FluWatch report: October 28, 2018 to November 3, 2018 (Week 44)

Figure 1 - Text description

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	No Activity
N.L.	Labrador-Grenfell	Sporadic
N.L.	Central	No Activity
N.L.	Western	No Activity
P.E.I.	Prince Edward Island	No Activity
N.S.	Zone 1 - Western	No Activity
N.S.	Zone 2 - Northern	No Activity
N.S.	Zone 3 - Eastern	Sporadic
N.S.	Zone 4 - Central	No Activity
N.B.	Region 1	No Activity
N.B.	Region 2	No Activity
N.B.	Region 3	No Activity
N.B.	Region 4	No Activity
N.B.	Region 5	No Activity
N.B.	Region 6	No Activity
N.B.	Region 7	No Activity
Que.	Nord-est	Sporadic
Que.	Québec et Chaudieres-Appalaches	Sporadic
Que.	Centre-du-Québec	Sporadic
Que.	Montréal et Laval	Sporadic
Que.	Ouest-du-Québec	Sporadic
Que.	Montérégie	Sporadic
Ont.	Central East	Sporadic
Ont.	Central West	Sporadic
Ont.	Eastern	Localized
Ont.	North East	No Activity
Ont.	North West	Sporadic
Ont.	South West	Sporadic
Ont.	Toronto	Localized
Man.	Northern Regional	Sporadic
Man.	Prairie Mountain	No Activity
Man.	Interlake-Eastern	No Activity
Man.	Winnipeg	Sporadic
Man.	Southern Health	No Activity
Sask.	North	Sporadic
Sask.	Central	Sporadic
Sask.	South	Sporadic
Alta.	North Zone	Sporadic
Alta.	Edmonton	Sporadic
Alta.	Central Zone	Sporadic
Alta.	Calgary	Localized
Alta.	South Zone	Sporadic
B.C.	Interior	Sporadic
B.C.	Fraser	Sporadic
B.C.	Vancouver Coastal	Sporadic
B.C.	Vancouver Island	Sporadic
B.C.	Northern	No Activity
Y.T.	Yukon	No Activity
N.W.T.	North	No Activity
N.W.T.	South	No Activity
Nvt.	Qikiqtaaluk	No Activity
Nvt.	Kivalliq	No Activity
Nvt.	Kitimeot	No Activity

Laboratory Confirmed Influenza Detections

In week 44, the following results were reported from sentinel laboratories across Canada (Figure 2):

• The percentage of tests positive for influenza remained above the seasonal threshold at 7.7% of tests positive.
• The percentage of tests positive for influenza A is higher for this time of year compared to the same period during the previous eight seasons. Laboratory detections of influenza have entered seasonal levels three weeks earlier than the median over the previous eight seasons.
• In week 44, 359 laboratory detections of influenza were reported, of which 98% were influenza A.

To date this season 883 laboratory-confirmed influenza detections have been reported (Figure 3):

• 94% have been influenza A
• Among the 531 influenza A viruses subtyped, 73% have been A(H1N1)pdm09

To date this season, detailed information on age and type/subtype has been received for 815 laboratory-confirmed influenza cases (Table 1):

• Adults 20-44 years of age represent the largest proportion of cases (27%), followed by adults 45-64 years of age (20%) and children 5-19 years of age (19%).

For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.

Figure 2 - Text description

Surveillance Week	A(Unsubtyped)	A(H3)	A(H1)pdm09	Influenza B
35	3	2	7	0
36	4	7	4	0
37	3	2	3	1
38	6	3	2	3
39	11	5	1	3
40	16	7	29	3
41	27	6	21	3
42	40	19	55	2
43	83	23	128	4
44	137	13	203	6

