Alberta Health Seasonal Influenza in Alberta 2016/2017 Season Analytics and Performance Reporting Branch September 2017
For more information contact: Analytics and Performance Reporting Branch Health Standards, Quality and Performance Division Alberta Health P O Box 1360 Stn Main Edmonton, AB T5J 2N3 Email: Website: Health.Surveillance@gov.ab.ca www.health.alberta.ca Title: Seasonal Influenza in Alberta 2016/2017 Season ISSN: 2561-3154 2017 Government of Alberta 2
Executive Summary The 2016/2017 influenza season was of average intensity, crossing the seasonal threshold in week 43 and peaking in week 52. Unlike other recent seasons, the characteristics of the season varied between the zones, with Calgary Zone experiencing a more intense season with the highest number of labconfirmed cases since the 2009 pandemic and high numbers of outbreaks in long-term care facilities and supportive living sites. The rate of illness in Alberta was highest in seniors (age 65 79), the elderly (age 80+) and infants under the age of one year. The predominant circulating strain was influenza A(H3N2). The number of hospitalizations and fatalities this season was higher than the 2012/2013 season, but lower than the 2014/2015 season. Influenza immunization coverage was 27 per cent in Alberta. Introduction The predominant circulating strain in Canada was influenza A (H3N2); 98 per cent of influenza A isolates analyzed by the National Microbiology Laboratory (NML) were influenza A(H3N2) isolates that were considered genetically or antigenically similar to the vaccine strain 1 2. Of the 608 influenza B isolates analyzed, 20 per cent were of the same lineage as what was recommended for the trivalent vaccine (Victoria). The other 80 per cent were of the Yamagata lineage and thus mismatched to the trivalent vaccine, but similar to the strain recommended in the quadravalent vaccine. The majority of Albertans received a quadravalent vaccine. The components included in the 2016/2017 northern hemisphere trivalent vaccine were: Influenza A/Hong Kong/4801/2014-like virus (H3N2), Influenza A/California/07/2009(H1N1) pdm09-like virus and Influenza B/Brisbane/60/2008-like virus (Victoria lineage) 3. Influenza B/Phuket/3073/2013-like virus (Yamagata lineage) was a component of the quadravalent vaccine. The interim vaccine effectiveness estimate for Canada was 42 per cent (95% CI: 18 59%), similar to the United States, 43 per cent (95% CI: 29 54%) and imove s estimate in Europe, 38 per cent (95% CI: 21 51%). 4 5 6 This report describes the 2016/2017 influenza season in Alberta. While influenza surveillance in Alberta occurs year round, this report includes surveillance of influenza activity from August 28, 2016 (Week 35) to June 10, 2017 (Week 23) (See Appendix 1 for weeks and date ranges for the 2016/2017 season). 2017 Government of Alberta 3
Influenza Activity in Alberta The 2016/2017 influenza season was of roughly average intensity with 4,494 lab-confirmed cases of influenza (107.5 cases per 100,000), 18,443 antiviral dispense events by community pharmacists, 5,668 individuals diagnosed with influenza in emergency rooms and 20,091 individuals diagnosed in general practitioner s offices (Figures 1 4). The season started in week 43 and peaked in week 52 (see data notes for additional details on methodology); the peak for sentinel physicians was week 1 (Figures 1 and 5). Influenza A (H3N2) was the predominant circulating strain, accounting for 79 per cent of the labconfirmed cases (n=3,547); there were 27 influenza A (H1N1) lab-confirmed cases and 219 labconfirmed influenza A cases that could not be subtyped. Influenza B activity was average this year, with 701 lab-confirmed cases, the majority of which were similar to B/Phuket/3073/13 (B/Yamagata lineage) 1,2. This was part of the quadravalent influenza vaccine that was available to all children and working-age adults in Alberta; seniors received the trivalent adjuvented vaccine that contained a B/Brisbane/60/2008-like virus. Figure 1: Laboratory-confirmed cases of influenza, by subtype and week of diagnosis, as compared to the five-year seasonal average*. *The average seasonal peak has been shifted to match this season s peak to aid comparisons. See Appendix 2 for data notes. 2017 Government of Alberta 4
