Preparing for uncertainty during public health emergencies: What Canadian health leaders can do now to optimize future emergency response.

It is clear that the risk for epidemics with high health and socio-economic impacts remains but there will be many unknowns at the start of future responses to these events. This article highlights principles and practices to assist health leaders in preparing for uncertainty, including integrating scalability to ensure response activities can be more easily adapted to suit evolving needs; assessing risk and capabilities to inform planning for appropriate response measures; and considering overall flexibility and adaptability of plans, systems, and resources. Ultimately, being prepared for "Disease X" is about applying the approaches that we have learned from previous events, using evidence-based practices to develop and strengthen foundational capacities, so that we are able to respond to the unanticipated in proportionate and appropriate ways.

Intranasal influenza vaccine: Why does Canada have different recommendations from the USA on its use?

Canada and the USA differ in their recommendations for the use of live attenuated influenza vaccine (LAIV). The Canadian National Advisory Committee on Immunization (NACI) continues to recommend LAIV as one of the influenza vaccines available for use in children 2 to 17 years of age. The US Advisory Committee on Immunization Practices (ACIP) made an interim recommendation against the use of LAIV for the 2016 to 2017 influenza season in response to low LAIV effectiveness observed in the USA during the 2013 to 2014 to 2015 to 2016 seasons. The recommendation has been continued for the 2017 to 2018 season. In response, NACI undertook a review of available LAIV effectiveness data in children and adolescents from Canada, the USA and a number of European countries. This commentary by Canada's Chief Public Health Officer summarizes the findings of that review and provides the rationale for Canada's current continued recommendation for LAIV use.

Protective measures and human antibody response during an avian influenza H7N3 outbreak in poultry in British Columbia, Canada.

BACKGROUND: In 2004 an outbreak of avian influenza of the H7N3 subtype occurred among poultry in British Columbia, Canada. We report compliance with recommended protective measures and associated human infections during this outbreak. METHODS: We sought voluntary participation by anyone (cullers, farmers and their families) involved in efforts to control the poultry outbreak. Recruitment was by advertisements at the worker deployment site, in local media and through newsletters sent directly to farmers. Sera were tested for antibody to H7N3 by microneutralization assay. A subset of 16 sera (including convalescent sera from 2 unprotected workers with conjunctivitis from whom virus had been isolated) was further tested by Western blot and routine and modified hemagglutination inhibition assays. RESULTS: A total of 167 people (20% to 25% of all workers) participated between May 7 and July 26, 2004. Of these, 19 had experienced influenza-like illness and 21 had experienced red or watery eyes. There was no significant association between illness reports and exposure to infected birds. Among 65 people who entered barns with infected birds, 55 (85%) had received influenza vaccine, 48 (74%) had received oseltamivir, and 55 (85%), 54 (83%) and 36 (55%) reported always wearing gloves, mask or goggles, respectively. Antibody to the H7 subtype was not detected in any sera. INTERPRETATION: During the BC outbreak, compliance with recommended protective measures, especially goggles, was incomplete. Multiple back-up precautions, including oseltamivir prophylaxis, may prevent human infections and should be readily accessible and consistently used by those involved in the control of future outbreaks of avian influenza in poultry. Localized human avian influenza infections may not result in serologic response despite confirmed viral detection and culture.

Influenza-attributed hospitalization rates among pregnant women in Canada 1994-2000.

BACKGROUND: Although it is recommended that pregnant women at risk for influenza complications receive influenza vaccine, it is not clear if healthy pregnant women are at increased risk for adverse outcomes. We aimed to estimate the rate of hospitalization attributable to influenza for healthy pregnant women and for those with known co-morbidities. METHODS: Hospital admission records of women admitted from 1994 to 2000 with a respiratory condition during pregnancy were extracted from the hospitalization database (Canadian Institute of Health Information). Admissions for childbirth were excluded. Weekly admissions, stratified by the presence of co-morbid conditions, were modelled as a function of viral activity, seasonality, trend, and holiday effects using Poisson regression with proxies for influenza and other viral activity developed previously for similar age-specific models of influenza-attributed hospital admissions. RESULTS: Approximately 300 hospitalizations of pregnant women per year were attributed to influenza, of which 140 were in women with co-morbidities. This hospitalization rate corresponds to 150 (95% CI 140-170) hospitalizations per 100,000 pregnant women per year. An estimated 1 in 1000 healthy pregnant women were hospitalized due to influenza per year. Asthma was the most important risk factor, accounting for an estimated 450 (95% CI 300-600) admissions per 100,000 pregnant women. Admission rates in pregnant women were relatively constant across multiple influenza seasons of varying severity among older adults. During the four weeks of peak influenza activity, 60% of respiratory-related admissions of otherwise healthy pregnant women could be attributed to influenza. CONCLUSION: Healthy pregnant Canadian women have consistently higher rates of hospital admission attributable to influenza infection than their non-pregnant peers. The admission rate for healthy pregnant women corresponds to the rate for men and women aged 65 to 69 years, which suggests that this population may benefit from annual influenza immunization.

