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The Canadian Pandemic Influenza Plan for the Health Sector
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Annex N
Pandemic Influenza Surveillance Guidelines
Date of Latest Version: October 2006 Note: This is a new annex being released with the 2006 version of the Canadian Pandemic Influenza Plan. |
Table of Contents
- Preamble
- Introduction
- Interpandemic Period
- Appendix I: Generic Serosurvey Protocol of People Exposed toInfluenza
- Appendix II: National Flu Watch Influenza Surveillance System
- Appendix III: National SRI Investigation Report Form Data Element
Preamble
Since 2004, Canadian public health surveillance stakeholders, through national working groups, have been defining the roles, responsibilities as well as the minimum standards for national surveillance data to be collected during interpandemic and pandemic periods.
The ability to adapt to rapidly evolving situations must be included in all surveillance guidelines. As such, the following annex is part of an ongoing and evolving preparedness plan. It is recognised that while the current published version outlines high level surveillance guidelines, further detail is required in order to provide comprehensive national guidelines, in particular, a more detailed description of streamlined surveillance activities for phase 6.
Therefore, the annex should be considered with the following list of next steps:
- Review of the sustainability of routine surveillance activites and consideration of options for streamlined surveillance which may include either greater focus on more reliable indicators or modification/simplification of routine activities during a pandemic
- Prioritize surveillance activites by phase
- Explore options and feasibility for development of new surveillance activities as part of preparedness, e.g. real-time mortality surveillance.
Introduction
The overall goals of influenza pandemic preparedness and response are:
First, to minimize serious illness and overall deaths, and second to minimize societal disruption among Canadians as a result of an influenza pandemic.
The strategies used to achieve these goals will depend on a number of factors including the epidemiology of the pandemic. Determination of epidemiological parameters and indicators are critical for informing the public health response. As the pandemic progresses through each phase, the surveillance activities needed to guide public health actions will change from enhanced activities in the pandemic alert phases to streamlined activities at the height of the pandemic.
In this document, influenza surveillance guidelines, including data collection, collation, analysis and dissemination/communication issues for both disease and virologic surveillance are outlined for each phase of the pandemic. In addition, detailed protocols for virologic surveillance and other laboratory procedures can be found in the laboratory annex of the Canadian Pandemic Influenza Plan (Annex C).
This document has been prepared for pandemic planning purposes as well as to facilitate a standardised approach to national influenza surveillance during the interpandemic period. While the characteristics of a novel influenza virus are not known, the experiences learned from both SARS and outbreaks of human infection with influenza A (H5N1), have underscored the importance of preparatory planning and establishing a surveillance infrastructure capacity for the detection and monitoring of emerging respiratory infections. The following framework addresses planning for surveillance in general terms; however, it should be understood that while some of the recommended actions can be prepared for in advance, other situation-specific recommendations and alerts will need to be developed based on information that will only be available as the situation evolves.
Guidelines are necessary to ensure data are collected in a standardized manner across jurisdictions to enable national level analysis and cross-jurisdictional comparison. The guidelines represent the minimum recommended activities required for national monitoring of the evolving pandemic. Provincial and territorial jurisdictions may choose, based on their on own risk assessment and experience, to increase the sensitivity of surveillance activities (e.g. increased timeliness of data collection and reporting or use of more sensitive case definitions for monitoring) while respecting national health reporting standards. Further, as additional information becomes available during the course of the pandemic, monitoring and reporting activities may be refined as necessary.
The objectives of these guidelines are to assist federal, provincial and territorial (FPT) partners in the development or enhancement of surveillance activities that will facilitate:
- ongoing risk assessment for pandemic influenza based on national and international sources
- rapid detection and monitoring of the arrival of a novel/pandemic influenza virus anywhere in Canada,
- timely description of the epidemiologic and virologic characteristics of the pandemic
- detection and characterization of unusual/unexpected disease patterns or manifestations
- real-time monitoring of disease severity indicators i.e. through real-time surveillance of hospitalizations or deaths
- implementation and discontinuation of public health measures1
- ongoing evaluation of disease and virologic surveillance activities for each pandemic phase (e.g. timeliness, appropriate sensitivity and specificity, effectiveness in guiding public health measures)
- comparing novel influenza strains to match pandemic vaccine composition
- identification of areas of need for special studies and further research
Assumptions
- The Respiratory Illness Outbreak Response Protocol (RIORP)2 will be approved and implemented in order to facilitate data sharing and communication within Canada during the pandemic. This document outlines local, PT and federal reporting processes.
