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Durham Region Influenza Bulletin: 2018/19 Influenza Season Summary (August 26, 2018 to August 24, 2019)

Table 1: Influenza activity in Durham Region Measure Summary of Measure

Laboratory Confirmed Cases1

(Table 2, Figures 1 & 2)

There were 455 lab confirmed cases of influenza in the 2018/19 influenza season, similar to the previous two seasons (455 in 2017/18 and 418 in 2016/17). There were 420 cases of influenza A with peaks in late December 2018 and mid-January 2019; 27 (six per cent) of these cases were H3, 43 (10 per cent) were H1N1, and 350 (83 per cent) were untyped or indeterminate. There were 34 cases of influenza B with a peak in early May 2019. There was a lower proportion of all flu cases that were influenza B (seven per cent) compared to last season (44 per cent), but similar to the 2016/17 season (nine per cent).

Age Specific Rates of Confirmed Cases (Figure 3)

Influenza rates were higher among Durham Region older adults and children compared to other age groups, but lower than Ontario for most age groups. There were 162 cases of influenza among Durham Region older adults aged 80 and older with a higher rate among males than females. There were 51 cases of influenza among Durham Region children aged 0 to 4 years with a higher rate among females than males.

Hospitalizations Among Lab Confirmed Cases2 (Figures 4 & 5)

The number of hospitalizations among lab confirmed cases was similar (267) compared to the previous season (268 in 2017/18) but significantly higher than the 2016/17 season (148). This increase may be due to a change in the respiratory virus lab testing algorithm during the 2017/18 season. The proportion of hospitalizations was slightly higher among males (53 per cent) compared to females (47 per cent). The majority of hospitalizations were among adults aged 50 years and older (58 per cent). Hospitalizations peaked in early and mid-January 2019.

Respiratory Outbreaks in Institutions3

(Figures 6 & 7)

There were fewer respiratory outbreaks in Durham Region institutions (42) compared to previous seasons (58 in 2017/18 and 68 in 2016/17). About one third (13 or 31 per cent) of these outbreaks were confirmed influenza, which is less than in the previous two seasons (26 or 45 per cent in 2017/18 and 24 or 35 per cent in 2016/17). Institutional outbreaks occurred throughout the season with a peak in mid-January 2019.

Child Absenteeism Due to Illness Reported by Child Care Centres4

(Figure 8)

Child absenteeism at child care centres peaked in mid December 2018 at 3.5 per cent. This is lower than the peak in the previous flu season (4.6 per cent) in early February 2018.

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Measure Summary of Measure

Respiratory Outbreaks in Child Care Centres5

(Figures 9 & 10)

Child care centres in Durham Region are required to report suspected disease outbreaks to the Health Department. There were more respiratory outbreaks reported in child care centres (33) compared to the 2017/18 season (24) and the 2016/17 season (11). Child care centre outbreaks peaked in mid November 2018 and in late January 2019.

Elementary School Absenteeism Due to Illness Reported by Selected Durham Region School Boards6

(Figure 11)

Rates of absenteeism due to illness at Durham Region schools were similar to previous years. Rates peaked at 3.8 per cent in late January 2019, similar to the rates in previous years at this time and similar to the average peak in previous seasons of 4.6 per cent in early February 2018 and 4.6 per cent in late January 2017.

Emergency Department Visits for Fever/Influenza-Like Illness (ILI)7

(Figure 12)

The per cent of emergency department visits for fever/Influenza-Like-Illness (ILI) peaked in late December 2018 at 7.1 per cent, which is higher than the peak in previous seasons of 5.2 per cent in early February 2018 and 4.4 per cent in late December 2016.

Adults (18+) Who Had a Flu Shot this Flu Season8

(Figures 13 & 14)

A similar proportion (46 per cent) of adults reported getting a flu shot in the 2018/19 season compared to the 2017/18 season (48 per cent) and the 2016/17 season (42 per cent). Immunization rates were higher among adults 65 years and older (68 per cent) compared to adults aged 18-64 years (30 per cent). Rates decreased slightly among adults aged 18-64 years from 37 per cent in 2017/18, but were similar to previous years.

