Severe acute respiratory infections (SARI) surveillance report, Ireland

Weekly Report on Severe Acute Respiratory Infections (SARI), Ireland

Week 43 2025 (week ending 26/10/2025)

Report prepared on 30/10/2025

1 About this report

As of week 40 2025, four sentinel hospital sites are participating in Ireland’s severe acute respiratory infections (SARI) surveillance programme. The most recent addition is Children’s Health Ireland at Crumlin (CHI-C), commencing on 29^th September 2025. St Vincent’s University Hospital (SVUH) was the first site to join, commencing SARI surveillance on 5^th July 2021. This was followed by St James’s Hospital (SJH) and University Hospital Limerick (UHL, paediatric cases only) both commenced on 30^th September 2024 (Week 40 2024).

The data presented in this report were extracted from the HPSC SARI surveillance database on 30/10/2025. These figures are provisional and subject to ongoing review, validation and updates. Consequently, they may differ from previously published data as refinements are made to improve accuracy.

Three of the SARI sentinel hospital sites (75%) reported data for the current week (W43 2025). Variations in the number of sentinel sites reporting each week, should be considered when comparing incidence rates and case numbers from previous weeks.

2 Key message

In week 43 2025, SARI activity remained stable and at low levels in Ireland; 61 SARI cases were reported from three of the four sentinel hospital sites, compared to 59 cases reported from the same three sentinel sites in week 42 2025.

SARS CoV-2 test positivity increased, while influenza and RSV test positivity remained at low levels in week 43 (both at 3.8%). SARS CoV-2 test positivity increased from 2.7% in week 42 to 11.3% in week 43, due in particular to an increase in test positivity at one of the adult sentinel sites (27.8%).

3 Summary

SARI case numbers and incidence:

• 61 SARI cases were admitted to three SARI sentinel sites in week 43 2025, compared to 75 cases from four sites in week 42 2025.

• SARI cases <15 years: 24 cases from one sentinel site in week 43 2025, compared to 31 cases from two sentinel sites in week 42 2025.

• SARI cases ≥15 years: 37 cases from two sentinel sites in week 43 2025, compared to 44 cases from two sentinel sites in week 42 2025.

The incidence rates per 1,000 hospital admissions* were as follows:

• All SARI cases: 72.3 in week 43 2025, compared to 81.6 in week 42 2025 (11.4% decrease).

• SARI cases <15 years: 158.9 in week 43 2025, compared to 144.2 in week 42 2025 (10.2% increase).

• SARI cases ≥15 years: 53.4 in week 43 2025, compared to 62.5 in week 42 2025 (14.6% decrease).

*See technical notes section for further information on SARI hospital admissions data

Age profile (week 43 2025): 42.6% (n=26) cases were aged ≥65 years and 29.5% (n=18) cases aged <5 years:

• All SARI cases: median age 60 years; IQR: 3-75 years.

• SARI cases <15 years: median age 2 years, IQR: 1-4 years.

• SARI cases ≥15 years: median age 72 years, IQR: 63-83 years.

Virus test positivity among SARI cases (week 43 2025): Among those tested (86.9%, n=53):

• 11.3% (n=6) tested positive for SARS-CoV-2, compared to 2.7% (n=2) in week 42 2025. Among SARI cases aged <15 years and ≥15 years, 0.0% (n=0) and 19.4% (n=6) tested positive for SARS CoV-2 in week 43 2025, respectively. The increase in SARS-CoV-2 test positivity can be attributed mainly to an increase in one of the adult sentinel hospital sites who reported a positivity of 27.8% (n=5).

• 3.8% (n=2) tested positive for influenza (1 AH3; 1 B), compared to 5.4% (n=4) in week 42 2025. Among SARI cases aged <15 years and ≥15 years, 9.1% (n=2) and 0.0% (n=0) tested positive for influenza in week 43 2025, respectively.

• 3.8% (n=2) tested positive for RSV, compared to 2.7% (n=2) in week 42 2025. Among SARI cases aged <15 years and ≥15 years, 9.1% (n=2) and 0.0% (n=0) tested positive for RSV in week 43 2025, respectively.

Genomic surveillance (week 21 2025 to week 43 2025): Among SARI SARS-CoV-2 positive specimens sequenced (n=41), XFG was the dominant variant at 63.4% (n=26), followed by LP.8.1 at 12.2% (n=5).

Influenza and RSV typing/subtyping (week 21 2025 to week 43 2025):

For cases admitted since week 21 2025, influenza A was the predominant virus circulating amongst influenza positive SARI cases, consisting of A(H3) at 35.3% (n=6), followed by A(H1)pdm09 at 23.5% (n=4) and 35.3% (n=6) awaiting subtyping.