- Information on the current risk assessment, epidemiologic, virologic, and clinical descriptions (based on the global situation) will be available and shared in a timely manner via our international partners (e.g., WHO).
- The majority of, if not the entire population, will be susceptible to the pandemic strain.
- During the pandemic alert period (the early phases of the arrival of a novel virus with pandemic potential in Canada) detailed reporting of epidemiological data and contact tracing for initial cases by public health will be possible.
- As the efficiency of human-to-human transmission increases, resulting in widespread activity of the novel virus in Canada, surveillance resources are expected to be strained. This may impact participation and reporting rates for routine surveillance activities such as sentinel influenza-like illness (ILI) reporting. While in some areas participation may be maintained at sufficient levels for accurate monitoring population-based trends on a local or even provincial/territorial level, participation rates may fall off elsewhere thus limiting the representativeness of the data in certain areas or nationally. At the height of the pandemic, if population-based ILI rates become unreliable for monitoring disease spread/ population impact, particularly at the regional or national level, surveillance may be limited to tallying outbreaks in residential institutions and/or assessment of regional influenza activity levels (i.e. streamlined surveillance).
- The novel virus strain (pandemic strain) will supplant other circulating influenza strains.
- The pandemic will last 12 to 18 months and more than one wave may occur within a 12 month period and could have a similar or more severe impact than the initial wave.
- PHAC will follow guidelines as per the International Health Regulations.
Special Studies
Protocols for special studies which may be conducted during the pandemic should be developed and pre-tested in the interpandemic/pandemic alert periods, recognizing that refinements may be necessary at the time of a pandemic. It is recognised that these studies will most likely be conducted in parallel to other surveillance activities.
Special studies may include, but are not limited to, serological surveys3 of early cases/clusters of human infection with a novel influenza virus, vaccine effectiveness studies, role of bacterial pathogens in the development of secondary complications and serious outcomes, investigation of reported adverse events following immunization (AEFI), antiviral resistance monitoring, and modes of transmission studies (e.g. in community or hospital-based settings).
In addition, targeted studies may be useful in supplementing routine surveillance data to assess the impact of the pandemic on the health care system as well as in terms of social and economic impact. Even if conducted at the end of the pandemic wave, special studies may serve as a means of evaluating and refining various attempted interventions to lessen the impact of successive waves of the pandemic.
Surveillance Activities by Canadian Pandemic Phases
Surveillance for pandemic influenza is expected to be founded on timely, representative and comprehensive surveillance activities that are the cornerstones of ongoing routine annual influenza surveillance, including:
- Disease/epidemiologic surveillance
- Laboratory/virologic surveillance, including antiviral resistance monitoring
- Ongoing information sharing through established communication networks (e.g. CIOSC, FluWatch, provincial and territorial networks)
Several additional activities are recommended for pandemic influenza surveillance both for enhanced detection of early warning signals and for monitoring during a pandemic, including:
- Animal health surveillance (early detection of animal outbreaks and/or animal-to-human transmission in interpandemic and pandemic alert periods)
- Monitoring vaccine and antiviral uptake
- Monitoring of adverse events following immunization
The following tables describe the surveillance objectives, roles and responsibilities for public health stakeholders at each level of government (federal, provincial/territorial and local). The tables are organized by successive phases of a pandemic based on the Canadian Pandemic Phases which reflects both the global situation (phases 1.0, 2.0, 3.0, etc.) as well as the highest level of novel virus activity in Canada (sub-phases 3.1, 4.1, 5.1, etc.). See the Background Section of the Canadian Pandemic Influenza Plan for more details.
Note: In the description of the phases the term "animal" is used to cover both avian and mammalian species.