Influenza Immunization Rates Among Long-Term Care Home (LTCH) and Hospital Staff9 (Figure 15)

Immunization rates were lower among hospital staff in Durham Region compared to Ontario. Rates were similar among LTCH staff in Durham Region compared to Ontario. Overall, rates are higher among LTCH staff compared to hospital staff in Durham Region and Ontario. Immunization rates among LTCH and hospital staff in Durham Region and Ontario increased between the 2009/10 and 2014/15 seasons but have remained stable since then.

1. The Health Protection and Promotion Act (HPPA) requires physicians, nurses and certain other health professionals to report all cases of influenza. These health professionals commonly identify cases of influenza through laboratory test results. There may be considerable under-reporting of cases because an infected person with mild or no clinical symptoms may not seek medical care and/or health professionals may not order laboratory testing.

2. Beginning in the 2017/18 influenza season, only hospital inpatients in an Intensive Care Unit or Critical Care Unit and patients in institutions such as long-term care homes are tested for influenza, as specified in Public Health Ontario’s Respiratory Virus Testing Algorithm.

3. Institutions in Durham Region, including hospitals, LTCHs and retirement homes, are required to report suspected outbreaks to the Durham Region Health Department (DRHD).

4. A sample of 13 child care centres in Durham Region voluntarily report child absenteeism due to illness on a weekly basis. Response rates vary by week.

5. All licensed child care centres in Durham Region are required under the HPPA to report suspected disease outbreaks to DRHD.

6. Durham District School Board, Kawartha Pine Ridge District School Board, and Peterborough Victoria Northumberland and Clarington Catholic District School Board report absenteeism due to illness to DRHD on a weekly basis.

7. The Acute Care Enhanced Surveillance (ACES) system collects emergency department and hospital admissions data from participating hospitals. ACES classifies the data into several syndromic categories based on the chief complaint of a patient or an admission diagnosis. The fever/ILI category includes visits for undifferentiated fever, chills, myalgias, joint pain, and ILI.

8. The Rapid Risk Factor Surveillance System (RRFSS) is a random-digit-dialed telephone survey of Durham Region residents aged 18 years and older regarding health risk behaviours. The Institute

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for Social Research at York University conducts the survey on behalf of DRHD. DRHD uses the survey during every influenza season to ask residents about their immunization.

9. As per the Ontario Recommendations for the Control of Respiratory Infection Outbreaks in Long-Term Care Homes (2018) and the Influenza Surveillance Protocol for Ontario Hospitals (2018), seasonal immunization coverage rates for staff of LTCHs and public hospitals are reportable to the local Medical Officer of Health.

Public Health Ontario produces a provincial summary of each influenza season in their Public Health Ontario Respiratory Virus Bulletin.

For more information or if you require this information in an accessible format, please contact Durham Health Connection Line at 905-666-6241 or 1-800-841-2729.

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Table 2: Confirmed influenza cases in Durham Region by type and episode week for 2018/19 influenza season compared to previous seasons