Figure 2: Number of individuals in physician claims diagnosed with influenza in general practitioner offices via physician claims, by season. Figure 3: Number of individuals in physician claims diagnosed with influenza in emergency departments, by season. Number of Individuals Number of Individuals 2017 Government of Alberta 5
Figure 4: Number of antiviral prescriptions dispensed by pharmacists, by week. Figure 5: Per cent of patient visits due to influenza-like illness as reported by sentinel physicians, by week and season. Per cent Influenza-like Illness (ILI) Number of prescriptions 2017 Government of Alberta 6
Alberta Health Service Zone This season Calgary Zone had the highest number of lab-confirmed cases (1,751) and Central Zone had the most cases per capita with a rate of 135.8 cases per 100,000 (Table 1). The number of labconfirmed cases in Calgary Zone was the highest recorded since the 2009 pandemic. While the zones usually peak at approximately the same time (Figure 7), the timing of the influenza season was much earlier in Calgary Zone as compared to the other zones (Figure 6). Calgary Zone peaked in week 49, South Zone in week 52, Edmonton Zone in week 1, Central Zone in week 1, and North Zone in week 3. Table 1: Rate of laboratory-confirmed influenza cases by Zone (per 100,000 population). 2016/2017 2015/2016 2014/2015 2013/2014 2012/2013 Count Rate Count Rate Count Rate Count Rate Count Rate North 467 96.4 845 174.5 658 137.1 997 66.2 327 71.4 Edmonton 1269 95.3 1566 117.6 1564 120.0 621 133.5 1092 89.5 Calgary 1751 110.3 1700 107.1 1612 103.7 1365 108.2 781 53.7 Central 645 135.8 772 162.5 667 141.5 692 147.2 373 81.5 South 361 120.1 424 141.0 355 118.8 238 80.7 315 107.9 Alberta 4494* 107.5 5307 127.0 4858* 118.2 3913 97.9 2888 74.4 * Zone unavailable for one case in 2016/2017 and two cases in 2014/2015 Age The rate of illness was highest in the elderly and lower in children and working age adults (Figure 8, Table 2). The rate in the elderly was 2.4 times higher this season than the 2012/2013 season (829.4 per 100,000 population versus 346.4 per 100,000), but not as high as the 2014/2015 season when the influenza vaccine had exceedingly low vaccine effectiveness (1097.0 per 100,000). The higher rate of illness in the elderly this season may be due to the high number of outbreaks in long-term care facilities and supportive living facilities that Calgary Zone experienced. 2017 Government of Alberta 7
Figure 6: Number of lab-confirmed influenza cases in 2016/2017, by week of diagnosis and zone. Number of Cases Figure 7: Number of lab-confirmed influenza cases, week of diagnosis, zone and season. 2015/2016 2014/2015 2013/2014 2012/2013 2017 Government of Alberta 8