Hospitalization attributable to influenza and other viral respiratory illnesses in Canadian children.

BACKGROUND: We sought to estimate the incidence of hospitalization attributable to influenza virus infection in Canadian children while controlling for the impact of other respiratory viruses. METHODS: Hospital admissions for children and youth 0 to 19 years of age, 1994-2000, were modeled as a function of proxy variables for influenza, respiratory syncytial virus (RSV) and other respiratory viral activity, seasonality and trend, using a Poisson regression model with a linear link. These proxy variables were developed from influenza mortality and laboratory test results for influenza, RSV and other viruses. Various checks for consistency, model fit and robustness were conducted and guided model development. RESULTS: Overall, 1.5% of all pediatric respiratory admissions could be attributed to influenza (18 admissions per 100,000 per year). The largest burden was seen in infants 6 to 11 months of age with rates of 200 per 100,000 infants and approximately equivalent to the rate for adults aged 65 to 69. During peak influenza activity, 7% of respiratory admissions were attributable to influenza as were 35% of febrile seizure admissions. RSV and parainfluenza (PIV) were the major viral causes of hospital admission with rates of 130 and 160 per 100,000, respectively. Another 70 per 100,000 admissions were attributed to other influenza-like illnesses. CONCLUSIONS: Influenza is a significant cause of morbidity leading to hospitalization in Canadian children, particularly for those under 2 years of age. RSV, PIV and other respiratory viruses were found to be major causes of respiratory illness leading to hospital care, surpassing influenza.

A composite epidemic curve for seasonal influenza in Canada with an international comparison.

BACKGROUND: Empirical data on laboratory-confirmed seasonal influenza is limited by very low and possibly non-systematic case ascertainment as well as geographical variation. OBJECTIVE: To provide a visual representation of an influenza epidemic at the community and regional level using empirical data and to describe the epidemic characteristics. METHODS: Weekly influenza A confirmations were obtained from the Canadian FluWatch program and American FluView program for the 1997/1998-2006/2007 seasons; 1- year data were also available for Europe (FluNet, WHO). For seasons where at least 80% of the influenza A strains were antigenically similar, a composite epidemic curve was created by centring the local epidemics relative to their epidemic midpoint. RESULTS: The range in timing of the regional peaks varied from 5 to 13 weeks. Once the epidemic curves were centred relative to their peak, the composite epidemic curves were similar for Canada, the United States and Europe, and the epidemic growth rates were similar for most subgroups (city size; regions; H1N1 versus H3N2 seasons). During the exponential growth period, the number of cases increased by a factor of 1.5-2.0 per week, averaging 1.8. Exponential growth was evident approximately 10 weeks before the peak. Evidence of sustained transmission occurred from mid-September to early June. DISCUSSION: The shape of the composite curve created in this study clearly demonstrates a consistency in the epidemic pattern across geographically disparate locales. Laboratory confirmation will likely play an increasing role in the development of better methods for early detection and summary measures of influenza activity.

Estimating sensitivity of laboratory testing for influenza in Canada through modelling.

BACKGROUND: The weekly proportion of laboratory tests that are positive for influenza is used in public health surveillance systems to identify periods of influenza activity. We aimed to estimate the sensitivity of influenza testing in Canada based on results of a national respiratory virus surveillance system. METHODS AND FINDINGS: The weekly number of influenza-negative tests from 1999 to 2006 was modelled as a function of laboratory-confirmed positive tests for influenza, respiratory syncytial virus (RSV), adenovirus and parainfluenza viruses, seasonality, and trend using Poisson regression. Sensitivity was calculated as the number of influenza positive tests divided by the number of influenza positive tests plus the model-estimated number of false negative tests. The sensitivity of influenza testing was estimated to be 33% (95%CI 32-34%), varying from 30-40% depending on the season and region. CONCLUSIONS: The estimated sensitivity of influenza tests reported to this national laboratory surveillance system is considerably less than reported test characteristics for most laboratory tests. A number of factors may explain this difference, including sample quality and specimen procurement issues as well as test characteristics. Improved diagnosis would permit better estimation of the burden of influenza.

Role of influenza and other respiratory viruses in admissions of adults to Canadian hospitals.