Week Beginning

Date

Week Number

Influenza A

Influenza B

Influenza A & B

2018/ 2019 Total

Cases

2017/ 2018 Total

Cases

2016/ 2017 Total

Cases

2015/ 2016 Total

Cases

2014/ 2015 Total

Cases

2013/ 2014 Total Cases

26-Aug 35 1 0 0 1 0 0 0 0 0 2-Sep 36 0 0 0 0 0 0 0 0 0 9-Sep 37 0 1 0 1 1 0 1 0 0 16-Sep 38 0 0 0 0 1 1 2 0 0 23-Sep 39 1 0 0 1 0 1 3 0 0 30-Sep 40 0 0 0 0 0 0 0 0 0 7-Oct 41 0 0 0 0 0 0 0 1 0 14-Oct 42 0 1 0 1 0 2 0 0 1 21-Oct 43 0 0 0 0 0 1 0 0 0 28-Oct 44 0 0 0 0 0 0 1 0 0 4-Nov 45 1 0 0 1 0 0 0 0 0 11-Nov 46 1 0 0 1 1 0 0 0 0 18-Nov 47 1 0 0 1 1 6 0 0 0 25-Nov 48 1 0 0 1 5 5 2 4 4 2-Dec 49 4 0 0 4 4 4 0 14 7 9-Dec 50 9 0 0 9 7 20 0 34 9 16-Dec 51 21 2 1 24 14 21 1 47 19 23-Dec 52 29 0 0 29 17 30 0 58 26 30-Dec 1 41 2 0 43 23 59 1 70 25 6-Jan 2 36 0 0 36 34 48 1 40 27 13-Jan 3 36 3 0 39 34 31 5 28 21 20-Jan 4 35 0 0 35 33 27 12 18 15 27-Jan 5 21 0 0 21 20 31 20 17 7 3-Feb 6 25 0 0 25 45 18 26 14 16 10-Feb 7 14 1 0 15 49 23 44 10 7 17-Feb 8 15 0 0 15 47 14 54 14 7 24-Feb 9 10 0 0 10 23 12 53 5 13 3-Mar 10 12 0 0 12 24 11 59 3 10 10-Mar 11 16 1 0 17 13 7 45 8 9 17-Mar 12 21 0 0 21 18 7 17 4 12 24-Mar 13 14 2 0 16 7 7 29 6 7 31-Mar 14 15 1 0 16 13 4 9 6 9 7-Apr 15 15 3 0 18 8 7 11 4 13 14-Apr 16 5 0 0 5 2 4 6 7 19 21-Apr 17 9 2 0 11 3 0 1 5 13 28-Apr 18 6 2 0 8 2 3 5 1 7 5-May 19 1 8 0 9 2 4 3 0 6 12-May 20 1 2 0 3 0 2 7 3 6 19-May 21 1 0 0 1 1 3 1 0 0 26-May 22 0 2 0 2 2 1 0 0 0 2-Jun 23 0 0 0 0 1 2 0 0 1 9-Jun 24 0 0 0 0 0 1 0 0 0 16-Jun 25 1 0 0 1 0 0 0 0 1 23-Jun 26 0 1 0 1 0 1 0 0 0 30-Jun 27 0 0 0 0 0 0 0 0 0 7-Jul 28 0 0 0 0 0 0 2 0 0 14-Jul 29 0 0 0 0 0 0 0 0 0 21-Jul 30 0 0 0 0 0 0 0 0 0 28-Jul 31 0 0 0 0 0 0 1 0 0 4-Aug 32 0 0 0 0 0 0 0 0 0 11-Aug 33 0 0 0 0 0 0 0 0 0 18-Aug 34 1 0 0 1 0 0 0 0 0 Total -- 420 34 1 455 455 418 422 421 317

Source: Ontario Ministry of Health, integrated Public Health Information System (iPHIS) Database, Extracted by Durham Region Health Department [2019-08-28].

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Figure 1: Confirmed influenza cases in Durham Region by type by influenza season, 2009/10 to 2018/19

Type 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 Total Cases 262 160 111 250 317 421 422 418 455 455 Influenza A 262 133 35 200 188 382 267 382 252 420 Influenza B 0 27 76 50 129 39 155 36 202 34 Influenza A&B 0 0 0 0 0 0 0 0 1 1 % Influenza B 0% 17% 68% 20% 41% 9% 37% 9% 44% 7%

Data Source: Ontario Ministry of Health (MOHLTC), integrated Public Health Information System (iPHIS) Database, Extracted by Durham Region Health Department [2019-08-28].

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Figure 2: Confirmed influenza cases in Durham Region by type; 2018/19 influenza season by week compared to previous seasons

Data Source: Ontario Ministry of Health, integrated Public Health Information System (iPHIS) Database, Extracted by Durham Region Health Department [2019-08-28].