Figure 8: Rate of laboratory-confirmed influenza infections by age and season (per 100,000). Rate per 100,000 Table 2: Rate of laboratory-confirmed influenza infections by age and season (per 100,000). 2016/2017 2015/2016 2014/2015 2013/2014 2012/2013 Count Rate Count Rate Count Rate Count Rate Count Rate 0 11 months 115 201.9 237 416 156 281.1 241 450.2 167 325.8 1 4 years 266 122.9 603 278.6 371 174.7 436 209.1 422 206 5 9 years 212 81.2 481 184.3 319 126.4 194 80.1 243 105.2 10 14 years 160 68.8 235 101.1 193 84.4 104 46.1 140 62.8 15 19 years 197 80.9 176 72.3 149 60.7 120 48.8 77 31.3 20 24 years 164 56.3 223 76.6 146 49.7 180 62.2 91 32.1 25 34 years 393 55.6 724 102.4 351 50.5 601 90 289 45.1 35 54 years 744 62.9 1301 109.9 734 62.5 1059 91.9 520 46 55 64 years 494 98.7 617 123.3 404 83.7 483 104.4 273 61.7 65 79 years 726 199.1 486 133.3 718 206.3 305 91.9 274 87.3 80+ years 1019 829.4 222 180.7 1317 1097.6 190 162.6 392 346.4 Total 4,494* 107.5 5,307* 127.0 4,858 118.2 3,913 97.9 2,888 74.4 * Age unavailable for four cases in 2016/2017 and two cases in 2015/2016 2017 Government of Alberta 9
Outbreaks Outbreaks are defined as the occurrence of a communicable disease in a community, region or setting where the number of cases is more than would be expected for a defined period of time 7. Influenza outbreaks in hospitals, residential institutions and other closed communities are defined as two or more cases of influenza-like-illness, at least one of which is a lab-confirmed case 8. School influenza outbreaks require greater than 10 per cent absenteeism or absenteeism that is 10 per cent higher than baseline levels 8. Influenza outbreaks that occur in group settings such as hospitals, residential institutions, schools, and child care facilities are reported to Alberta Health. There were 187 influenza outbreaks reported to Alberta Health this season, almost twice as many as the 2012/2013 season, but 25 per cent fewer than the 2014/2015 season where that season s vaccine was found to have poor effectiveness against the predominant circulating strain (Figure 9 and Table 3). This pattern was similar across zones, with the exception of Calgary. Calgary reported 66 outbreaks in 2016/2017, one more than the 65 outbreaks reported in 2014/2015 (Figure 10). The majority of outbreaks were in long-term care facilities and supportive living sites. Figure 9: Number of lab-confirmed influenza outbreaks reported in Alberta, by season and outbreak site. 2017 Government of Alberta 10
Figure 10: Number of lab-confirmed influenza outbreaks reported by zone, season and outbreak site. Legend 2017 Government of Alberta 11
Table 3: Count of outbreaks by setting and season. 2016/2017 2015/2016 2014/2015 2013/2014 2012/2013 Count Per Per Per Per Per Count Count Count Count cent cent cent cent cent Acute Care Facility 29 16% 11 19% 20 8% 11 22% 14 14% Child Care Facility 0 0% 1 2% 0 0% 5 10% 4 4% Correctional Facility 2 1% 4 7% 5 2% 6 12% 1 1% Long Term Care Facility 84 45% 21 36% 113 47% 19 37% 42 42% Other, Specify 1 1% 2 3% 2 1% 1 2% 0 0% School (K-12) 5 3% 4 7% 13 5% 2 4% 10 10% Supportive Living/Home Living 66 35% 15 26% 90 37% 7 14% 29 29% Sites Total 187 58 243 51 100 Hospitalized Cases There were 1,653 hospitalizations, 109 ICU admissions and 54 fatalities (where influenza caused or contributed to the death of a hospitalized influenza patient), for a rate of 39.6 per 100,000, 2.6 per 100,000 and 1.3 per 100,000 respectively (Table 4). Consistent with the rate of lab-confirmed illness, the rates of hospitalizations and fatalities were lower this season than the 2014/2015 season where the vaccine had low effectiveness, but higher than the 2012/2013 season (Figure 11). As to be expected in an influenza A(H3N2)-predominant year, the rate of hospitalizations was highest in seniors and the elderly, followed by infants under the age of one (Figure 12). Notably, the age distribution of hospitalizations and fatalities was more similar to the 2014/2015 season (when the vaccine was not effective) than the 2012/2013 season (the previous influenza A(H3N2)- predominant season). This may be associated with the high number of outbreaks in long-term care facilities and supportive living sites in Calgary Zone. 2017 Government of Alberta 12
