3.1 Episodes of influenza, RSV and COVID-19

During the 2024/25 season, 7,584 influenza episodes were reported, peaking in week 51, 2024 with 1,114 episodes. This was earlier and higher than the previous season’s peak of 500 episodes in week 04, 2024 (total: 4,553 episodes) (Figure 3.1).

RSV activity also increased, with 1,959 episodes reported. The peak occurred in week 49, 2024 (218 episodes), compared to 175 episodes in week 46, 2023 (total: 1,541 episodes) (Figure 3.1).

Unlike influenza and RSV, COVID-19 lacks a defined seasonal pattern. During the 2024/25 season, 1,666 episodes were recorded, with a summer 2024 peak in week 26, 2024 (375 episodes). This was a marked decline from the previous season’s 6,785 episodes, which peaked in week 52, 2023 (449 episodes) (Figure 3.1).

Figure 3.1: Weekly number of unique episodes of influenza, RSV and COVID-19 by year and epidemiological week

In the 2024/25 season, influenza episode rates peaked in the 0–4 age group at 229.1 per 100,000 population in week 51, 2024 followed by the 75+ age group in the same week at 159.0 per 100,000. Other age groups showed smaller increases during the same period in the season. These peaks were higher than those observed in the previous season (Figure 3.2).

RSV rates were also highest in the 0–4 age group, peaking at 140.7 per 100,000 in week 49, 2024. This peak was later and higher than the previous season. Other age groups reported lower and later peaks during the same period in the 2024/25 season (Figure 3.2).

For COVID-19, the 75+ age group had the highest episode rates during the summer 2024 peak (weeks 26–28), reaching 86.4 per 100,000. In winter 2023, this group also peaked at 103.6 per 100,000 in week 01, 2024, with lower rates across other age groups in both periods (Figure 3.2).

Figure 3.2: Weekly episode rates of influenza, RSV and COVID-19 per 100,000 population, by age group, by year and epidemiological week

In week 51, 2024, Mid Ulster recorded the highest influenza episode rate (81.7 per 100,000 population), followed by Ards and North Down in the same week (73.2 per 100,000). In contrast, the previous season’s peaks were lower and later, with Antrim and Newtownabbey reporting the highest rate (47.3 per 100,000) in week 04, 2024 (Figure 3.3).

For RSV, the highest rate was in Fermanagh and Omagh in week 48, 2024 (22.2 per 100,000), followed by Belfast in week 50, 2024 (18.0 per 100,000). These peaks were slightly later and higher than the previous season, with Newry, Mourne and Down reporting the highest peak in week 46, 2023 (19.7 per 100,000) (Figure 3.3).

During the summer 2024 COVID-19 peak, Ards and North Down had the highest episode rate in week 25, 2024 (26.2 per 100,000), followed by Armagh City, Banbridge and Craigavon in week 26, 2024 (26.0 per 100,000). In winter 2023, Ards and North Down also had the highest peak with 40.9 per 100,000 in week 51, 2023 (Figure 3.3).

Supplementary tables of unique episodes and weekly episode rates are shown at the end of this report.

Figure 3.3: Weekly episode rates of influenza, RSV and COVID-19 per 100,000 population, by local government district, by year and epidemiological week

3.2 Testing and positivity (%)

During the 2024/25 season, 57,730 influenza tests were conducted, of which 7,892 were positive (13.7%). Of these, 2,530 were influenza A (H1), 382 influenza A (H3), 3,481 influenza A (not subtyped), and 1,499 influenza B. RSV testing resulted in 2,037 positives from 34,562 tests (5.9%), while SARS‑CoV‑2 testing returned 1,894 positives from 57,312 tests (3.3%).

Influenza positivity peaked at 35.2% in week 52, 2024 (954/2,713), earlier and higher than the previous season. RSV positivity peaked at 17.1% in week 47, 2024 (184/1,078), similar to the previous season. SARS‑CoV‑2 positivity peaked at 26.2% in week 26, 2024 (399/1,522) during the summer 2024, and at 22.4% in week 01, 2024 (566/2,529) during the winter 2023 (Figure 3.4).

Figure 3.4: Weekly positivity for influenza, RSV and COVID-19, by year and epidemiological week

Shading represents 95% confidence intervals.