Interpandemic Period
| Canadian Pandemic Phase |
1.0 No new virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection may be present in animals located outside of Canada. If present in animals, the risk of human infection/disease is considered to be low. 1.1 No new virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection is present in animals in Canada but the risk of human infection/disease is considered to be low. 2.0 No new virus subtypes have been detected in humans. However, an animal influenza virus subtype that poses substantial risk to humans is circulating in animals located outside of Canada. 2.1 No new virus subtypes have been detected in humans. However, an animal influenza virus subtype that poses substantial risk to humans is circulating in animals in Canada. |
| Surveillance Objectives/Roles and Responsibilities |
Objectives:
Federal:
Federal:
P/T/local:
|
Table 1.1: National Surveillance Data during the Interpandemic Period5
| Canadian Pandemic Phase |
1.0 No new virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection may be present in animals located outside of Canada. If present in animals, the risk of human infection/disease is considered to be low. 1.1 No new virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection is present in animals in Canada but the risk of human infection/disease is considered to be low. 2.0 No new virus subtypes have been detected in humans. However, an animal influenza virus subtype that poses substantial risk to humans is circulating in animals located outside of Canada. 2.1 No new virus subtypes have been detected in humans. However, an animal influenza virus subtype that poses substantial risk to humans is circulating in animals in Canada. |
| National Surveillance Data |
Disease surveillance (a) influenza activity level by P/T region (based on FluWatch definitions) Laboratory surveillance (e) percent positive influenza tests (total number of
laboratory tests for influenza and number of positive results, by
virus type (A or B) Risk assessment (i) summary of national/international areas where animal virus activity has been confirmed |
*Appendix 2 provides a pictorial representation of the national FluWatch influenza surveillance system.
Pandemic Alert Period
Table 2, below, describes the surveillance objectives for the pandemic alert period. The objectives are general, given the unknown epidemiology of a novel influenza virus infection and uncertainties as to how it might behave in terms of efficiency of human-to-human transmission, impact on the population/population sub-groups and capacity to spread rapidly. Recommended surveillance tools and protocols, including surveillance case definitions, will need to be developed and revised based on information received as the situation evolves. The triggers that will signal the move to a new phase are generally based on relative ability to infect humans and spread efficiently among humans, as determined by observed activity and a comprehensive risk assessment. This risk assessment will include analyzing the interplay of these and other factors (e.g. infectiousness, rate of transmission, incubation period and period of communicability, severity of illness, impact of initial control measures, etc.). These factors should be viewed as general parameters which are useful for describing the critical points in the evolution and escalation of a pandemic and can only be assumed prior to strain identification and circulation of the novel virus. Furthermore, initial predictions are subject to change as the novel virus becomes adapted to human populations and flexibility will be important to respond to rapid adjustment of surveillance and related activities. As such, the following tables provide a basic framework for establishing and maintaining the recommended surveillance infrastructure and for clarifying basic roles and responsibilities to managing these activities at the various levels of government.
Supplementary Surveillance Recommendations - Ongoing Risk Assessment and Emerging Respiratory Illness Updates (Alerts/FYIs):
The ongoing maintenance and adjustment of routine surveillance activities and the timely sharing of surveillance and risk assessment information is an important supplement to the basic surveillance framework laid out in this annex. Based on ongoing risk assessment derived from the interpretation of local, regional, national and international influenza/emerging respiratory illness activity, recommendations may be made on an as-needed basis. These will guide increased vigilance and direct surveillance and investigation of severe and/or unexpected respiratory illnesses in relation to exposures of concern (high risk travel locations, exposure settings or types of contact). Furthermore, monitoring and investigation activities may be adjusted in terms of sensitivity and specificity as dictated by the evolving situation. Factors that may influence the opportunity for initial containment of cases/isolated clusters, such as the length of the incubation period and efficiency of transmission, will contribute to the decision of whether or not to continue case and cluster investigation with a view to controlling spread, if only temporarily, to buy additional time at the outset of a pandemic.7 The following framework should be considered with these factors in mind, underscoring the need for flexible, simple and proven activities/systems founded on good routine surveillance practices, clarified roles and responsibilities and efficient use of resources.