Underlying medical conditions (week 43 2025): Overall 85.2% (n=52) of SARI cases reported at least one underlying medical condition. This included 62.5% (n=15) of cases among those aged <15 years and 100.0% (n=37) among those aged ≥15 years.

Severe outcomes (week 21 2025 to week 43 2025)

• 3.4% (n=34) of SARI cases were admitted to ICU, this included 2.7% (n=9) among those aged <15 years and 3.8% (n=25) among those aged ≥15 years of age. Overall, the median length of stay was 4 days, IQR 2-9 days. Among the SARI cases admitted to ICU, 2.9% (n=1) were positive for SARS-CoV-2, 0.0% (n=0) for influenza and 2.9% (n=1) for RSV.

• 4.0% (n=43) of SARI cases died in hospital. The median age was 78 years, IQR 73.5-86.5 years, 93.0% (n=40) were ≥65 years of age

Vaccination status (week 21 2025 to week 42 2025) These data are reported with a one-week time lag

• Amongst SARI cases positive for SARS CoV-2, aged ≥6 months and with known vaccination status (n=87), 92% (n=80) had NOT received a COVID-19 vaccine dose in the six months prior to the reported episode of illness.

4 SARI case numbers and incidence rates

4.1 SARI cases by site

Figure 4.1: Number of SARI cases by sentinel hospital site and by week of admission week 21 2025 to week 43 2025 (n=1056)

Note: CHI-C included from week 40 2025.

4.2 Incidence admissions

Figure 4.2: SARI age-specific incidence rates per 1,000 hospital admissions by week of admission week 21 2025 to week 43 2025

*SARI cases are recruited from emergency department admissions only in SVUH, SJH and UHL. In CHI-C cases are recruited from emergency department and non-emergency department routes (e.g. transfer from other hospitals, direct admission to speciality wards), excluding day cases and elective admissions.

Note: CHI-C included from week 40 2025.

4.3 SARI cases by age group

Figure 4.3: Number of SARI cases by age group and week of admission week 21 2025 to week 43 2025

Note: CHI-C included from week 40 2025.

4.4 Incidence (All seasons)

Figure 4.4: SARI incidence rates per 1,000 hospital admissions by week of admission between week 40 2021 and week 43 2025

NOTE: In seasons 2021/2022, 2022/2023 & 2023/2024 one hospital site (SVUH) participated in SARI surveillance. In the 2024/2025 season three hospital sites (SVUH, SJH & UHL) participated, and four sites (SVUH, SJH, UHL & CHI-C) participated in season 2025/2026.

5 Demographics

Table 1: Number and proportion of SARI cases by sex and age, for the current week (week 43 2025), last four weeks (week 40 2025 to week 43 2025) and week 21 2025 to week 43 2025

		Current week	Last four weeks	Total
		W43 2025	W40 2025-W43 2025	W21 2025-W43 2025
Characteristic	Category	N = 61	N = 277	N = 1,065
Gender	Female	28 (45.9)	135 (48.7)	517 (48.5)
	Male	33 (54.1)	142 (51.3)	548 (51.5)
Age <15 years (in years)	Median (IQR)	2 (1 - 4)	1 (0 - 4)	2 (0 - 5)
	Range	0 - 14	0 - 14	0 - 14
Age ≥15 years (in years)	Median (IQR)	72 (63 - 83)	71 (61 - 82)	73 (62 - 81)
	Range	35 - 95	24 - 100	16 - 100
Age groups (years)	<1	6 (9.8)	37 (13.4)	87 (8.2)
	1-4	12 (19.7)	60 (21.7)	164 (15.4)
	5-14	6 (9.8)	26 (9.4)	88 (8.3)
	15-34	0 (0.0)	6 (2.2)	27 (2.5)
	35-64	11 (18.0)	40 (14.4)	182 (17.1)
	65-79	12 (19.7)	62 (22.4)	301 (28.3)
	80+	14 (23.0)	46 (16.6)	216 (20.3)

Note: CHI-C included from week 40 2025.

6 PCR testing for SARS-CoV-2, Influenza and RSV

SARI cases are tested on-site in each hospital by PCR for SARS-CoV-2, influenza and RSV on admission.