3.3 Influenza subtyping

During the 2024/25 season, 7,584 unique influenza episodes were recorded: 2,297 were influenza A (H1), 354 were influenza A (H3), 3,437 were influenza A (not subtyped), and 1,496 were influenza B (Figure 3.5). In contrast, the previous season saw 4,553 episodes, comprising 459 influenza A (H1), 1,571 influenza A (H3), 2,325 influenza A (not subtyped), and 198 influenza B. The 2024/25 season was dominated by influenza A (H1), with minimal influenza A (H3) activity and a slower decline due to a late season rise in influenza B cases.

A supplementary table of influenza subtyping is shown at the end of this report.

Figure 3.5: Weekly number of unique episodes of influenza, by subtype and by year and epidemiological week

3.4 Sentinel surveillance

Sentinel surveillance plays a role in monitoring and understanding the spread and impact of respiratory viruses in the community. It involves a systematic and targeted approach to collect data from a geographical representative subset of GP practices (~18% population representative) to provide information about virus activity across Northern Ireland.

During the 2024/25 season, 443 of 1,166 samples submitted to the Regional Virus Laboratory (RVL) tested positive for influenza (38.0% positivity) (Table 1). Influenza A (H1) was the predominant strain, accounting for 254 positives, followed by 27 influenza A (H3), 44 influenza A (not subtyped), and 118 influenza B. For RSV, 67 of 1,161 samples were positive (5.8%), and for COVID-19, 23 of 1,159 samples tested positive for SARS-CoV-2 (2.0%) (Table 1).

The highest number of sentinel tests for influenza, RSV, and COVID-19 (106 samples) were submitted in week 51 of 2024. Age specific data are presented in (Figure 3.6), (Figure 3.7), (Figure 3.8) and Table 2.

A supplementary table of testing and positivity is shown at the end of this report.

Figure 3.6: Weekly sentinel influenza cases, by age group, by epidemiological week

Figure 3.7: Weekly sentinel RSV cases, by age group, by epidemiological week

Figure 3.8: Weekly sentinel COVID-19 cases, by age group, by epidemiological week

3.5 Non-sentinel surveillance

Non-sentinel surveillance is the monitoring of respiratory viruses from virology data collected from settings such as hospitals and GPs (excluding the sentinel GPs). This provides information about virus activity across Northern Ireland.

During the 2024/25 season, 7,449 of 56,564 samples tested across Northern Ireland were positive for influenza (13.2% positivity) (Table 1). Influenza A (H1) was the predominant strain, with 2,276 positives, followed by 355 influenza A (H3), 3,437 influenza A (not subtyped), and 1,381 influenza B. For RSV, 1,970 of 33,401 samples were positive (5.9%), and for COVID-19, 1,871 of 56,153 samples tested positive for SARS-CoV-2 (3.3%) (Table 3).

The highest number of non-sentinel tests for influenza (3,200 samples), RSV (1,687 samples), and COVID-19 (3,140 samples) were submitted in week 51, 2024. Age specific data are shown in (Figure 3.9), (Figure 3.10), (Figure 3.11) and Table 4.

A supplementary table of testing and positivity is shown at the end of this report.

Figure 3.9: Weekly non-sentinel influenza cases, by age group, by epidemiological week

Figure 3.10: Weekly non-sentinel RSV cases, by age group, by epidemiological week

Figure 3.11: Weekly non-sentinel COVID-19 cases, by age group, by epidemiological week

3.6 SARS-CoV-2 variants

Unlike influenza and RSV, COVID-19 does not follow a distinct seasonal pattern, with activity occurring at various times throughout the year.

Peaks in COVID-19 activity were observed in winter 2023 and summer 2024, but no clear peak was seen during winter 2024. Among the subset of SARS-CoV-2 positive PCR samples that were sequenced, different prominent variants were identified:

• During winter 2023 (December 23 - February 24), JN.1 accounted for 65.8% of all samples sequenced with a lineage assigned (368/559) (Figure 3.12).

• During summer 2024 (June 24 - August 24), KP.3 accounted for 70.8% of all samples sequenced with a lineage assigned (322/455) (Figure 3.12).

• During winter 2024 (December 24 - February 25), XEC accounted for 59.8% of all samples sequenced with a lineage assigned (64/107) (Figure 3.12).

Due to small numbers of samples sequenced, the level of confidence in precision of the estimate is low, and the percentages of each variant may change as further results become available.

Parent lineages displayed are subject to change based on lineages under monitoring by the UKHSA horizon scanning team.

A supplementary table of sequenced samples for variants in Northern Ireland during the 2024/25 influenza season is shown at the end of this report.