Table 2: Pandemic Alert Period
| Canadian Pandemic Phase |
| 3.0 Outside Canada human infection(s) with a new subtype are occurring, but no human-to-human spread, or at most rare instances of spread to a close contact has been observed. No cases identified in Canada. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
Additional roles/responsibilites for phase 3:
P/T/local: Additional roles/responsibilites for phase 3:
|
| Canadian Pandemic Phase |
| 3.1 Single human case(s) with a new subtype detected in Canada. Virus is not known to be spreading from human-to-human, or at most rare instances of spread to a close contact have been observed. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
P/T/local:
|
| Canadian Pandemic Phase |
| 4.0 Outside Canada small cluster(s) with limited human-to-human transmission are occurring but spread is highly localized, suggesting that the virus is not well adapted to humans. No cases identified with these cluster(s) have been detected in Canada. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
Additional roles/responsibilities for phase 4:
P/T/local:
Additional roles/responsibilities for phase 4:
|
| Canadian Pandemic Phase |
4.1 Single human case (s) with virus that has demonstrated limited human-to-human transmission detected in Canada. No cluster(s) identified in Canada. 4.2 Small localized clusters with limited human-to-human transmission are occurring in Canada but spread is highly localized, suggesting that the virus is not well adapted to humans. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
Additional roles/responsibilities for phase 4.1, 4.2:
P/T/local:
Additional roles/responsibilities for phase 4.1, 4.2:
|
| Canadian Pandemic Phase |
| 5.0 Outside Canada larger cluster(s) are occurring but human-to-human spread still localized, suggesting that virus is becoming increasingly better adapted to humans but may not yet be fully transmissible (substantial pandemic risk). No cases identified with these clusters have been detected in Canada. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
P/T/local:
|
| Canadian Pandemic Phase |
| 5.1 Single human case(s) with virus that is better adapted to humans detected in Canada. No cluster(s) identified in Canada. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
P/T/local:
|
| Canadian Pandemic Phase |
| 5.2 Larger localized cluster(s) with limited human-to-human transmission are occurring in Canada but human-to-human spread still localized, suggesting that virus is becoming increasingly better adapted to humans but may not yet be fully transmissible (substantial pandemic risk). |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
P/T/local:
|
Table 2.1: National Surveillance Data for the Pandemic Alert Period
| Canadian Pandemic Phase |
| 3.0 Outside Canada human infection(s) with a new subtype are occurring, but no human-to-human spread, or at most rare instances of spread to a close contact has been observed. No cases identified in Canada. |
| National Surveillance Data |
Disease surveillance (a) influenza activity level by P/T region (based on FluWatch definitions) Laboratory surveillance (e) percent positive influenza tests (total number of
laboratory tests for influenza and number of positive results, by
virus type (A or B)) Risk assessment (i) summary of national/international areas where animal virus
activity has been confirmed |
| Canadian Pandemic Phase |
| 3.1 Single human case(s) with a new subtype detected in Canada. Virus is not known to be spreading from human-to-human, or at most rare instances of spread to a close contact have been observed. |
| National Surveillance Data |
Disease surveillance (a) influenza activity level by P/T region (based on FluWatch definitions) Laboratory surveillance (e) percent positive influenza tests (total number of
laboratory tests for influenza and number of positive results, by
virus type (A or B)) Risk assessment (i) summary of national/international areas where animal virus
activity has been confirmed In addition to indicators for 3.0: (k) detailed epidemiological description and estimation of
incubation and communicability periods (e.g. number of secondary
cases) |
| Canadian Pandemic Phase |
4.0 Outside Canada small cluster(s) with limited human-to-human transmission are occurring but spread is highly localized, suggesting that the virus is not well adapted to humans. No cases identified with these cluster(s) have been detected in Canada. 5.0 Outside Canada larger cluster(s) are occurring but human-to-human spread still localized, suggesting that virus is becoming increasingly better adapted to humans but may not yet be fully transmissible (substantial pandemic risk). No cases identified with these clusters have been detected in Canada. |
| National Surveillance Data |
Same data as 3.0: (a) influenza activity level by P/T region (based on FluWatch definitions) Laboratory surveillance (e) percent positive influenza tests (total number of
laboratory tests for influenza and number of positive results, by
virus type (A or B)) Risk assessment (i) summary of national/international areas where animal virus
