Sentinel Health Unit Surveillance System

T HE CANADIAN PUBLIC HEALTII SYSTEM lS CONSTANTLY challenged to develop disease prevention and control strategies for Canada. These strategies need to be developed using Canadian population-based data collected on the incidence of and the risk factors associated with selected diseases. Surveillance data can be used to determine the need for public health action. as well as to assess the effectiveness of public health strategies. The information gathered through epi demiological surveillance should be used for planning, implementing and evaluating public health programs (l). National surveillance activities in Canada are pri marily focused on the 45 notifiable diseases for which the Bureau of Communicable Disease Epidemiology, Laboratory Centre for Disease Control (LCDC). receives information monthly from provinces and territories. Information given for these diseases includes numbers of cases and a breakdown by sex and age group (2). Detailed information on individual cases is received from six provinces and the territories. Administrative data sets collected by Statistics Canada. hospital discharge databases (HMRI and Med ECIIO). provincial cancer registries. etc, have provided information on other diseases and health conditions. Information from all these sources has limitations in that its formal. quality and/or timeliness may not be sufficient for national surveillance needs. Sentinel systems used for surveillance are an effective public health tool. which has been used in other countries and has proven useful in the monitoring of many diseases (3). In Canada. sentinel physicians have been used in some provinces to monitor influenza ac-

challenged to develop disease prevention and control strategies for Canada.These strategies need to be developed using Canadian population-based data collected on the incidence of and the risk factors associated with selected diseases.Surveillance data can be used to determine the need for public health action.as well as to assess the effectiveness of public health strategies.The information gathered through epidemiological surveillance should be used for planning, implementing and evaluating public health programs (l).
National surveillance activities in Canada are primarily focused on the 45 notifiable diseases for which the Bureau of Communicable Disease Epidemiology, Laboratory Centre for Disease Control (LCDC).receives information monthly from provinces and territories.Information given for these diseases includes numbers of cases and a breakdown by sex and age group (2).Detailed information on individual cases is received from six provinces and the territories.Administrative data sets collected by Statistics Canada.hospital discharge databases (HMRI and Med ECIIO).provincial cancer registries.etc, have provided information on other diseases and health conditions.Information from all these sources has li mitations in that its formal.quality and/or timeliness may not be sufficient for national surveillance needs.
Sentinel systems used for surveillance are an effective public health tool.which has been used in other countries and has proven useful in the monitoring of many diseases (3).In Canada.sentinel physicians have been used in some provinces to monitor influenza ac-tivity.Sentinel networks.linking participating organizations to centralized data collection.have been particularly helpful in monitoring specific targeted d iseases or disease groups.One such network in use in Canada is the IMPACT System, a hospital-based active surveillance system for monitoring adverse events following immunization.
LCDC. recognizing the need for a public health network for targeted surveillance, recenlly established the Sentinel Health Unit Surveillance System.This system was designed as a flexible surveillance method to address the need for specific information on targeted diseases.The goal of this community-based system is to provide reliable demographic, risk factor and other epidemiological and laboratory data necessary for the development of strong public health policy.
The Sentinel Health Unit Surveillance System is designed to: • collect information that will help define key public health issues and will assist in the development of appropriate prevention/control strategies at both provincial and national levels: • assist in the monitoring and evaluation of current prevention/control strategies: and • encourage the development of a public health network that includes epidemiological and laboratory expertise.

SENTINEL SITES
Provincial epidemiologists were asked to identify health units potentially interested in participating in this system.The goal was to identify health units where the residents were likely to seek all of their health care within the health unit jurisdiction.Nine health units in eight provinces are participating in the system (Figure 1).These units represent approximately 10% of the Canadian population and are a mixture of urban and rural communities .Although the h ealth units m ay not be fully representative of the Ca n ad ia n popul a tion.efforts h ave been ma de to ensure all major population groups a re re presented.Four of the h ea lth units are loca ted in me tropolitan centres h aving populations greater than 180.000.while the re ma ining units ar e in small er urban and rural co mmuniti es (Tab le 1).