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Figure 3: Age specific incidence rate for confirmed influenza cases, Durham Region and Ontario, 2018/19 influenza season

Rates and Counts 0-4 5-9 10-24 25-39 40-54 55-69 70-79 80+ All Ages Durham Female Rate 248.2 75.3 12.4 30.3 21.6 53.6 132.8 381.6 65.8 Durham Male Rate 212.9 140.9 13.2 12.1 27.0 67.3 174.2 458.2 67.4 Ontario Female Rate 367.0 111.1 25.8 49.8 44.4 81.6 136.3 423.6 95.3 Ontario Male Rate 405.6 134.2 23.5 24.6 41.4 81.6 163.9 420.6 88.0 Durham Female Cases 20 10 13 8 20 43 42 90 246 Durham Male Cases 31 17 9 8 14 30 28 72 209 Durham Total Cases 87 44 17 28 35 77 66 101 455

Data Source: Ontario Ministry of Health, integrated Public Health Information System (iPHIS) Database, Extracted by Durham Region Health Department [2019-08-28]; Ontario MOHLTC, iPHIS database, Public Health Ontario Query: Counts by Age and Gender, Extracted [2019-09-03]; Population Estimates, MOHLTC, IntelliHEALTH ONTARIO.

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Figure 4: Hospitalizations among confirmed influenza cases in Durham Region by influenza season, 2009/10 to 2018/19

Cases 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 Total Cases 262 160 111 250 317 421 422 418 455 455 Hospitalized 77 40 14 68 104 118 101 148 268 267 % Hospitalized 29% 25% 13% 27% 33% 28% 24% 35% 59% 59%

Beginning in the 2017/18 influenza season, only hospital inpatients in an Intensive Care Unit or Critical Care Unit and patients in institutions such as long-term care homes are tested for influenza, as specified in Public Health Ontario’s Respiratory Virus Testing Algorithm. Data Source: Ontario Ministry of Health, integrated Public Health Information System (iPHIS) Database, Extracted by Durham Region Health Department [2019-08-28].

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Figure 5: Hospitalizations among confirmed influenza cases in Durham Region by admission week, 2014/15 to 2018/19

Data Source: Ontario Ministry of Health, integrated Public Health Information System (iPHIS) Database, Extracted by Durham Region Health Department [2019-08-28].

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Figure 6: Number of respiratory outbreaks in institutions by influenza season, 2009/10 to 2018/19

Outbreaks 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 Influenza 1 15 3 19 7 36 6 24 26 13 Other Respiratory 29 13 18 37 23 20 26 39 9 10 Unknown Respiratory 0 7 0 3 4 0 9 6 23 19 Total Respiratory 30 35 21 59 34 56 41 69 58 42 % Influenza 3% 43% 14% 32% 21% 64% 15% 35% 45% 31%

Institutions include Long-Term Care Homes (LTCHs), Hospitals and Retirement Homes. Data Source: Durham Region Health Department, Acute Respiratory Disease Surveillance System (ARDSS).

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Figure 7: Number of respiratory outbreaks in institutions; 2018/19 influenza season by week compared to previous seasons

Institutions include Long-Term Care Homes, Hospitals and Retirement Homes. Onset date may differ from reported date. Data Source: Durham Region Health Department, Acute Respiratory Disease Surveillance System (ARDSS).

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Figure 8: Child absenteeism in child care centres; 2018/19 influenza season by week compared to previous season

Data Source: Sentinel Child Care Centres in Durham Region.

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Figure 9: Number of respiratory outbreaks in child care centres by influenza season, 2009/10 to 2018/19

Year 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 Number of Outbreaks 26 18 6 14 10 12 25 11 24 33

Data Source: Durham Region Health Department, Acute Respiratory Disease Surveillance System (ARDSS).

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Figure 10: Number of respiratory outbreaks in child care centres; 2018/19 influenza season by week compared to previous seasons

Data Source: Durham Region Health Department, Acute Respiratory Disease Surveillance System (ARDSS).

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Figure 11: Absenteeism due to illness in Durham Region schools; 2018/19 influenza season by week compared to average from previous seasons

Data Source: Durham District School Board, Kawartha Pine Ridge District School Board, and Peterborough Victoria Northumberland and Clarington Catholic District School Board.

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Figure 12: Visits to Durham Region emergency departments for fever/ILI; 2018/19 influenza season by week compared to previous seasons

Fever/ILI category includes visits for undifferentiated fever, chills, myalgias, joint pain, and flu like illness (ILI). Data Source: Emergency Department Syndromic Surveillance System, Extracted by Durham Region Health Department [2019-08-28].