Table 4: Rate per 100,000 of lab-confirmed influenza hospitalizations, ICU admissions, and hospitalized fatalities by season. Season Hospitalization Rate (95% CI) ICU Admission Rate (95% CI) Fatalities Rate (95% CI) 2012/2013 25.0 (23.4 26.5)* 3.9 (3.3 4.5)* 1.0 (0.6 1.3) 2013/2014 30.0 (28.3 31.7)* 5.4 (4.7 6.2)* 0.7 (0.5 1.0) 2014/2015 46.7 (44.7 48.8)* 4.1 (3.5 4.7)* 2.3 (1.8 2.8)* 2015/2016 41.7 (39.7 43.6) 6.6 (5.8 7.3)* 1.3 (1.0 1.7) 2016/2017 39.6 (37.7 41.5) 2.6 (2.2 3.1) 1.3 (1.0 1.7) *Statistically significant different than 2016/2017 (p< 0.05). Influenza A(H3N2)-predominant seasons: 2012/2013, 2014/2015, 2016/2017 Influenza A(H1N1)pdm09 predominant seasons: 2013/2014, 2015/2016 Figure 11: Number of influenza fatalities by season. 2017 Government of Alberta 13
Figure 12. Rate of hospitalized influenza cases by age group and season (per 100,000). Antiviral Resistance As of August 24, 2017, the NML had tested 2,340 influenza viruses (129 from Alberta) for resistance to the antiviral drugs oseltamivir, zanamivir, and amantadine 9,10,11. Similar to last season, all influenza isolates were sensitive to zanamivir, 99 per cent of isolates were sensitive to oseltamivir, and all influenza A isolates were resistant to amantadine. Three isolates were resistant to oseltamivir, none of which were isolated in Alberta. Influenza Immunization The seasonal influenza vaccination program is universal in Alberta. 1,171,825 influenza immunizations were given to Albertans in the 2016/2017 season; influenza immunization coverage is 27 per cent (Table 5). The majority of influenza immunizations were given by pharmacists (45%) and AHS public health (35%) (Figures 13 and 14). 2017 Government of Alberta 14
Table 5: Doses of influenza vaccine administered and coverage, by season. Season Number of Immunizations Per cent of Albertans Immunized 2012/2013 919,348 24% 2013/2014 1,157,550 29% 2014/2015 1,254,950 30% 2015/2016 1,146,569 27% 2016/2017 1,171,825 27% Figure 13. Number of dose of influenza vaccine administered by provider and season. 2017 Government of Alberta 15
Figure 14. Proportion of influenza immunizations administered by provider, by season. Conclusion The 2016/2017 season in Alberta was average for most zones, but of higher intensity in Calgary Zone where there were above average numbers of lab-confirmed cases and outbreaks in long-term care facilities and supportive living sites. Influenza A(H3N2) predominated, with increased rates of illness in seniors, the elderly and infants. Studies in other jurisdictions found the influenza vaccine to be 42 per cent effective against influenza A(H3N2) this season 4. This was reflected in the number of hospitalizations and fatalities; they were lower than the 2014/2015 season when the vaccine was found to have low effectiveness. Influenza immunization coverage continues to be 27 per cent in Alberta. Acknowledgements We would like to thank the Provincial Laboratory for Public Health (ProvLab), Alberta Health Services (AHS), First Nations Inuit Health Branch (FNIHB), the National Microbiology Laboratory (NML), Alberta Blue Cross, and TARRANT Viral Watch sentinel physician system for their partnership in influenza surveillance in Alberta. 2017 Government of Alberta 16