Figure 3.12: Total number of sequenced variants of COVID-19 by Pangolin lineage, by year and epidemiological week

Recombinant refers to any recombinant lineage, starting “X”, that does not fall under the parent lineage of a defined variant.

4.1 Consultation rates for influenza/influenza-like-illness (‘flu/ILI’)

The GP flu/ILI consultation rate exceeded the pre-epidemic threshold for low activity (10.1 per 100,000 population) in week 49, 2024 and remained above baseline for 13 consecutive weeks, returning to baseline in week 10, 2025. The peak consultation rate occurred in week 51, 2024, reaching 39.2 per 100,000. This peak was earlier than in the previous season but aligned with the 2022/23 season (Figure 4.1).

By age group, the highest consultation rate was observed in the 0–4 age group in week 51, 2024 (73.4 per 100,000), followed by the 75+ age group in week 01, 2025 (57.9 per 100,000) (Figure 4.2).

Regionally, the highest rates were recorded in the Western Trust in week 01, 2025 (54.7 per 100,000), followed by the South Eastern Trust (48.6 per 100,000) in the same week (Figure 4.3).

Supplementary tables of GP consultation rates are shown at the end of this report.

Figure 4.1: Northern Ireland GP consultation rates for ‘flu/ILI’ 2021/22 – 2024/25

The baseline MEM threshold for Northern Ireland is <10.1 per 100,000 population for 2024-25. Low activity is 10.1 to <20.5, moderate activity 20.5 to <47.4, high activity 47.4 to <68.5 and very high activity is >68.5 per 100,000 population.

Figure 4.2: Northern Ireland GP consultation rates for ‘flu/ILI’ 2021/22 – 2024/25, by age group

Figure 4.3: Northern Ireland GP consultation rates for ‘flu/ILI’ 2021/22 – 2024/25, by Health and Social Care Trust

4.2 Consultation rates for acute respiratory infection (ARI)

The highest ARI consultation rate during the 2024/25 season was recorded in week 51, 2024, at 233.5 per 100,000 population. This peak occurred around the same time as in previous seasons, closely aligning with the previous season but remaining lower than the peak observed in 2022/23 (Figure 4.4).

By age group, consultation rates were consistently highest among the 0–4 age group, peaking in week 48, 2024, at 1,107.6 per 100,000 (Figure 4.5).

Regionally, the highest ARI consultation rates were reported in the Western Trust in week 51, 2024 (271.8 per 100,000), followed by the South Eastern Trust (252.7 per 100,000) in the same week (Figure 4.6).

Supplementary tables of GP consultation rates are shown at the end of this report.

Figure 4.4: Northern Ireland GP consultation rates for ARI 2021/22 – 2024/25

Figure 4.5: Northern Ireland GP consultation rates for ARI 2021/22 – 2024/25, by age group

Figure 4.6: Northern Ireland GP consultation rates for ARI 2021/22 – 2024/25, by Health and Social Care Trust

5.1 Influenza, RSV and COVID-19 care homes outbreaks

During the 2024/25 season, fewer respiratory outbreaks in care homes were reported to the PHA Health Protection acute response duty room compared to the previous season. This decline is largely attributed to reduced COVID-19 circulation and the predominance of influenza A (H1), with minimal influenza A (H3) activity. Seasons dominated by influenza A (H3) typically see more care home outbreaks and higher hospital admissions among older adults. In total, 83 respiratory outbreaks were reported (Figure 5.1).

Of these, there was one influenza A (H1), 43 influenza A (not subtyped), one influenza B, eight RSV, and 30 COVID-19 outbreaks in care home settings. The highest number of outbreaks occurred in week 01, 2025, with 14 confirmed outbreaks: 10 influenza A (not subtyped), two RSV, and two COVID-19 (Figure 5.1).

A supplementary table of confirmed care home outbreaks are shown at the end of this report.

Figure 5.1: Weekly number of confirmed influenza, RSV and COVID-19 outbreaks, by year and epidemiological week

6.1 Admissions and occupancy

During the 2024/25 season, total community-acquired emergency respiratory admissions remained similar to the previous influenza season, with 4,533 admissions recorded. However, this season saw a higher peak, driven by influenza A admissions (2,480) and a notable rise in influenza B admissions later in the season (441). RSV admissions (1,079) were comparable to the previous season, while COVID-19 admissions (533) declined substantially (Figure 6.1).