activity has been confirmed |
| Canadian Pandemic Phase |
4.1 Single human case(s) with virus that has demonstrated limited human-to-human transmission detected in Canada. No cluster(s) identified in Canada. 4.2 Small localized clusters with limited human-to-human transmission are occurring in Canada but spread is highly localized, suggesting that the virus is not well adapted to humans. 5.1 Single human case(s) with virus that is better adapted to humans detected in Canada. No cluster(s) identified in Canada. 5.2 Larger localized cluster(s) with limited human-to-human transmission are occurring in Canada but human-to-human spread still localized, suggesting that virus is becoming increasingly better adapted to humans but may not yet be fully transmissible (substantial pandemic risk). |
| National Surveillance Data |
Same data as 3.1: (a) influenza activity level by P/T region (based on FluWatch definitions) Laboratory surveillance (e) percent positive influenza tests (total number of
laboratory tests for influenza and number of positive results, by
virus type (A or B)) Risk assessment (i) summary of national/international areas where animal virus
activity has been confirmed In addition to data for 3.1: (o) # and epidemiological description of settings involved |
Pandemic Period
| Canadian Pandemic Phase |
| 6.0 Outside Canada increased and sustained transmission in general population has been observed. No cases have been detected in Canada. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
P/T/local:
|
| Canadian Pandemic Phase |
| 6.1 Single human case(s) with the pandemic virus detected in Canada. No cluster(s) identified in Canada. Note: It is likely that this phase will have a very short duration and may not occur at all in Canada (i.e., novel virus activity may not be detected prior to the occurrence of a cluster of cases). |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
P/T/local:
|
| Canadian Pandemic Phase |
| 6.2 Localized or widespread pandemic activity observed in Canadian population. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
P/T/local:
|
Table 3.1: National Surveillance Data for the Pandemic Period
| Canadian Pandemic Phase |
| 6.0 Outside Canada increased and sustained transmission in general population has been observed. No cases have been detected in Canada. |
| National Surveillance Data |
Disease surveillance (a) influenza activity level by P/T region (based on FluWatch definitions) Laboratory surveillance (e) percent positive influenza tests (total number of
laboratory tests for influenza and number of positive results, by
virus type (A or B)) Risk assessment (i) summary of international activity in humans |
| Canadian Pandemic Phase |
6.1 Single human case(s) with the pandemic virus detected in Canada. No cluster(s) identified in Canada. Note: It is likely that this phase will have a very short duration and may not occur at all in Canada (i.e., novel virus activity may not be detected prior to the occurrence of a cluster of cases). |
| National Surveillance Data |
Same data as 5.1, 5.2: Disease surveillance (a) influenza activity level by P/T region (based on FluWatch definitions) Laboratory surveillance (e) percent positive influenza tests (total number of
laboratory tests for influenza and number of positive results, by
virus type (A or B)) Risk assessment (i) summary of international activity in humans In addition to data for 5.1, 5.2: (o) # surveillance regions with widespread activity, based on FluWatch definitions NOTE: Presently, there is no mechanism for collecting mortality data on a real-time basis. This is a recognized gap in information for monitoring of severity of the pandemic. While required during inter-pandemic phases to monitor severity of annual influenza epidemics, establish baseline expected seasonal mortality trends and detect potential signals, real-time mortality surveillance is recommended at the height of a pandemic to describe the severity of the pandemic, identify high risk age groups and provide crude indications of intervention effectiveness. As well, during this heightened phase of the pandemic, resources are expected to be scarce and due to low participation/reporting rates, existing surveillance activities may no longer provide accurate or complete data. While routine surveillance activities are not expected to stop entirely, participation rates may be very low and therefore data quality and representativeness may be poor. As such, simple and flexible systems for surveillance are key. In addition to routine activities that are established and maintained, new and recommended activities, such as real-time mortality surveillance, should be simple and flexible. |
Post-Pandemic Period
While the post-pandemic period suggests that the pandemic waves have ended and that the virus is no longer causing significant outbreaks in the population, it is acknowledged that the virus will continue to circulate. The following outlines activities to evaluate the surveillance activities during the pandemic, however, surveillance and laboratory activities during this time should continue to monitor changes in the pandemic virus.