Table 2: Number and proportion of SARI cases PCR positive for SARS-CoV-2, influenza, and RSV for the current week, last four weeks (week 40 2025 to week 43 2025) and week 21 2025 to week 43 2025

	Current week		Last four weeks		Total
	W43 2025		W40 2025-W43 2025		W21 2025-W43 2025
	<15y N = 221	≥15y N = 311	<15y N = 1181	≥15y N = 1481	<15y N = 3281	≥15y N = 6601
SARS-CoV-2	0 (0.0)	6 (19.4)	6 (5.1)	12 (8.1)	38 (11.6)	79 (12.0)
Influenza	2 (9.1)	0 (0.0)	5 (4.2)	3 (2.0)	7 (2.1)	10 (1.5)
RSV	2 (9.1)	0 (0.0)	7 (5.9)	0 (0.0)	9 (2.7)	1 (0.2)
1n (%)

Note: CHI-C included from week 40 2025. Between week 21 2025 to week 43 2025, 1 SARI case was coinfected with more than one of the three viruses under surveillance.

A further breakdown of SARI test positivity by hospital site is available in the Appendix.

6.1 Number PCR positive

Figure 6.1: Number of SARI cases PCR positive for SARS-CoV-2, influenza and RSV by week of hospital admission week 21 2025 to week 43 2025

NOTE: CHI-C included from week 40 2025

6.2 Percentage PCR positive

Figure 6.2: Percentage of SARI cases PCR positive for SARS-CoV-2, influenza, RSV and overall positivity by week of hospital admission week 21 2025 to week 43 2025

Note: CHI-C included from week 40 2025.

6.3 Percentage PCR positive by age group

Figure 6.3: Weekly positivity rate of SARI cases PCR positive for SARS-CoV-2, influenza and RSV by age group and by week of hospital admission week 21 2025 to week 43 2025

Note: CHI-C included from week 40 2025 and Y-axis scale may differ for each age group

7 SARS-CoV-2 genomic analysis

Note: There is typically a lag time of at least 3 weeks between a case being admitted, positive samples selected for sequencing and sequencing being completed and reported.

For further information on circulating variants in Ireland, see Respiratory virus notification data hub - Health Protection Surveillance Centre (hpsc.ie) and Integrated Respiratory Virus Bulletin.

Table 3: Number and proportion of SARS CoV-2 positive SARI cases sequenced and reported by Pango lineage and variant week 21 2025 to week 43 2025

Variant	n	%	Pango Lineage	n	%
XFG	26	63.4	XFG	9	22.0
			XFG.2	2	4.9
			XFG.22.1	2	4.9
			XFG.3	9	22.0
			XFG.3.1	1	2.4
			XFG.3.10	1	2.4
			XFG.3.8	1	2.4
			XFG.5	1	2.4
LP.8.1	5	12.2	LP.8.1.1	1	2.4
			LP.8.1.9	1	2.4
			PF.1	1	2.4
			PF.2	1	2.4
			PR.2	1	2.4
NB.1.8.1	5	12.2	NB.1.8.1	3	7.3
			PQ.1	1	2.4
			PQ.4	1	2.4
BA.2.86	3	7.3	NL.22.1	1	2.4
			PY.1	1	2.4
			XFC	1	2.4
XEC	2	4.9	XEC.4	1	2.4
			XFN	1	2.4
Total	41	100.0	-	41	99.5

NOTE: CHI-C included from week 40 2025

7.1 SARS-CoV-2 variants by week

Figure 7.1: Number of SARS CoV-2 positive SARI cases, by variant and week of hospital admission, week 21 2025 to week 43 2025 (n=117)

*Includes sub-lineage JN.1, excludes lineage KP.3

**Sample either not suitable for sequencing, or result is pending

NOTE: CHI-C included from week 40 2025

7.2 SARS-CoV-2 variants season to date

Figure 7.2: Proportion of SARS CoV-2 positive SARI cases sequenced, week 21 2025 to week 43 2025 (n=41)

*Includes sub-lineage JN.1, excludes lineage KP.3

8 Influenza typing/subtyping

8.1 Influenza typing/subtyping by week

Figure 8.1: Number of influenza positive SARI cases by type/subtype and by week of admission, week 21 2025 to week 43 2025 (n=17)

Note: CHI-C included from week 40 2025.

8.2 Influenza typing/subtyping (all age groups)

Figure 8.2: Proportion of influenza positive SARI cases by type/subtype, week 21 2025 to week 43 2025 (n=17)

Note: CHI-C included from week 40 2025.

8.3 Influenza typing/subtyping (<15 years and ≥15 years)

Figure 8.3: Proportion of influenza positive SARI cases by type/subtype among those aged <15 years (n=7) and ≥15 years (n=10) week 21 2025 to week 43 2025

Note: CHI-C included from week 40 2025.