Figure 3 - Text description

Reporting provincesTable Figure 3 - Footnote 1	Week (October 28, 2018 to November 3, 2018)					Cumulative (August 26, 2018 to November 3, 2018)
	Influenza A				B	Influenza A				B	A & B Total
	A Total	A (H1N1)pdm09	A (H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total	A Total	A (H1N1)pdm09	A (H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total
BC	18	8	5	5	0	83	27	34	22	2	85
AB	228	146	4	78	1	489	303	24	162	10	499
SK	13	0	13	0	6	60	0	60	0	31	91
MB	14	11	2	1	0	41	37	2	2	0	41
ON	16	5	2	9	2	71	20	21	30	7	78
QC	32	0	0	32	3	73	0	0	73	6	79
NB	1	1	0	0	0	4	1	0	3	0	4
NS	1	0	0	1	0	3	0	0	3	0	3
PEI	0	0	0	0	0	1	1	0	0	0	1
NL	1	1	0	0	0	2	1	0	1	0	2
YT	0	0	0	0	0	0	0	0	0	0	0
N.W.T	0	0	0	0	0	0	0	0	0	0	0
NU	0	0	0	0	0	0	0	0	0	0	0
Canada	324	172	26	126	12	827	390	141	296	56	883
PercentageTable Figure 3 - Footnote 2	96%	53%	8%	39%	4%	94%	47%	17%	36%	6%	100%
Table Figure 3 - Footnote 1 Specimens from NWT, YT, and Nvt are sent to reference laboratories in other provinces. Return to Table Figure 3 - Footnote 1 Table Figure 3 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections. Return to Table Figure 3 - Footnote 2 Table Figure 3 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available. Return to first Table Figure 3 - Footnote 3 Discrepancies in values in Figures 2 and 3 may be attributable to differing data sources. Cumulative data includes updates to previous weeks.

Table 1 - Cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, weeks 2018-35 to 2018-44

Age groups (years)	Cumulative (August 26, 2018 to November 3, 2018)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	132	82	3	47	<5	>132	-
5-19	151	88	2	61	<5	>151	-
20-44	213	113	9	91	5	218	27%
45-64	160	89	16	55	<5	>160	-
65+	138	67	34	37	6	144	18%
Total	794	439	64	291	>11	>794	100%
Table 1 - Note 1 UnS: unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available; Return to Table 1 - Note 1

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 44, 1.0% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 4). The percentage of visits for ILI is within expected levels.

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2013-14 to 2017-18

Figure 4 - Text description

Report week	2018-19	Average	Min	Max
35	0.6%	0.6%	0.4%	0.9%
36	0.7%	0.8%	0.5%	1.0%
37	0.6%	0.9%	0.7%	1.1%
38	0.5%	1.0%	0.7%	1.4%
39	1.8%	1.1%	0.8%	1.5%
40	0.6%	1.6%	0.9%	3.4%
41	1.1%	1.6%	1.1%	2.1%
42	1.2%	1.4%	0.8%	1.8%
43	1.1%	1.4%	0.7%	1.8%
44	1.0%	1.4%	1.1%	1.6%

Participatory Syndromic Surveillance

In week 44, 2,151 participants reported to FluWatchers, of which 27 (1.3%) reported symptoms of cough and fever (Figure 5).

Among the 27 participants who reported fever and cough:

• 15% consulted a healthcare professional
• 70% reported days missed from work or school, resulting in a combined total of 50 missed days of work or school.

Figure 5 - Text description

Surveillance week	% cough and fever
40	2.6%
41	2.5%
42	1.7%
43	1.5%
44	1.3%

Influenza Outbreak Surveillance

In week 44, one new laboratory-confirmed influenza outbreak associated with influenza A(H1N1)pdm09 was reported in another type of facility (i.e. not in the category of school/daycare, hospital, long-term care facility or remote/isolated community).

To date this season, 9 influenza outbreaks have been reported (Figure 6): 

• Five outbreaks were in long-term care facilities, one was in a school, and three were in other settings.
• Among the outbreaks for which the influenza A subtype was available, three were associated with influenza A(H1N1)pdm09, two with A(H3N2) and one was associated with both A(H1N1)pdm09 and A(H3N2).

One new ILI outbreak in a long-term care facility was reported in week 44.

To date this season, 21 ILI outbreaks have been reported; 19 occurred in LTC facilities, one in a school, and one in a hospital.

Figure 6 - Text description

Surveillance Week	Acute Care Facilities	Long Term Care Facilities	Other	Schools and Daycares	Remote and/or Isolated Communities
35	0	0	0	0	0
36	0	0	0	0	0
37	0	0	0	0	0
38	0	1	0	0	0
39	0	0	0	0	0
40	0	2	0	1	0
41	0	0	0	0	0
42	0	1	1	0	0
43	0	1	1	0	0
44	0	0	1	0	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 44, 49 influenza-associated hospitalizations were reported, which is an increase compared to the previous week.

