggested “Transfusion-Transmitted Infections”. The following were noted:

• the operation of the NND system requires reasonably specific and operable case definitions;
• such a definition was not available at the time of review;
• the vast majority of infections known to play a role in transfusion-associated disease are specifically reportable.

The WG established that infections caused by the West Nile Virus should be included as NNDs. This remains true even of asymptomatic infections at present because of both their role in heralding the arrival of the virus in new human populations and their importance in assessing risk to the blood supply. On the other hand, the representation of WNV as three separate reportable entities (West Nile Neurological Syndrome, Symptomatic West Nile Infection, and Asymptomatic West Nile Infection) was not congruent with the internal logic of the notifiable disease list. Accordingly, the WG recommended that all confirmed West Nile infections be reportable and that the three categories described be submitted as subcodes for the one infectious disease, so that, for example, the relative burden of neurological syndromes can still be tracked.

Comparison with past ranking

The relative ranking of infectious diseases previously assessed during 2000 was generally coherent with the current effort. Because the ranking system has been modified with the intention of increasing its objectivity, which has resulted in specific changes within the criteria and how the CDs are ranked, there should be no expectation of a close concordance of absolute score for a particular CD between 2000 and 2005. Furthermore, the WG has emphasized that the absolute score of an NND is not as important as its position within the ranking of all NNDs together with the cut-off value.

Limitations

• Information available through reporting systems will be less than complete for some diseases and could lead to misallocation on the “incidence” scale.

• Figures for cost per case at the health care system or societal level were not available to inform the socio-economic burden ranking.

• In piloting this system, the WG noted close concordance of overall ranking between individual observers, although there was some variation between values assigned for each criterion. A broad assessment of inter-observer variability was not performed.

• Not all CDs can be applied perfectly to the ranking system. The nuances of each CD were taken into consideration in the determination of the final score.

• The hierarchical ranking obtained for each NND is not to be construed as a hierarchical ranking of the importance of each NND.

• The score of a given infectious disease would be expected to change over time as a result of a number of epidemiologic and biologic variables of the disease.

Next Steps

The Laboratory Standardization Subcommittee of the Canadian Public Health Laboratory Network has been working on updating a document linking case definitions to current laboratory diagnostic methods, associated standards, and proficiency requirements. The CDC Network with its expert groups will review the epidemiologic case definitions. The new list of NND will be effective upon publication of the case definitions. Provincial epidemiologists and laboratory directors will make sure that it is disseminated to public health groupings within each province and territory. PHAC personnel and provincial counterparts will work to ensure that reporting standards and existing systems are configured to support the new list.

References

1. Establishing goals, techniques and priorities for national communicable disease surveillance. CDWR 1991;17:79-84.

2. Doherty J. Establishing priorities for national communicable disease surveillance. Can J Infect Dis 2000;11:21-4.

3. Carter A. National Advisory Committee on Epidemiology SubCommittee. Establishing goals, techniques and priorities for national communicable disease surveillance. Can J Infect Dis 1991;2:37-40.

4. Carter AO. Setting priorities: The Canadian experience in communicable disease surveillance. MMWR 1992;41(Suppl):79-84.

Appendix 1: Membership of The Working Group

1. Dr. David Patrick
   Director, Epidemiology Services
   BC Centre for Disease Control
   655 West 12th Ave., Rm 2104
   Vancouver, BC V5Z 4R4

2. Ms. Jo-Anne Doherty
   Manager, Notifiable Diseases Section
   Surveillance & Risk Assessment Division
   Centre for Infectious Diseases Prevention and Control
   Public Health Agency of Canada
   AL: 0602B, Tunney's Pasture
   Ottawa, ON K1A 0L2

3. Dr. Robert Pless
   Manager, Surveillance Standards Development Programs
   Public Health Training & Applications Division
   Centre for Surveillance Coordination
   Public Health Agency of Canada
   120 Colonnade Road
   Ottawa, ON K1A 0K9

4. Ms. Carole Scott
   Surveillance Officer, Notifiable Diseases Section
   Surveillance and Risk Assessment Division
   Centre for Infectious Disease Prevention and Control
   Public Health Agency of Canada
   AL: 0602B, Tunney's Pasture
   Ottawa, ON K1A 0L2

5. Dr. Faith Stratton
   Director, Disease Control & Epidemiology
   Department of Health
   Government of Newfoundland and Labrador
   P.O. Box 8700
   St. John's, NF A1B 4J6

6. Dr. Paul Van Caeseele
   Laboratory Director
   Cadham Provincial Laboratory
   Box 8450, Winnipeg, MB R3C 3Y1

7. Dr. André Corriveau
   Chief Medical Health Officer, Department of Health &
   Social Services
   Government of Northwest Territories
   P.O. Box 1320
   Yellowknife, NT X1A 2L9