9 RSV typing

9.1 RSV typing by week

Figure 9.1: Number of RSV positive SARI cases by RSV type and by week of admission, week 21 2025 to week 43 2025 (n=10)

Note: CHI-C included from week 40 2025.

10 Symptoms

Table 4: Number and proportion of SARI cases’ clinical symptoms, either at or prior to hospital admission, for the last four weeks (week 40 2025 to week 43 2025), and week 21 2025 to week 43 2025

	Last four weeks		Total
	W40 2025-W43 2025		W21 2025-W43 2025
Clinical symptoms	<15y N = 123	≥15y N = 154	<15y N = 339	≥15y N = 726
Cough	99 (80.5)	131 (85.1)	239 (70.5)	611 (84.2)
Shortness of breath	25 (20.3)	141 (91.6)	88 (26.0)	635 (87.5)
Fever	82 (66.7)	75 (48.7)	254 (74.9)	382 (52.6)
General deterioration	72 (58.5)	60 (39.0)	72 (21.2)	295 (40.6)
Malaise	88 (71.5)	26 (16.9)	152 (44.8)	120 (16.5)
Nausea/Vomiting	39 (31.7)	18 (11.7)	106 (31.3)	91 (12.5)
Sore throat	37 (30.1)	7 (4.5)	123 (36.3)	47 (6.5)
Increased work of breathing	80 (65.0)	0 (0.0)	104 (30.7)	0 (0.0)
Coryza	76 (61.8)	0 (0.0)	83 (24.5)	0 (0.0)
Diarrhoea	18 (14.6)	9 (5.8)	33 (9.7)	41 (5.6)
Acute confusion	0 (0.0)	10 (6.5)	0 (0.0)	72 (9.9)
Muscular pain	1 (0.8)	10 (6.5)	1 (0.3)	59 (8.1)
Headache	2 (1.6)	5 (3.2)	11 (3.2)	40 (5.5)
Sepsis	2 (1.6)	0 (0.0)	4 (1.2)	8 (1.1)
Ageusia/Dysgeusia/Anosmia	0 (0.0)	1 (0.6)	1 (0.3)	1 (0.1)
Apnoea	0 (0.0)	0 (0.0)	1 (0.3)	0 (0.0)

Note: CHI-C included from week 40 2025. Collection of data on additional symptoms i.e. increased work of breathing and coryza was implemented from week 39 2025

11 Underlying medical conditions and risk factors

SARI cases may be reported with one or more underlying medical conditions. Weekly proportions can be based on small numbers and vary from week to week, caution is therefore advised when interpreting changes in weekly proportions (Table 5).

Table 5: Number and proportion of SARI cases with underlying medical conditions reported on hospital admission (among those who reported having underlying medical conditions), for the last four weeks (week 40 2025 to week 43 2025), week 21 2025 to week 43 2025

	Last four weeks		Total
	W40 2025-W43 2025		W21 2025-W43 2025
Condition	<15y N = 123	≥15y N = 154	<15y N = 339	≥15y N = 726
No underlying medical conditions	63 (51.2)	13 (8.4)	201 (59.3)	44 (6.1)
Lung disease	2 (1.6)	76 (49.4)	6 (1.8)	333 (45.9)
Heart disease	11 (8.9)	56 (36.4)	18 (5.3)	300 (41.3)
Hypertension	0 (0.0)	61 (39.6)	0 (0.0)	280 (38.6)
Cancer	1 (0.8)	31 (20.1)	1 (0.3)	183 (25.2)
Neurological disease	6 (4.9)	27 (17.5)	21 (6.2)	141 (19.4)
Rheumatological disease	1 (0.8)	31 (20.1)	1 (0.3)	150 (20.7)
Asthma	13 (10.6)	23 (14.9)	34 (10.0)	105 (14.5)
Diabetes	0 (0.0)	25 (16.2)	0 (0.0)	115 (15.8)
Immunocompromised	3 (2.4)	13 (8.4)	4 (1.2)	92 (12.7)
Kidney disease	1 (0.8)	13 (8.4)	2 (0.6)	67 (9.2)
Dementia	0 (0.0)	11 (7.1)	0 (0.0)	65 (9.0)
Liver disease	0 (0.0)	13 (8.4)	0 (0.0)	40 (5.5)
Obesity	0 (0.0)	5 (3.2)	2 (0.6)	29 (4.0)
Intellectual disability	2 (1.6)	4 (2.6)	18 (5.3)	9 (1.2)
Down syndrome	4 (3.3)	1 (0.6)	7 (2.1)	3 (0.4)
Tuberculosis	0 (0.0)	0 (0.0)	0 (0.0)	3 (0.4)
Asplenia	0 (0.0)	0 (0.0)	2 (0.6)	0 (0.0)
Cystic fibrosis	0 (0.0)	0 (0.0)	0 (0.0)	1 (0.1)
Long COVID	0 (0.0)	0 (0.0)	0 (0.0)	1 (0.1)

Note: CHI-C included from week 40 2025.