Admissions began rising in week 47, 2024, peaking in week 51, 2024 with 525 admissions, 77% of which were due to influenza A. From week 6, 2025, influenza B overtook influenza A as the leading cause of admissions (Figure 6.1). RSV admissions peaked in week 49, 2024 (129), aligning with the previous season’s timing. COVID-19 admissions peaked earlier, in week 27, 2024 (120), during summer 2024 (Figure 6.1).

Age specific admission rates showed the 75+ age group had the highest influenza rates in week 52, 2024 (97.7 per 100,000 population), followed by the 0–4 age group in week 51, 2024 (54.9 per 100,000). These peaks were higher to what was reported in the previous season across age groups. RSV admission rates were highest in the 0–4 age group, peaking in week 49, 2024 (93.8 per 100,000). This peak were similar to what was reported in the previous season. COVID-19 admission rates peaked in the 75+ age group in week 26, 2024 (40.9 per 100,000) (Figure 6.2).

Inpatient occupancy mirrored these trends. Influenza A inpatients peaked at 341 on 31 December 2024, earlier and higher than the previous season’s peak. Influenza B contributed to a slower decline in admissions later in the 2024/25 season. RSV inpatients peaked at 64 on 04 December, 2024, slightly later than the previous season. COVID-19 inpatients peaked at 129 on 22 July, 2024 before declining again and remained low thereafter (Figure 6.3).

Supplementary tables of community-acquired emergency hospital admissions are shown at the end of this report.

Figure 6.1: Weekly number of community-acquired emergency influenza, RSV and COVID-19 hospital admissions, by year and epidemiological week

Figure 6.2: Weekly rates of community-acquired emergency influenza, RSV and COVID-19 hospital admissions per 100,000 population, by age group, by year and epidemiological week

Figure 6.3: Influenza, RSV and COVID-19 community acquired emergency inpatients, by day

7.1 Deaths related to influenza and/or pneumonia

NISRA death statistics report on deaths where influenza and/or pneumonia was mentioned anywhere on the death certificate. As a result, the counts will reflect deaths where influenza and/or pneumonia has contributed to a death but was not necessarily the underlying cause of the death.

During the 2024/25 season, there were 2,216 deaths involving influenza and/or pneumonia out of 11,689 total registered deaths (19.0%). This proportion is similar to the previous season, which saw 2,293 such deaths out of 11,925 registered (19.2%). The number and proportion of influenza and/or pneumonia-related deaths increased over the course of the season, peaking in week 52, 2024, when 28.5% of all registered deaths involved influenza and/or pneumonia (Figure 7.1).

A supplementary table of deaths are shown at the end of this report.

Figure 7.1: Weekly deaths and percentage of registered deaths related to influenza and/or pneumonia, to most recent registration week

7.2 Deaths related to COVID-19

NISRA death statistics report on deaths where COVID-19 was mentioned anywhere on the death certificate. As a result, the counts will reflect deaths where COVID-19 has contributed to a death but was not necessarily the underlying cause of the death.

During the 2024/25 season, 97 COVID-19-related deaths were reported out of 11,689 total registered deaths (0.8%). This is a decrease from the previous season, which recorded 278 COVID-19 deaths out of 11,925 (2.3%). The proportion of deaths involving COVID-19 declined following a summer 2024 peak in week 30, 2024 (4.5%) and remained between 0–3% throughout the 2024/25 season (Figure 7.2).

A supplementary table of deaths are shown at the end of this report.

Figure 7.2: Weekly deaths and percentage of registered deaths related to COVID-19, to most recent registration week

7.3 Excess Mortality

NISRA use the UK-wide methodology to report on excess deaths as advised by the Office for National Statistics (ONS).

EuroMOMO is a European mortality monitoring activity, aiming to detect and measure excess deaths related to seasonal influenza, pandemics and other public health threats. Reports on excess deaths across Europe and the United Kingdom are published weekly.

8.1 Seasonal Influenza vaccination 2024/25

The Seasonal Influenza Vaccination Programme 2024/25 commenced in Northern Ireland on 07 October 2024 and ended on 31 March 2025. A total of 593,318 influenza vaccinations were administered during the 2024/25 seasonal influenza vaccination programme. Uptake of influenza vaccination was highest in care home residents (80%) and individuals aged 65 years and over (73.7%). Vaccine uptake in eligible children was highest in primary school children (64.9%). The final vaccine uptake for the 2024/25 seasonal programme is available in the Seasonal Influenza Vaccination Surveillance in Northern Ireland 2024/25 report.