ORGANIZATION
The Sentinel Health Un it Survei ll a nce System depends on active colla boration among the provinci a l ministries of h ealth.the pa rticipating h ealth units.and ll ealth Can ada , as we ll as with other key community participants .Provincial epide miologis ts (members of the Advisory Committee on Epidemiology).provincia l laboratory directors (membe rs of the Technical Advisory Committee), representa tiv:::s from each of the sentinel health units and staff from the bureaus of Co mmuni cable Disease Ep ide miology .Chronic Disease Ep id emiology and Microbio logy, respectively. of LCDC.participate in the planning a nd developme nt of the system's activities.
An advisory committee.with re presenta tion from th e above groups as well as community groups.is b eing developed.This committee will estab lis h the overall direction for the system.a nd will oversee th e identifi cation and development of proj ects.Each h ealth unit is also responsible for es tablishing a local advisory gro up.
A coord inator located in the Bureau of Co mmunicable Disease Epidemiology acts as the lia ison to the participa ting h ealth units .a dviso ry and expe rt commitlees.a nd staff of LCDC.Negotiations a re und erway to establish s ile coordinators in eac h of the pa rti cipa ting 208 * * *• P Sites Figure 1) Sentinel health unit s ites as qj'Augusl 1994 h ealth units.These coordinators will provide the local coordina tion and support to the network.
To facilitate communications among key players and th e sentinel sites, a regu lar newsletter is being pla nned .As well.each of U1e sites has been connected to a n elec tronic conferen ce on LCDC's Health Information Ne twork (4).This will a llow ready communication of id eas an d iss u es a mong the s ites.Th is infrastructure will c rea te a sentinel public h ealth network that can be responsive to Canadian n eeds.

PROJECT SELECTION AND DEVELOPMENT
Proposed proj ec ts will be revi ewed by the adviso ry committee.If the proj ect is considered a ppropriate and timely.a working group will b e identified with specific expertise in the area under considera tion.This group is responsible for th e identifica tion of the study qu estion .the development of the study design.and determination of the ep idemiological and la bora tory methods to be used in the study.The protocol will b e referred back to the advisory committee for fin al approval.
Th e Sentinel Health Unit Surveillance Syste m is curre nlly carrying out targe ted surveillance for viral he patitis (A Band C) .Qu es tionnaires are a dministe red to each eligible case and a blood specimen is fonva rded to the Bureau of Microbiology for further laboratory a n a lysis .Th e goals of this proj ect a re to de termin e the incidence of and risk factors for viral h epatitis, to determin e pers onal and economic costs of the disease a nd to evalu ate c urrent control m easu res.Informa tion from th is study will assist in th e development of na tional control guidelin es.
Other projects unde r d evelopment include a schoolbased survey of as thma in school-aged children.Approximately 3000 ch ildren (with their parents) in eac h hea lth unit will be s urveyed to determine whether they h ave ever been diagnosed with asthma .Those who report a history of as thma will be asked to participate in a more in -depth face to face interview.Data collected from this enhanced surveilla n ce will cover prevalen ce.incide n ce, severity, treatment a nd use of health services a nd will supp le m e nt data obta in ed from the National Population Health Survey.A ta rge ted surveilla n ce proj ect for seve re respira tory d isease in young children is being planned for 1995-96.

SUMMARY
Public h ealth sen tin el surveil la nce systems a re a n efficient way to monitor selected diseases/ health conditions of Canadians.They can provide data tha t will bu il d on and complem ent other surveillance activities.Data generated by the Sentinel Health Unit Surveillance System will contribute both a regional and a national picture of the h ealth of Canad ians and an understanding of the role of identified risk factors for acqu is ition of the disease under study.This information \viii assist in the development of sound n a tiona l po licies and effective co ntrol strategies .For furth er CAN J INFECT DIS VOL 5 No 5 SEPTEMBER/OCTOBER 1994 LCDC Report informa tion on thi s syste m .contact Ms Cathy Anderson.Sen tinel Health Un it Coord inato r. telephone (306) 966-7943.fax (306) 966-7920.In ternet Ande rson @herald .usask.ca.