12 Clinical course and outcome

12.1 Complications

Information on the clinical course during hospitalisation is only available after patient discharge, and there may be a delay between discharge and data collection, due to the manual data collection methods required. Furthermore, data collection is ongoing for those not yet discharged from hospital.

SARI cases could be reported with one or more complications; among those for whom discharge information is available the most common complication reported was pneumonia (Table 6).

Table 6: Number and proportion of SARI cases and complications among discharged SARI cases, for the last four weeks (week 40 2025 to week 43 2025), and week 21 2025 to week 43 2025

	Last four weeks		Total
	W40 2025-W43 2025		W21 2025-W43 2025
Complication	<15y N = 91	≥15y N = 68	<15y N = 305	≥15y N = 628
No complications	59 (64.8)	6 (8.8)	185 (60.7)	104 (16.6)
Pneumonia	13 (14.3)	55 (80.9)	61 (20.0)	420 (66.9)
Acute kidney injury	0 (0.0)	2 (2.9)	0 (0.0)	48 (7.6)
Bronchiolitis	5 (5.5)	0 (0.0)	43 (14.1)	1 (0.2)
Heart failure	0 (0.0)	4 (5.9)	0 (0.0)	42 (6.7)
Sepsis	0 (0.0)	0 (0.0)	1 (0.3)	23 (3.7)
ARDS	3 (3.3)	0 (0.0)	22 (7.2)	1 (0.2)
Secondary bacterial infections	1 (1.1)	1 (1.5)	3 (1.0)	18 (2.9)
Multi organ failure	0 (0.0)	0 (0.0)	0 (0.0)	5 (0.8)
Other complications	7 (7.7)	6 (8.8)	10 (3.3)	90 (14.3)

Note: CHI-C included from week 40 2025. Collection of data on additional complications i.e. acute atrial fibrillation, acute viral myositis and respiratory complications was implemented from week 39 2025

The following complications have been removed from the table, as there are no cases reporting these conditions in the above time-periods: Myocarditis, Encephalitis, PIMS*, Acute atrial fibrillation, Acute viral myositis, Respiratory complications

*Paediatric inflammatory multisystem syndrome

12.2 Respiratory support

Among SARI cases who have been discharged, the highest level of respiratory support received during hospitalisation is described in Table 7.

Table 7: Number and proportion of SARI cases by highest level of respiratory support received, among discharged SARI cases, for the last four weeks (week 40 2025 to week 43 2025), and week 21 2025 to week 43 2025

	Last four weeks		Total
	W40 2025-W43 2025		W21 2025-W43 2025
Respiratory support	<15y N = 911	≥15y N = 681	<15y N = 3051	≥15y N = 6281
No respiratory support given	51 (57%)	21 (34%)	202 (66%)	223 (37%)
Low-flow oxygen therapy	27 (30%)	33 (53%)	68 (22%)	266 (45%)
Non-invasive ventilation	12 (13%)	8 (13%)	34 (11%)	98 (16%)
Invasive ventilation	0 (0%)	0 (0%)	0 (0%)	8 (1.3%)
1n (%)

Note: CHI-C included from week 40 2025.

12.3 Severe outcomes

SARI cases are considered to have severe outcomes if they were admitted to ICU and/or died during their hospital stay.

Table 8: Number and proportion of SARI cases with severe outcomes, for the last four weeks (week 40 2025 to week 43 2025), and week 21 2025 to week 43 2025

	Last four weeks	Total
	W40 2025-W43 2025	W21 2025-W43 2025
	N = 277	N = 1,065
Hospital length of stay (days)
Median (IQR)	3 (2 - 5)	4 (2 - 7)
Range	1 - 23	1 - 109
Admitted to ICU, n (%)	10 (4.6%)	34 (3.4%)
ICU length of stay (days)
Median (IQR)	-	5 (3 - 10)
Range	-	1 - 67
Died in hospital, n (%)	2 (0.7%)	43 (4.0%)

Note: CHI-C included from week 40 2025. Paediatric cases from UHL may be reported as admitted to ICU, if transferred to an ICU in another paediatric hospital. However, these cases are excluded from the calculation of length of stay in ICU.