Table 4: Post-Pandemic Period
| Canadian Pandemic Phase |
| Post-Pandemic Reports of case counts and other broad indicators of pandemic activity in Canada suggest that the pandemic virus is no longer causing significant illness in the population. |
| Surveillance Objectives/Roles and Responsibilities |
Objective:
Federal:
P/T/local:
|
Appendix 1: Generic Serosurvey
Protocol of People Exposed to Influenza
Drafted by: The Vaccine Preventable and Respiratory Infections Surveillance (VPRIS) working group, April 2006.
Background
To understand the risk of new influenza strains to humans, it is important to know their capability to infect people and cause disease. During the recent years, several avian influenza strains caused outbreaks in animals with limited secondary transmission to humans. These human cases may potentially transmit their influenza to their various types of contacts: household, healthcare workers or social contacts. In the multiple possible scenarios regarding pandemic influenza, one expects strains that will become pandemic to initially be acquired from animals, cause limited transmission and progressively hone their capacity to infect humans through adaptative mutations or reassortment.
To identify potential pandemic strains, it is important to be able to define the transmissibility of these strains to humans as well as their virulence which is their capacity to cause serious disease. When an influenza strain infects a person, it will trigger an antibody immune response specific to this strain. The presence of these antibodies is an accurate marker of infection even in absence of symptoms. Serosurveys of persons who have been in contact with infected animals or humans are therefore helpful to estimate the transmissibility of new strains and their virulence when coupled with clinical symptoms.
This generic protocol describes a methodology to conduct serosurveys in people who have been in contact with infected animals or humans. This methodology has to be adapted to the specific context of the outbreak. While the influenza strains to investigate may be of swine origin or from another type of animal, the most likely hosts of strains that will raise concerns are birds. For simplicity, the protocol will refer to avian strain when speaking of the implicated animal strain.
This protocol is a synthesis of several serosurvey protocols used elsewhere in the world after or during outbreaks of avian influenza. It describes a method that can be used with the three most frequent types of contacts investigated: workers and people in contact with infected animals, household contacts of human cases and healthcare workers in contact with patients. The study design and variables to collect will vary for each situation but laboratory assessment is common to all studies. The proposed questionnaire presents a series of questions and variables that may or may not apply to a specific situation. It is not meant to be exhaustive but can serve as a basis to construct the questionnaire adapted to the specific outbreak. Investigators should choose the items most relevant to their situation and should consider adding other questions that have not been presented but may be important in their context.
Objective
To estimate the prevalence of avian influenza-specific antibodies in persons exposed to avian influenza infected animals or patients, to describe the spectrum of illness, and assess epidemiologically associated risk factors for having antibodies to avian influenza.
Study design
Two types of surveys can be conducted. Prospective studies estimate the incidence of infections whereas retrospective studies estimate prevalence of past exposures to avian influenza without confirming the time when the infection occurred.
Description and source of study population and catchment areas
The target populations for the study should be defined with inclusion criteria describing the demographic characteristics of participants (age, gender, occupation, residence, etc...) and the type and timing of exposure to infected animals or patients.
Exposed and non exposed participants
Seroprevalence studies that include only a group of exposed persons are useful but may not be adequate to identify risk factors outside the direct exposure to an infected animal or patient that contributed to infection. The inclusion of a group of participants who have not been exposed to infected animals or patients will generally provide a different perspective on other factors or behaviours that contributed to infection. Therefore the enrolment of a group of non-exposed participants is generally recommendable.