Appendix 1: 2016/2017 Influenza Season Reporting Weeks Week Start End Week Start End 35 28-Aug-16 03-Sep-16 9 26-Feb-17 04-Mar-17 36 04-Sep-16 10-Sep-16 10 05-Mar-17 11-Mar-17 37 11-Sep-16 17-Sep-16 11 12-Mar-17 18-Mar-17 38 18-Sep-16 24-Sep-16 12 19-Mar-17 25-Mar-17 39 25-Sep-16 01-Oct-16 13 26-Mar-17 01-Apr-17 40 02-Oct-16 08-Oct-16 14 02-Apr-17 08-Apr-17 41 09-Oct-16 15-Oct-16 15 09-Apr-17 15-Apr-17 42 16-Oct-16 22-Oct-16 16 16-Apr-17 22-Apr-17 43 23-Oct-16 29-Oct-16 17 23-Apr-17 29-Apr-17 44 30-Oct-16 05-Nov-16 18 30-Apr-17 06-May-17 45 06-Nov-16 12-Nov-16 19 07-May-17 13-May-17 46 13-Nov-16 19-Nov-16 20 14-May-17 20-May-17 47 20-Nov-16 26-Nov-16 21 21-May-17 27-May-17 48 27-Nov-16 03-Dec-16 22 28-May-17 03-Jun-17 49 04-Dec-16 10-Dec-16 23 04-Jun-17 10-Jun-17 50 11-Dec-16 17-Dec-16 24 11-Jun-17 17-Jun-17 51 18-Dec-16 24-Dec-16 25 18-Jun-17 24-Jun-17 52 25-Dec-16 31-Dec-16 26 25-Jun-17 01-Jul-17 1 01-Jan-17 07-Jan-17 27 02-Jul-17 08-Jul-17 2 08-Jan-17 14-Jan-17 28 09-Jul-17 15-Jul-17 3 15-Jan-17 21-Jan-17 29 16-Jul-17 22-Jul-17 4 22-Jan-17 28-Jan-17 30 23-Jul-17 29-Jul-17 5 29-Jan-17 04-Feb-17 31 30-Jul-17 05-Aug-17 6 05-Feb-17 11-Feb-17 32 06-Aug-17 12-Aug-17 7 12-Feb-17 18-Feb-17 33 13-Aug-17 19-Aug-17 8 19-Feb-17 25-Feb-17 34 20-Aug-17 26-Aug-17 2017 Government of Alberta 17
Alberta Health, Surveillance and Assessment Seasonal Influenza in Alberta, 2016/2017 Summary Report August 2016 Appendix 2: Data Notes Data Sources: Alberta Health Care Insurance Plan (AHCIP) Quarterly Population Registry, Alberta Health Communicable Disease Reporting System (CDRS), Alberta Health Immunization/Adverse Reactions to Immunization (Imm/ARI), Alberta Health Alberta Blue Cross TARRANT Viral Watch Sentinel Physician Network Supplemental Enhanced Service Event (Physician Claims), Alberta Health Pharmaceutical Information Network (PIN), Alberta Health Defining Thresholds for Lab-Confirmed Influenza Surveillance An important function of influenza surveillance is to determine whether the timing or magnitude of the influenza season is unusual compared to previous seasons. The World Health Organization recommends comparing current-season influenza activity to the average epidemic curve, and to create two thresholds one to determine when the influenza season has begun (seasonal threshold) and to determine at what point current influenza activity would be unusually high (alert threshold) 1. The average epidemic curve for lab-confirmed influenza surveillance was estimated using data collected between the 2010/2011 and 2014/2015 seasons. Lab-confirmed influenza became routinely reported in 2009; however, the 2009/2010 pandemic season was excluded. The peaks of each season were aligned, and the average number of cases reported per aligned week was calculated as well as the 90 per cent confidence limit. The 90 per cent confidence limit acts as the Alert Threshold. If the number of cases reported in a week passes this threshold it is considered to be unusually high. Until the current season has peaked, the best estimate of the peak is utilized to align the current season to the average epidemic curve. The first estimate utilized was the median of the previous five seasons, week 2. The seasonal threshold was estimated as the average number of cases reported per week, in weeks considered outside of the influenza season (i.e., pre-season weeks). The start of the influenza epidemic was defined as the week in which the per cent positivity of influenza A laboratory tests at ProvLab were 10 per cent of all respiratory laboratory tests ordered that week 2. The end of the influenza epidemic was defined as the week in which the per cent positivity of influenza B was < 10 per cent of all respiratory laboratory tests ordered that week 2. All weeks in between these time periods were considered part of the influenza epidemic. Per cent positivity is an accepted method of determining the influenza season 1, however visual inspection was also utilized to ensure face validity. 1 World Health Organization 2013 Global Epidemiological Surveillance Standards for Influenza. Geneva. http://www.who.int/influenza/resources/documents/influenza_surveillance_manual/en/ 2 Provincial Laboratory for Public Health (ProvLab) Weekly Respiratory Summary 2017 Government of Alberta 18
