FluWatch report: November 4, 2018 to November 10, 2018 (Week 45)

Figure 1 - Text description

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	No Activity
N.L.	Labrador-Grenfell	No Activity
N.L.	Central	No Activity
N.L.	Western	No Activity
P.E.I.	Prince Edward Island	Sporadic
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	Sporadic
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	No Activity
Que.	Montréal et Laval	Sporadic
Que.	Ouest-du-Québec	Sporadic
Que.	Montérégie	Sporadic
Ont.	Central East	Sporadic
Ont.	Central West	Sporadic
Ont.	Eastern	Sporadic
Ont.	North East	No Activity
Ont.	North West	No Activity
Ont.	South West	Sporadic
Ont.	Toronto	Localized
Man.	Northern Regional	No Activity
Man.	Prairie Mountain	Sporadic
Man.	Interlake-Eastern	Sporadic
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	Sporadic
Nvt.	Qikiqtaaluk	No Activity
Nvt.	Kivalliq	No Activity
Nvt.	Kitimeot	Sporadic

Laboratory Confirmed Influenza Detections

In week 45, the following results were reported from sentinel laboratories across Canada (Figure 2):

• The percentage of tests positive for influenza continued to increase to 9.6% 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 45, 509 laboratory detections of influenza were reported, of which 97% were influenza A.

To date this season 1,523 laboratory-confirmed influenza detections have been reported (Figure 3):

• 97% have been influenza A
• Among the 922 influenza A viruses subtyped, 80% have been A(H1N1)pdm09

To date this season, detailed information on age and type/subtype has been received for 1,457 laboratory-confirmed influenza cases (Table 1):

• Adults 20-44 years of age represent the largest proportion of cases (25%), followed by adults >65 years of age (20%).

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	170	13	213	6
45	201	17	276	15

Figure 3 - Text description

Reporting provincesTable Figure 3 - Footnote 1	Week (October 28, 2018 to November 10, 2018)					Cumulative (August 26, 2018 to November 10, 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	9	7	2	0	0	92	34	36	22	2	94
AB	371	235	4	132	1	877	547	28	302	11	888
SK	32	11	0	21	0	140	78	3	59	0	140
MB	16	4	0	12	0	57	41	2	14	0	57
ON	27	10	11	6	12	183	31	117	35	19	202
QC	47	0	0	47	1	120	0	0	120	7	127
NB	0	0	0	0	0	4	1	0	3	0	4
NS	2	0	0	2	0	5	0	0	5	0	5
PEI	1	1	0	0	0	2	2	0	0	0	2
NL	0	0	0	0	1	2	1	0	1	1	3
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	1	1	0	0	0	1	1	0	0	0	1
Canada	506	269	17	220	15	1483	736	186	561	40	1523
PercentageTable Figure 3 - Footnote 2	97%	53%	3%	43%	3%	97%	50%	13%	38%	3%	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 2018-45

Age groups (years)	Cumulative (August 26, 2018 to November 10, 2018)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	>241	150	<5	91	<5	248	-
5-19	>266	159	<5	107	5	>271	-
20-44	365	193	12	160	8	373	-
45-64	263	137	25	101	6	269	-
65+	282	106	116	60	10	292	-
Total	>1264	745	>153	519	>29	>1293	-
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 45, 2.0% 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	1,0%	1,4%	0,7%	1,8%
44	0,9%	1,4%	1,1%	1,6%
45	2,0%	1,5%	1,2%	1,8%

Participatory Syndromic Surveillance

In week 45, 2,069 participants reported to FluWatchers, of which 35 (1.7%) reported symptoms of cough and fever (Figure 5).

Among the 35 participants who reported fever and cough:

• 20% consulted a healthcare professional
• 63% reported days missed from work or school, resulting in a combined total of 55 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%
45	1.7%

Influenza Outbreak Surveillance

In week 45, five new laboratory-confirmed influenza outbreaks were reported in a long-term care facility (LTCF) (1), schools (3), and another type of facility (1).