Enrolment and data collection
The site of enrolment, the method to contact participants, to obtain their informed consent, to collect information and blood specimen should be described. It may be useful to plan to ask participants who have positive test results for antibody to avian influenza if they would agree to participate in follow-up studies. The follow-up could include 1) clinical information on an influenza-like illness if not yet available; 2) testing of banked sera if available for comparison of antibody titers to assist with the interpretation of test results; and/or 3) testing of an additional blood sample to assist with the interpretation of test results. The participant may choose to participate in any of the three components of the study that are applicable and may refuse to participate in any of them.
Variables
Variables to collect will vary according to the specific event. However the set of common characteristics that are interesting include: Age, sex, area of residence, primary occupation, medical history and underlying conditions, smoking habits, prior influenza vaccination, number of persons in the household, contacts with pet animals, travel, activities where contacts with animal may have occurred, household and non household contacts with a sick person, types of contacts, presence of symptoms of respiratory infection, duration of disease, medical consultation, hospitalization, outcome.
For occupational exposure, specific questions related to each activity and the protective measures used should be collected.
The sample questionnaire includes several variables collected during previous serosurveys and can serve as a starting point to develop the final questionnaire to use during a specific event. The questions have been grouped into sections that address specific issues. Some or all of these sections may be relevant during an outbreak and selection should be made accordingly. This questionnaire is not meant to be exhaustive and should be adapted to individual situation.
Laboratory methods
As the antibody response requires time to become detectable, specimens collected early after a contact may still be negative despite the presence of an ongoing infection whereas negative specimens collected ≥21 days after the last possible time of exposure rule out an infection. This concept is important for prospective studies because they will require the collection of two blood specimens: one at time of enrolment and a second one collected ≥21 days after the last possible time of exposure. Retrospective studies will collect only one specimen taken ≥21 days after the last possible time of exposure. As antibodies persist for months, a retrospective study has little risks of false negative results if conducted within six months of exposure.
The blood should be centrifuged, and serum separated, aliquoted into multiple cryovials and, labelled. If tested within a week, the serum can be kept in the refrigerator. If not tested immediately sera should be frozen at minus 20 ºC. For long term conservation, sera should be frozen at minus 70 ºC. Determination of antibodies to avian influenza can be done through a variety of assays including haemagglutination inhibition, neutralization assays including micro-neutralization and western blot (Ref: Rowe T, Abernathy RA, Hu-Primmer J, Thompson WW, Lu X, Lim W, Fukuda K, Cox NJ, Katz JM. Detection of antibody to avian influenza A (H5N1) virus in human serum by using a combination of serologic assays. Journal of Clinical Microbiology 1999;37:937-43) .
Sample size and statistical power
The precision of the estimate will vary with the expected prevalence of infection. The precision of prevalence in studies with only one group of exposed people is presented Table 1. Table 2 presents the number of participants per group required for different expected prevalence to obtain an 80% power.
| Prevalence | Precision |
|||
|---|---|---|---|---|
±1% |
± 2% |
± 5% |
± 10% |
|
| 1% | 380 |
95 |
15 |
4 |
| 5% | 1,825 |
456 |
73 |
18 |
| 10% | 3,457 |
864 |
138 |
35 |
| 15% | 4,898 |
1,225 |
196 |
49 |
| Prevalence in the exposed group |
Prevalence in the control group |
|||
|---|---|---|---|---|
1% |
2% |
3% |
5% |
|
| 5% | 332 |
653 |
1604 |
Infinite |
| 10% | 121 |
161 |
221 |
474 |
| 15% | 71 |
86 |
104 |
159 |
| 20% | 50 |
57 |
65 |
88 |
| 25% | 37 |
42 |
46 |
58 |
While in many circumstances the number of people exposed will not be sufficient to obtain precise estimates, studies will still be valuable to demonstrate if transmission appears to be efficient or small.
Statistical Analysis
The primary outcome is the seroprevalence of antibody in the exposed and non exposed groups. Risk factors should be sought comparing the characteristics of positive and negative exposed patients and comparing the exposed and unexposed participants.