To date this season, 129 influenza-assocaited hospitalizations have been reported by participating provinces and territories^Footnote 1.

Hospitalizations (Table 2):

• 98% (127) were associated with influenza A
• Adults 65 years of age and older represent the largest proportion of hospitalizations (34%),  followed by adults 45-64 years of age (23%).

Intensive Care Unit (ICU) cases and deaths:

• To date this season 16 ICU admissions and <5 deaths have been reported.

Table 2 – Cumulative number of hospitalizations by age-group reported by participating provinces and territories^{Footnote 1}, Canada, weeks 2018-35 to 2018-44

Age Groups	Cumulative (August 26, 2018 to November 3, 2018)
(years)	Total	%
0-4	16	12%
5-19	18	14%
20-44	21	16%
45-64	30	23%
65+	44	34%
Total	129	100%

Pediatric Influenza Hospitalizations and Deaths

To date this season, 37 pediatric hospitalizations have been reported by the Immunization Monitoring Program Active (IMPACT) network.

• All 37 cases have been associated with influenza A.
• Among the 29 for which the influenza subtype was available, 28 were associated with A(H1N1)pdm09.
• 32 of the 37 cases were between 6 months and 9 years of age.

To date this season, 7 ICU admissions, and no deaths have been reported.

Figure 7 - Text description

Surveillance week	2018-19	Average	Min	Max
35	0	0	0	1
36	0	0	0	1
37	0	0	0	2
38	0	1	0	2
39	0	1	0	3
40	1	0	0	2
41	1	1	0	3
42	6	1	0	4
43	10	2	0	7
44	19	2	1	6

Adult Influenza Hospitalizations and Deaths

Surveillance of laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations by the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) network began on November 1^st for the 2018-19 season.

To date this season, fewer than 5 hospitalizations have been reported, all were associated with influenza A.

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 21 influenza viruses (4 A(H3N2) and 17 A(H1N1)) that were received from Canadian laboratories.

Genetic Characterization of Influenza A (H3N2):

Three influenza A(H3N2) viruses did not grow to sufficient hemagglutination titer for antigenic characterization by hemagglutination inhibition (HI) assay. Therefore, NML has performed genetic characterization to determine the genetic group identity of this virus.
Sequence analysis of the HA gene of the viruses showed that:

• One virus belonged to genetic group 3C.2a.
• Two viruses belonged to subclade 3C.2a1.

A/Singapore/INFIMH-16-0019/2016-like virus belongs to genetic group 3C.2a1 and is the influenza A(H3N2)  component of the 2018-19 Northern Hemisphere influenza vaccine.

Antigenic Characterization:

Influenza A(H3N2):

• One influenza A(H3N2) virus was antigenically characterized as A/Singapore/INFIMH-16-0019/2016-like by HI testing using antiserum raised against egg-propagated A/Singapore/INFIMH-16-0019/2016.
• A/Singapore/INFIMH-16-0019/2016-like virus is the influenza A(H3N2) component of the 2018-19 Northern Hemisphere influenza vaccine.
• The influenza A (H3N2) virus characterized belonged to genetic group 3C.2a1.

Influenza A(H1N1):

• Seventeen A(H1N1) viruses characterized were antigenically similar to A/Michigan/45/2015, which is the influenza A(H1N1) component of the 2018-19 Northern Hemisphere influenza vaccine.

Antiviral Resistance

Antiviral Resistance – Amantadine:

Twenty influenza A (4 A(H3N2) and 16 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

• The four A(H3N2) viruses tested were resistant to amantadine.
• The 16 A(H1N1) viruses tested were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

Nineteen influenza viruses (4 A(H3N2) and 15 A(H1N1)) were tested for resistance to oseltamivir and it was found that:

• The four A(H3N2) viruses tested were sensitive to oseltamivir
• The 15 A(H1N1) viruses tested were sensitive to oseltamivir

Antiviral Resistance – Zanamivir:

Nineteen influenza viruses (4 A(H3N2) and 15 H1N1) were tested for resistance to zanamivir and it was found that:

• The four A(H3N2) viruses were sensitive to zanamivir.
• The 15 A(H1N1) viruses were sensitive to zanamivir.