13 Vaccination status

Vaccination data are available approximately one week after cases are notified to HPSC, therefore the vaccination status for the current week’s SARI cases have been excluded from the below analysis.

13.1 COVID-19 vaccination status

During week 21 2025 to week 42 2025 among SARI cases PCR positive for SARS-CoV-2, aged ≥6 months and with known COVID-19 vaccination status (n=87), 92% (n=80) had NOT received a vaccine dose in the six months prior to the reported episode of illness (Table 9).

Table 9: Characteristics of SARI cases positive for SARS-CoV-2 during week 21 2025 to week 42 2025 by time since last COVID-19 vaccine dose

		W21 2025-W42 2025
Characteristic	Category	<180 days N = 7	≥180 days N = 80
Gender	Female	3 (7.3%)	38 (92.7%)
	Male	4 (8.7%)	42 (91.3%)
Age (years)	Median (IQR)	85 (74 - 89)	73 (48 - 81)
	Range	49 - 96	0 - 93
Age groups (years)	0-14	0 (0.0%)	18 (100.0%)
	15-59	1 (12.5%)	7 (87.5%)
	60-69	1 (12.5%)	7 (87.5%)
	70-79	1 (4.3%)	22 (95.7%)
	80+	4 (13.3%)	26 (86.7%)
Underlying medical conditions	Yes	7 (9.5%)	67 (90.5%)
	No	0 (0.0%)	13 (100.0%)
	Unknown	0 (0.0%)	0 (0.0%)
Patient residence	Residential care facility	3 (27.3%)	8 (72.7%)
	Private residence/home	4 (5.3%)	72 (94.7%)
	Other/unknown residence	0 (0.0%)	0 (0.0%)

Note: CHI-C included from week 40 2025. Due to small numbers of cases reported as not vaccinated, this group has been included in the ≥180 days group.

Excluded from analysis:

• SARS-CoV-2 positive SARI cases with unknown vaccination status, 5 (4.5%) are excluded.

• SARS-CoV-2 positive SARI cases aged <6 months, 19 (17.1%) are excluded.

13.2 Influenza vaccination status

Vaccination status of influenza positive SARI cases will be reported when >10 cases are admitted during the current 2025/2026 season.

14 Links to other national respiratory virus reports

Respiratory viruses

• Integrated Respiratory Virus Bulletin

• Respiratory Virus Notification Hub

COVID-19

• National Wastewater Surveillance Programme

15 Appendix

Table A1: Number of SARI cases, number tested and positivity by hospital site for the current week (week 43 2025), previous week (week 42 2025) and week 21 2025 to week 43 2025

	Cases	SARS CoV-2 tested	SARS CoV-2 positive	Influenza & RSV tested	Influenza positive	RSV positive
Site	n	n	n (%)	n	n (%)	n (%)
W43 2025	61	53	6 (11.3)	53	2 (3.8)	2 (3.8)
SVUH	19	18	5 (27.8)	18	0 (0.0)	0 (0.0)
SJH	18	13	1 (7.7)	13	0 (0.0)	0 (0.0)
UHL	-	-	-	-	-	-
CHI-C	24	22	0 (0.0)	22	2 (9.1)	2 (9.1)
W42 2025	75	74	2 (2.7)	74	4 (5.4)	2 (2.7)
SVUH	24	24	1 (4.2)	24	3 (12.5)	0 (0.0)
SJH	20	20	0 (0.0)	20	0 (0.0)	0 (0.0)
UHL	16	16	0 (0.0)	16	0 (0.0)	1 (6.3)
CHI-C	15	14	1 (7.1)	14	1 (7.1)	1 (7.1)
W21 2025-W43 2025	1065	988	117 (11.8)	988	17 (1.7)	10 (1.0)
SVUH	339	331	48 (14.5)	331	8 (2.4)	0 (0.0)
SJH	387	329	31 (9.4)	329	2 (0.6)	1 (0.3)
UHL	247	240	34 (14.2)	240	2 (0.8)	3 (1.3)
CHI-C	92	88	4 (4.5)	88	5 (5.7)	6 (6.8)

16 Technical Notes

16.1 SARI Surveillance objectives

Severe acute respiratory infection (SARI) is of major relevance to public health worldwide. Surveillance of SARI is essential to monitor the (co-) circulation of respiratory pathogens and to assess disease severity. Data collected as part of SARI surveillance can provide important early warning information in the context of respiratory disease outbreaks and pandemics. SARI data can also be used as a platform to measure vaccine and antiviral effectiveness and impact. The objectives of SARI surveillance are:

• To describe the number and incidence of SARI cases by aetiology, time, place and person

• To describe and monitor trends, intensity of activity and severity of SARI infections

• To identify groups at risk of severe disease

• To detect unusual and unexpected events

• To assess the SARI burden of disease in the participating hospital

• To assess and monitor vaccine effectiveness

16.2 Sentinel hospital SARI surveillance sites

SARI surveillance has been implemented in four sentinel hospital sites in Ireland.