Ethics
Seroprevalence studies must respect the highest ethical standards for protection of the research subject and be approved by a recognized Research Ethics Board. Signed informed consent should be obtained from each subject. In respect of the individual's privacy, a study code number must be assigned to all research participants. This will allow for confidentiality of information to be maintained to the extent legally possible. A record linking the participant's name and study code number should be kept secure and confidential by the investigator. Personal information should never be divulged to a third party and only aggregate results presented at conferences and in publications. Patients should be informed that testing will only be done for the presence of antibody to influenza and other respiratory viruses, but that under no circumstance will their sample be screened for unrelated viruses such as HIV.
The benefit of these studies is to increase knowledge concerning the risk for infection from avian influenza viruses. There may be no direct benefit to the research subject who is donating blood for these studies. If antibody is detected among participants, the study may also help determine which types of exposures are associated with an increased risk of infection. The potential discomforts and hazards of seroprevalence studies are minimal. These include risks associated with venipuncture, which may cause temporary discomfort at the procedure site. Participants should have access to contact phone numbers in the consent form in the event of adverse reactions to blood draws or general concerns during the course of the study. The participant should be free to withdraw his/her sample from the serum bank and/or participation in the study at any time after the blood is drawn.
Annex 1
Sample Questionnaire for Avian influenza serosurvey
PDF Version 
(7 Pages, 139 KB)
Appendix 2: National FluWatch
Influenza Surveillance System
Appendix 3: National SRI
Investigation
Report Form Data Elements
(please refer to form for definitions : www.phac-aspc.gc.ca)
Reporting Information
Patient Information
Surveillance definition algorithm
Clinical Information
Underling Illness
|
Travel Related
Exposure history
Laboratory Testing
|
1 Refer to the Public Health Measures, Annex M of the Canadian Pandemic Influenza Plan.
2 RIORP is an agreement between Federal/Provincial/Territorial governments to guide the operating procedures to assist in coordinating the investigation and control of severe respiratory outbreaks in Canada.
3 For a generic serosurvey protocol, refer to the following document: "Generic Serosurvey Protocol of People Exposed to Influenza", Appendix 1.
4 At the federal level, regular environmental scanning for the detectionof potentially significant influenza-like illness is conducted using official information sources for influenza surveilance (e.g. WHO and international government influenza surveillance programs) as well as unconfirmed reports from early warning systems (e.g. ProMed and other media scanning software such as the Global Public Health Intelligence Network (GPHIN)). Provinces and territories receive regular summaries of the internatinal situation through the Canadina Integrated Outbreak Surveillance Centre (CIOSC).
5 During the interpandemic phases, these data (FluWatch) will be reported on a weekly (during the influenza season) and bi-weekly (during the summer months) basis
6 The Immunization Monitoring Program ACTive (IMPACT) is a paediatric hospital-based national active surveillance network for adverse events following immunization, vaccine failures and selected infectious diseases in children that are, or are soon to be, vaccine preventable.
7 Refer to the Public Health Measures, Annex M, of the Canadian Pandemic Influenza Plan.
8 The level of enhanced surveillance will depend on the location of the first case(s) in Canada as well as the risk assessment and whether the cases arise in Canada or are imported cases and novel viruses arising in Canada.
9 Although it is considered unlikely that a pandemic strain will first emerge in Canada, the public health system needs to be prepared to deal with this possibility. Public Health Alerts need to address the situation for both impor
10 Refer to the Public Health Measures, Annex M, of the Canadian Pandemic Influenza Plan.
11 Implementation of serologic surveys can be considered at this time. Guidelines developed as a framework to be revised as needed at the time of implementation are found in appendix I. Plans for vaccine effectiveness studies should be reviewed and prepared for implementation.
12 The Immunization Monitoring Program ACTive (IMPACT) is a paediatric hospital-based national active surveillance network for adverse events following immunization, vaccine failures and selected infectious diseases in children that are, or are soon to be, vaccine preventable.
13 The Immunization Monitoring Program ACTive (IMPACT) is a paediatric hospital-based national active surveillance network for adverse events following immunization, vaccine failures and selected infectious diseases in children that are, or are soon to be, baccine preventable.
14 The Immunization Monitoring Program ACTive (IMPACT) is a paediatric hospital-based national active surveillance network for adverse events following immunization, vaccine failures and selected infectious diseases in children that are, or are soon to be, baccine preventable.
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