OBJECTIVE: We sought to estimate age-specific hospitalization rates attributed to influenza and other virus for adults. METHODS: Admissions from Canada's national hospitalization database (Canadian Institute of Health Information), from 1994/95 to 1999/2000, were modeled as a function of proxy variables for influenza, respiratory syncytial virus (RSV) and other viral activity, seasonality and trend using a Poisson regression model and stratified by age group. RESULTS: The average annual influenza-attributed hospitalization rate for all adults, 20 years of age or older, over the study period, which included three severe seasons, was an estimated 65/100,000 population (95% CI 63-67). Among persons aged 65 and over, 270-340 admissions per 100,000 population per year were attributed to influenza, while 30-110, 60-90 and 130-350 per 100,000 were attributed to RSV, parainfluenza (PIV) and other respiratory viruses, respectively. Although marked season-to-season variation in age-specific hospitalization rates attributable to influenza was observed in persons 50 years of age and older, increasing risk with age was preserved at all time periods. CONCLUSIONS: Influenza, RSV, PIV and other respiratory viruses were all associated with morbidity requiring hospitalization, while influenza was responsible for peak respiratory admissions. The burden of health care utilization associated with respiratory viruses is appreciable beginning in the sixth decade and increases significantly with age.

Co-morbidities associated with influenza-attributed mortality, 1994-2000, Canada.

The elderly and persons with specific chronic conditions are known to face elevated morbidity and mortality risks resulting from an influenza infection, and hence are routinely recommended for annual influenza vaccination. However, risk-specific mortality rates have not been established. We estimated age-specific influenza-attributable mortality rates stratified by the presence of chronic conditions and type of residence based on deaths of persons who were admitted to hospital with a respiratory complication captured in our national database. The majority of patients had chronic heart or respiratory conditions (80%) and were admitted from the community (80%). Influenza-attributable mortality rates clearly increase with age for all risk groups. Our influenza-specific estimates identified higher risk ratios for chronic lung or heart disease than have been suggested by other methods. These estimates identify groups most in need of improved vaccines and for whom the use of additional strategies, such as immunization of household contacts or caregivers should be considered.

Border screening for SARS.

With the rapid international spread of severe acute respiratory syndrome (SARS) from March through May 2003, Canada introduced various measures to screen airplane passengers at selected airports for symptoms and signs of SARS. The World Health Organization requested that all affected areas screen departing passengers for SARS symptoms. In spite of intensive screening, no SARS cases were detected. SARS has an extremely low prevalence, and the positive predictive value of screening is essentially zero. Canadian screening results raise questions about the effectiveness of available screening measures for SARS at international borders.

The Canadian Pandemic Influenza Plan: an evolution to the approach for national communicable disease emergencies.

Advance planning for a large-scale and widespread health emergency is required to optimize health care delivery during an influenza pandemic. The Canadian Pandemic Influenza Plan (CPIP) is an example of a successful communicable disease emergency plan that ensures a national, coordinated approach to preparedness, response and recovery activities in the event of an influenza pandemic. The general concepts incorporated into the CPIP may be utilised in the contingency planning for a bioterrorism event or other communicable disease emergencies, including: a national, coordinated approach in planning; an emergency management structure to conduct the response; the use of common terminology to facilitate communication and response coordination, and the establishment of specific technical, communications and operational response groups and networks in advance. The multinational outbreak of Severe Acute Respiratory Syndrome (SARS) in 2003 offered the opportunity for the testing of these concepts. The experiences and lessons learnt during the SARS response may be utilised to strengthen communicable disease preparedness and response capacity.

Factors influencing childhood influenza immunization.

Following the launch of a publicly funded influenza immunization program for all residents of Ontario over the age of 6 months, we evaluated 203 parents of children who presented to our emergency department between January and March of the following year (2001). Overall, 54 (27%) of the children had been vaccinated. Parents of non-immunized children were more likely to believe that immunization resulted in a flu-like illness (42% v. 17%; p = 0.001), caused side effects that were more severe than having influenza (36% v. 17%; p = 0.010) and weakened the immune system (52% v. 24%; p < 0.001). Parents of both immunized and non-immunized children incorrectly identified gastrointestinal symptoms as symptoms of influenza. The primary reason for deciding against immunization was the belief that their child was not at risk. After adjustment, children with a chronic disease were more likely than those without a chronic disease to be immunized (adjusted odds ratio [OR] 4.7, 95% confidence interval [CI] 1.8-12.6). Children of parents who discussed immunization with a physician were more likely to be immunized than those who had not discussed immunization with a physician (OR 6.8, 95% CI 2.4-19.2).