1. St.Vincent’s University Hospital (SVUH), tertiary care adult hospital commenced 5^th of July 2021 (week 27 2021)

2. St James’s Hospital (SJH), tertiary care adult hospital commenced 30^th September 2024 (week 40 2024)

3. University Hospital Limerick (UHL), tertiary care hospital (for SARI surveillance purposes reports on paediatric cases only) commenced 30^th September 2024 (week 40 2024)

4. Children’s Health Ireland at Crumlin (CHI-C) provides quarternary and tertiary healthcare services for children nationally and secondary care for the local catchment area, commenced 29^th September 2025 (week 40 2025)

SVUH and SJH report on SARI cases aged 15 years and older while UHL and CHI-C report on SARI cases aged under 15 years.

16.3 Case definition

SARI cases are identified from new admissions, based on clinical symptoms. Patients that develop SARI during their admission are not included.

Clinical SARI case:

The European Centre for Disease Prevention and Control (ECDC) clinical SARI case definition was used for SARI surveillance in Ireland since week 34 2021. The case definition was adapted in Ireland for infants aged <6 months to include increased work of breathing and apnoea as relevant symptoms. This revised definition was applied to cases admitted from week 40 2025.

SARI case definition: A person hospitalised for at least 24 hours with acute respiratory infection and symptom onset within 14 days prior to hospital admission, with at least one of the following symptoms:

• cough

• fever

• shortness of breath

• sudden onset of anosmia, ageusia or dysgeusia

• increased work of breathing*

• apnoea*

*for infants aged <6 months

A SARI case refers to an individual patient episode of care.

16.4 Denominator data

Weekly denominator data on all-cause hospital admissions are provided by the sentinel hospital sites. SVUH, SJH and UHL provide data on admissions via the emergency department only; CHI-C provide data on admissions via the emergency department and non-emergency department routes (e.g. transfer from other hospitals, direct admission to speciality wards), excluding day cases and elective admissions.

16.5 Laboratory testing

SARS-CoV-2, influenza, and RSV PCR testing is carried out on admission.

SARI samples that are positive for SARS-CoV-2 and have a cycle threshold (Ct) value <25 are referred for whole genome sequencing (WGS). The molecular laboratories in SVUH, SJH and UHL are spoke WGS testing sites as part of the national SARS-CoV-2 WGS surveillance programme, for further information please see Whole Genome Sequencing Programme - Health Protection Surveillance Centre (hpsc.ie). SARI WGS testing is performed on-site at SVUH, SJH, UHL and CHI-C.

Samples that are PCR positive for influenza are sent to the National Virus Reference Laboratory (NVRL) for influenza typing/subtyping/genetic and antigenic characterisation.

Samples that are PCR positive for RSV are sent to the National Virus Reference Laboratory (NVRL) for RSV typing.

16.6 Data collection and reporting

St Vincent’s University Hospital: Clinical data are collected and managed using REDCap electronic data capture tools hosted at University College Dublin. Laboratory data are extracted from APEX, the laboratory information management system (LIMS), using IBM Cognos software hosted at SVUH.

St. James’s Hospital: Clinical data are collected and managed on a specifically adapted electronic form within the patient’s electronic patient record (EPR). Laboratory data are extracted from Telepath LIMS.

University Hospital Limerick: Clinical data are collected manually on the hard copy of the UHL SARI Case Report Form (CRF) and then recorded in the electronic SARI questionnaire on ICNET. Details of laboratory results are obtained from ICNET and are also recorded in the electronic SARI questionnaire on ICNET.

Children’s Health Ireland at Crumlin: Clinical data are collected and managed using REDCap electronic data capture tools hosted by the Children’s Research Centre. Laboratory data are extracted from Winpath LIMS.

Case-based data are reported by SVUH, SJH, UHL & CHI-C to the HSE Health Protection Surveillance Centre (HPSC) on a weekly basis. Data are also reported by HPSC to ECDC via The European Surveillance System (TESSy) on weekly basis as part of the European SARI surveillance programme.