8. Dr. Sam Ratnam
   Director, Newfoundland Public Health Laboratory
   The Leonard A. Miller Centre for Health Services
   100 Forest Road, P.O. Box 8800
   St. John's, NF A1B 3T2

9. Dr. Amin Kabani
   Senior Medical Officer
   National Microbiology Laboratory
   Public Health Agency of Canada
   1015 Arlington Avenue
   Winnipeg, MB R3C 3P6

10. Dr. Monique Douville-Fradet
    Médecin spécialiste
    Risques biologiques, environnementaux et
    occupationnels
    Institut national de santé publique du Québec
    2400, rue d'Estimauville, Beauport, QC G1E 7G9

11. Ms. Shirley Paton
    Chief, Nosocomial and Occupational Infections
    Blood Safety Surveillance and Health Care Acquired
    Infections Division
    Centre for Infectious Disease Prevention and Control
    Public Health Agency of Canada
    AL: 0601E2, Tunney's Pasture
    Ottawa, ON K1A 0L2

12. Ms. Leanne DeWinter
    Standards Development Officer
    Canadian Public Health Laboratory Network
    National Microbiology Laboratory
    Public Health Agency of Canada
    1015 Arlington Street
    Winnipeg, MB R3E 3R2

13. Dr. Theodore Kuschak
    Manager, Canadian Public Health Laboratory Network
    National Microbiology Laboratory
    Public Health Agency of Canada
    1015 Arlington St, Winnipeg, MB R3E 3P6

14. Dr. Graham Tipples
    Director, Surveillance and Reference Services
    National Microbiology Laboratory
    Public Health Agency of Canada
    1015 Arlington Avenue, Winnipeg, MB R3E 3R2

Appendix 2: Criteria And Guidelines For Ranking

1. National/international regulatory and prevention programs

This criterion addresses whether diseases are of interest to organizations, such as regulatory authorities, for disease surveillance data that could guide prevention or regulatory programs. Examples of these organizations are Agriculture Canada, Canadian Blood Services, and the Canadian Food Inspection Agency. A sense of “urgency” of direct public health action should also be considered when scoring this criterion. In addition, the criterion incorporates part of theWHO International Health Regulations and the list of diseases of interest to theWHO Department of Communicable Disease Surveillance and Response (CSR). The diseases of interest for this purpose are West Nile virus infection, Rift Valley fever, dengue, and invasive meningococcal disease.

Criterion #1: Diseases of Interest to Organizations to Inform Prevention and Regulatory Programs

2. Incidence in Canada

The 5-year average incidence divided into quartiles and “critical incidence”, in which just one case would be significant (e.g. smallpox). Anchor points are based on the maximum 5-year average rate of current notifiable diseases (data from reporting provinces/territories only).

Criterion # 2: 5-Year Average Incidence

3. Severity

This criterion combines the formerly separate Morbidity, Mortality, and Case-Fatality Rate criteria. Available data are collected and summarized to support the rating scheme. Informed expert opinion is used to create and apply the scoring structure for this criterion.

Criterion #3: Severity

4. Communicability/potential spread to the general population

Based on efficiency of transmission from person to person, animal to human, or food/water/environment to human.

Criterion #4: Communicability/Potential Spread to the General Population

5. Potential for outbreaks

Based on ability to cause outbreaks. Consider size of outbreak and number of outbreaks.

Criterion #5: Potential for Outbreaks

6. Socioeconomic burden

Diseases/conditions subjectively ranked according to the costs to society associated with each case of disease, including immunization programs, long-term disability, non-hospital care, years of potential life lost.

Criterion #6: Socioeconomic Burden

7. Preventability

Subjectively ranked, based on the efficacy (including risk/benefit) of available preventive measures, including, but not restricted to, vaccines.

Criterion #7: Preventability

8. Risk perception

Subjectively ranked, based on various aspects of perception of risk to personal health associated with having the disease, including media attention, immediacy of the effect of disease, level of fear, unknown or unclear disease mechanism, dreaded versus familiar, affecting mainly children, “identifiable victims”, not controllable by the public. This criterion is not measuring public perception of the chance of acquiring the disease; this is ranked in the preventability and communicability criteria.

Criterion #8: Risk Perception

 

9. Necessity for public health response

Subjectively ranked, based on the need and efficacy of a response by public health authorities to prevent other cases of the disease, e.g. case and contact management.

Criterion #9: Necessity of Public Health Response

 

10. Appearing to increase in incidence or change patterns over the past 5 years

Subjectively ranked, based on how the disease appears to be emerging or is re-emerging and whether the disease is anticipated to change or has ongoing change. Consider the following: whether it is a newly appeared disease or an unexpected/unusual event and the factors that could modify its clinical and/or epidemiologic characteristics, such as changes in demographic features, rapid spreading capacity, resistance to antibiotics, appearance/reappearance of the disease, vulnerable groups/accumulations of susceptible people, environment/climate factors, changes in the ecology of vectors.

Criterion #10: Increasing or Changing Patterns