The start of the influenza season was defined as the third consecutive week where the number of lab-confirmed cases was above the seasonal threshold; the end of the influenza season was defined as the third consecutive week where the number of lab-confirmed cases was below the seasonal threshold. Figure 1 Laboratory-confirmed cases of influenza, by subtype and week of diagnosis. To ensure consistency in graphing between seasons, cases diagnosed in week 53 in the 2014/2015 season (December 28, 2014 January 3, 2015) were placed into week 52 or week 1. This makes the peak of the influenza season appear to be week 52, although the number of lab-confirmed cases was slightly higher in week 51 than week 52. 2017 Government of Alberta 19
References 1 National Medical Laboratory (NML), 2017 NML Genetic Characterization on H3N2 Influenza Isolates in Canada September 1, 2016to July 20, 2017. Influenza and Respiratory Viruses Section, National Medical Laboratory, Public Health Agency of Canada. 2 National Medical Laboratory (NML), 2017 NML Strain Characterization Completed on Influenza Isolates in Canada September 1, 2016to July 20, 2017. Influenza and Respiratory Viruses Section, National Medical Laboratory, Public Health Agency of Canada. 3 World Health Organization (WHO) 2016 Recommended composition of influenza virus vaccines for use in the 2016-2017 northern hemisphere influenza season. Accessed July 27, 2017. http://www.who.int/influenza/vaccines/virus/recommendations/2016_17_north/en/ 4 Skowronski, D. et al. 2017 Interim estimates of 2016/17 vaccine effectiveness against influenza A(H3N2), Canada, January 2017. Euro Surveill. 2017;22(6): pii=30460. DOI: http://dx.doi.org/10.2807/1560-7917.es.2017.22.6.30460 5 Kissling, E. et al. 2017. Early 2016/17 influenza vaccine effectiveness estimates against influenza A(H3N2): I-MOVE multicenter case-control studies at primary care and hospital levels in Europe. Euro Surveill. 2017;22(7):pii=30464. DOI: http://dx.doi.org/10.2807/1560-7917.es.2017.22.7.30464 6 Flannery, B et al. 2017 Interim estimates of 2016-17 seasonal influenza vaccine effectiveness United States, February 2017. MMWR 66(6):167-171. 7 Alberta Health. 2014. Epidemics Case Definition, Public Health Notifiable Disease Management Guidelines. Accessed August 3, 2017. https://open.alberta.ca/dataset/3c818519-ea4e-433f-a5f9-508fab363664/resource/3a854ab6-f913-46a3-95a2-958cdb00591c/download/guidelines-epidemics-2014.pdf 8 Alberta Health. 2014. Influenza Case Definition, Public Health Notifiable Disease Management Guidelines. Accessed August 3, 2017. https://open.alberta.ca/dataset/62c6352f-fd9e-4c42-9867- 9f2b142b6eff/resource/b872e3e2-f8b0-4716-8089-c17e201c69c9/download/Guidelines-Influenza-2014.pdf 9 National Medical Laboratory (NML), 2017 NML Oseltamivir Susceptibility Assay Completed on Influenza Isolates in Canada September 1, 2016 to August 24, 2017. Influenza and Respiratory Viruses Section, National Medical Laboratory, Public Health Agency of Canada. 10 National Medical Laboratory (NML), 2017 NML Zanamivir Susceptibility Assay Completed on Influenza Isolates in Canada September 1, 2016 to August 24, 2017. Influenza and Respiratory Viruses Section, National Medical Laboratory, Public Health Agency of Canada. 11 National Medical Laboratory (NML), 2017 NML Amantadine Susceptibility Assay Completed on Influenza Isolates in Canada September 1, 2016 to August 24, 2017. Influenza and Respiratory Viruses Section, National Medical Laboratory, Public Health Agency of Canada. 2017 Government of Alberta 20