COVID-19 and influenza vaccination data are obtained from the National COVID-19 Vaccination Management System (COVAX) and linked to SARI cases by the HSE-Integrated Information Service (IIS), where data are available.

16.7 Reference dates

Respiratory virus seasons and dates

The respiratory virus surveillance season runs from week 40 (early October) to week 20 (end of May). During this time, seasonal respiratory viruses usually circulate at higher levels, compared to the summer period (weeks 21 to 39). The seasonal comparisons used in this report refer to the respiratory virus surveillance season.

04/10/2021 (Week 40 2021) - start of the 2021/2022 season

03/10/2022 (Week 40 2022) - start of the 2022/2023 season

02/10/2023 (Week 40 2023) - start of the 2023/2024 season

30/09/2024 (Week 40 2024) - start of the 2024/2025 season

29/09/2025 (Week 40 2025) - start of the 2025/2026 season

SARI surveillance

05/07/2021 (Week 27 2021) – commenced of SARI surveillance at first sentinel hospital site (SVUH)

30/09/2024 (Week 40 2024) - commenced SARI surveillance at the second and third sentinel hospital sites (SJH & UHL)

29/09/2025 (Week 40 2025) - commenced SARI surveillance at the fourth sentinel hospital site (CHI-C)

Vaccination campaign dates

27/09/2021 (Week 39 2021) – first COVID-19 booster vaccination campaign commenced

22/04/2022 (Week 16 2022) – second COVID-19 booster vaccination campaign commenced

03/10/2022 (Week 40 2022) – Autumn 2022 COVID-19 booster vaccination campaign commenced

28/04/2023 (Week 17 2023) – Spring 2023 COVID-19 booster vaccination campaign commenced

02/10/2023 (Week 40 2023) – Autumn 2023 COVID-19 booster vaccination campaign commenced

22/04/2024 (Week 17 2024) – Spring 2024 COVID-19 booster vaccination campaign commenced

30/09/2024 (Week 40 2024) – Autumn 2024 influenza & COVID-19 booster vaccination campaign commenced

03/04/2025 (Week 13 2025) – Spring 2025 COVID-19 booster vaccination campaign commenced

02/10/2025 (Week 40 2025) – Autumn 2025 influenza & COVID-19 booster vaccination campaign commenced

Winter respiratory virus seasons

04/10/2021 (Week 40 2021) - start of the 2021/2022 season

03/10/2022 (Week 40 2022) - start of the 2022/2023 season

02/10/2023 (Week 40 2023) - start of the 2023/2024 season

30/09/2024 (Week 40 2024) - start of the 2024/2025 season

29/09/2025 (Week 40 2025) - start of the 2025/2026 season

Week number refers to the week of hospital admission. Weeks are from Monday to Sunday, as per the international ISO week.

The international ISO week runs from Monday to Sunday and is used as per ECDC/WHO/International reporting protocol.

16.8 Vaccination status definitions

For the purposes of SARI surveillance, vaccination status of cases is as follows:

Vaccinated COVID case: A confirmed case of COVID-19 who received any dose of a COVID-19 vaccine, ≥14 days before onset of symptoms.

Unvaccinated COVID-19 case: A confirmed case of COVID-19 who did not receive any dose of a COVID-19 vaccine i.e. was never vaccinated.

Time since vaccination: For a vaccinated COVID-19 case, this is the time between the date of last dose vaccination and the date of symptom onset and categorised as <180 days or ≥180 days since vaccination.

Vaccinated influenza case: A confirmed case of influenza will be considered as vaccinated against influenza if they received one dose of the influenza vaccine as part of the current season’s influenza vaccination campaign ≥14 days before onset of symptoms.

Unvaccinated influenza case: A confirmed case of influenza will be considered as unvaccinated if they did not receive an influenza vaccine as part of the current season’s influenza vaccination campaign or if they were vaccinated after onset of symptoms.

Vaccine status unknown: The SARI patient is reported on the SARI hospital clinical questionnaire as vaccinated, however there is no identifiable linked record of COVID-19 vaccination and/or influenza vaccination on the National Immunisation system (COVAX). Vaccination status is reported as unknown, until verified on the National Immunisation system.

17 Acknowledgements

Sincere thanks are extended to all those who participate in SARI surveillance, including those in St. Vincent’s University Hospital, St James’s Hospital, University Hospital Limerick, Children’s Health Ireland at Crumlin and the National Virus Reference Laboratory. Thanks to members of the HSE Integrated Information Services (IIS) for work on the SARI-COVAX data linkages.

This report was produced by the SARI surveillance team at HPSC, using R studio software.