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Figure 13: Adults (18+) who had a flu shot during the flu season, Durham Region, 2008/09 to 2018/19

Measure 2008/09 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 Per cent 40% 40% 35% 38% 35% 39% 40% 45% 42% 48% 46% Lower Confidence Interval 36% 37% 31% 34% 32% 35% 36% 41% 38% 44% 42% Upper Confidence Interval 43% 44% 39% 42% 39% 43% 44% 49% 46% 53% 50%

Data Source: Durham Region Health Department, Rapid Risk Factor Surveillance System.

1. 95 per cent Confidence Interval: In this report we included percentages in the form of the point estimate and the 95 per cent confidence interval around the estimate. The true or actual percentage falls within the range of values, 95 out of 100 times. A wide confidence interval reflects a large amount of variability or imprecision. Usually, the larger the sample size, the narrower the confidence intervals. On the graph, the 95 per cent confidence interval is represented by an error bar ( | ) at each point. 2. For the 2009/10 flu season the percentage is for those who had received either the H1N1 or seasonal flu shot or both. 3. We applied household weights when calculating the estimates to compensate for the unequal probability of respondent selection based on the number of adults in the household.

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Figure 14: Adults 18-64 and older adults 65+ who had a flu shot during the flu season, Durham Region, 2008/09 to 2018/19

Measures 2008/09 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 Adults 18-64 33% 35% 29% 31% 28% 32% 30% 34% 31% 37% 30% 18-64 Lower Confidence Interval 29% 31% 25% 27% 24% 27% 26% 30% 26% 32% 26% 18-64 Upper Confidence Interval 36% 39% 33% 36% 32% 36% 34% 39% 35% 42% 35% Older Adults 65+ 74% 69% 78% 72% 68% 67% 67% 73% 68% 70% 68% 65+ Lower Confidence Interval 66% 59% 69% 63% 59% 58% 60% 66% 62% 64% 62% 65+ Upper Confidence Interval 82% 79% 87% 81% 76% 75% 75% 80% 75% 76% 74%

Data Source: Durham Region Health Department, Rapid Risk Factor Surveillance System. 1. 95 per cent Confidence Interval: In this report we included percentages in the form of the point estimate and the 95 per cent confidence interval around the estimate. The true or actual percentage falls within the range of values, 95 out of 100 times. A wide confidence interval reflects a large amount of variability or imprecision. Usually, the larger the sample size, the narrower the confidence intervals. On the graph, the 95 per cent confidence interval is represented by an error bar ( | ) at each point. 2. For the 2009/10 flu season the percentage is for those who had received either the H1N1 or seasonal flu shot or both. 3. We applied household weights when calculating the estimates to compensate for the unequal probability of respondent selection based on the number of adults in the household.

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Figure 15: Median influenza immunization coverage rates among long-term care home and hospital staff; Durham Region and Ontario, 2008/09 to 2018/19 influenza seasons

Residents and Staff 2008/09 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 Durham LTCH Staff 73.3% -- 47.2% 60.4% 57.7% 75.6% 73.9% 68.4% 63.6% 71.0% 73.0% Ontario LTCH Staff 77.0% 44.0% 58.2% 68.0% 74.2% 78.0% 75.7% 72.6% 72.1% 73.0% 72.8% Durham Hospital Staff 39.5% -- 31.3% 30.1% 39.2% 43.1% 45.0% 33.7% 34.3% 47.4% 42.2% Ontario Hospital Staff 51.2% 22.6% 42.2% 49.1% 50.6% 55.4% 60.5% 53.0% 53.1% 54.0% 52.6%

Data Source: Durham Region Health Department, Health Care Worker Immunization Database; Ontario MOHLTC, Ontario Influenza Immunization Database [as of 2018/12/15]; analyzed by Public Health Ontario [2019/03/26]. 1. Health care worker influenza immunization rates in Durham Region were not available for the 2009/10 year due to the 2009 H1N1 pandemic.