To date this season, 18 influenza outbreaks have been reported (Figure 6): 

• Eight outbreaks were in LTCF, six were in schools, and four were in other settings.
• 15 of the 18 outbreaks were associated with influenza A.
• Among the outbreaks for which the influenza A subtype was available:
  • Six were associated with influenza A(H1N1)pdm09, reported from schools and other settings;
  • Four were associated with A(H3N2), reported from LTCF and other settings;
  • Two were associated with both A(H1N1)pdm09 and A(H3N2), reported from LTCF.
• Compared to previous seasons, a greater proportion of outbreaks have been reported in settings other than LTCF, suggesting an increased burden of disease in younger age-groups.

One new ILI outbreak in a LTCF was reported in week 45.

To date this season, 22 ILI outbreaks have been reported; 20 occurred in LTCF, 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	2	0
45	0	1	1	3	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 45, 65 influenza-associated hospitalizations were reported, which is an increase compared to the previous week.

To date this season, 218 influenza-assocaited hospitalizations have been reported by participating provinces and territories^Footnote 1.

Hospitalizations (Table 2):

• 99% (216) were associated with influenza A
• Adults 65 years of age and older represent the largest proportion of hospitalizations (29%),  followed by adults 45-64 years of age (24%).

Intensive Care Unit (ICU) cases and deaths:

• To date this season 28 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 2018-45

Age Groups	Cumulative (August 26, 2018 to November 10, 2018)
(years)	Total	%
0-4	37	17%
5-19	32	15%
20-44	34	16%
45-64	52	24%
65+	63	29%
Total	218	100%

Pediatric Influenza Hospitalizations and Deaths

TIn week 45, 31 pediatric (≤16 years of age) hospitalizations with influenza have been reported by the Immunization Monitoring Program Active (IMPACT) network. Pediatric hospitalizations reported by IMPACT are at levels not normally seen until late December (4-6 weeks earlier than in recent seasons).

To date this season, 68 pediatric hospitalizations have been reported:

• All 68 cases have been associated with influenza A.
• Among the 51 for which the influenza subtype was available, 50 were associated with A(H1N1)pdm09.
• 56 of the 68 cases (82%) 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	11	1	0	3
44	19	3	1	6
45	31	3	2	4

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, six hospitalizations have been reported, of which five were associated with influenza A and one with influenza B.

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 43 influenza viruses (4 A(H3N2), 38 A(H1N1) and one B) 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 these viruses.

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):

• 38 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.

Influenza B:

Influenza B viruses can be divided into two antigenically distinct lineages represented by B/Yamagata/16/88 and B/Victoria/2/87 viruses. The recommended influenza B components  for the 2018-19 Northern Hemisphere influenza vaccine are  B/Colorado/06/2017 (Victoria lineage) and B/Phuket/3073/2013 (Yamagata lineage).

• One influenza B viruses was characterized as B/Phuket/3073/2013-like, which belongs to the Yamagata lineage and is included as an influenza B component of the 2018-19 Northern Hemisphere quadrivalent influenza vaccine.

Antiviral Resistance

Antiviral Resistance – Amantadine:

23 influenza A (4 A(H3N2) and 19 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 19 A(H1N1) viruses tested were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

49 influenza viruses (9 A(H3N2), 39 A(H1N1) and 1 B) were tested for resistance to oseltamivir and it was found that:

• The 9 A(H3N2) viruses tested were sensitive to oseltamivir
• The 39 A(H1N1) viruses tested were sensitive to oseltamivir
• The B virus was sensitive to oseltamivir

Antiviral Resistance – Zanamivir:

48 influenza viruses (9 A(H3N2), 38 H1N1 and 1 B) were tested for resistance to zanamivir and it was found that:

• The 9 A(H3N2) viruses were sensitive to zanamivir.
• The 38 A(H1N1) viruses were sensitive to zanamivir.
• The B virus was sensitive to zanamivir.