2.1 Episodes of influenza, RSV and COVID-19

The number of new influenza episodes decreased in week 12, with 113 unique episodes identified. There were 122 episodes reported in week 11. The number of new RSV episodes decreased in week 12, with five unique episodes identified. There were eight episodes reported in week 11 (Figure 2.1).

Influenza and RSV episode rates by age groups are shown in (Figure 2.2). The highest influenza episode rate in week 12 was in the 0-4 age group (22.1 per 100,000 population). The highest RSV episode rate was in the 0-4 age group (1.8 per 100,000 population).

Influenza rates across local government districts (LGD) are shown in (Figure 2.3). Mid Ulster had the highest influenza rate in week 12 (8.0 per 100,000 population). The highest RSV rate was in Lisburn and Castlereagh (1.3 per 100,000 population).

The number of new COVID-19 episodes decreased in week 12, with 18 unique episodes identified compared with 24 in week 11 (Figure 2.1).

COVID-19 episode rates by age groups are shown in (Figure 2.2). The highest COVID-19 episode rate in week 12 was in the 75+ age group (5.3 per 100,000 population).

COVID-19 episode rates across LGD are shown in (Figure 2.3). Ards and North Down had the highest COVID-19 episode rate in week 12 (2.4 per 100,000 population).

Supplementary tables of key figures are shown at the end of this bulletin.

Figure 2.1: Weekly number of unique episodes of influenza, RSV and COVID-19 by epidemiological week

Figure 2.2: Weekly episode rates of influenza, RSV and COVID-19 per 100,000 population, by age group, by epidemiological week

Figure 2.3: Weekly episode rates of influenza, RSV and COVID-19 per 100,000 population, by local government district, by epidemiological week

2.2 Testing and positivity (%)

In week 12 there were 1,579 total influenza tests, 116 of which were positive (7.4% positivity). This is a slight decrease from week 11 (7.9% positivity) (Figure 2.4).

There were 920 total RSV tests, five of which were positive (0.5% positivity). This is a slight decrease compared with week 11 (0.9% positivity) (Figure 2.4).

There were 1,574 COVID-19 tests, 19 of which were positive (1.2% positivity). This is lower than week 11 (1.7% positivity) (Figure 2.4).

Supplementary tables of key figures are shown at the end of this bulletin.

Figure 2.4: Weekly positivity for influenza, RSV and COVID-19, by epidemiological week

2.3 Influenza subtyping

Of the 113 new influenza episodes identified in week 12, two were typed as Flu A (H1), 15 were Flu A (H3), 16 were Flu A (not subtyped) and 80 were Flu B (Figure 2.5).

Figure 2.5: Weekly number of unique episodes of influenza, by subtype and epidemiological week

2.4 Sentinel surveillance

Sentinel surveillance plays a role in monitoring and understanding the spread and impact of respiratory viruses like influenza and COVID-19 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 NI.

In week 12, five samples were positive for influenza from 21 samples submitted for testing (23.8% positivity) to the Regional Virus Laboratory (RVL). One was for Flu A (H3) and four were Flu B. No samples were positive for RSV from 21 samples submitted for testing. There was one positive COVID-19 sample from 21 samples (4.8% positivity) submitted for testing. (Table 1).

Total sentinel cases of influenza, RSV and COVID-19 by age group for the previous year are shown in (Figure 2.6), (Figure 2.7) and (Figure 2.8), and cumulatively for the 2024/25 influenza season in Table 2.

Supplementary tables of key figures are shown at the end of this bulletin.

Figure 2.6: Weekly sentinel influenza cases, by age group, by epidemiological week

Figure 2.7: Weekly sentinel RSV cases, by age group, by epidemiological week

Figure 2.8: Weekly sentinel COVID-19 cases, by age group, by epidemiological week

2.5 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 NI.

In week 12, 111 samples were positive for influenza from 1,558 samples submitted for testing to laboratories across NI (7.1% positivity). Five were typed as Flu A (H1), 14 were Flu A (H3), 16 were Flu A (not subtyped), and 76 were Flu B. Five samples were positive for RSV from 899 samples submitted for testing (0.6% positivity). 18 samples were positive for COVID-19 from 1,553 samples submitted for testing (1.2% positivity) (Table 3).

Total non-sentinel cases of influenza, RSV and COVID-19 by age group for the previous year are shown in (Figure 2.6), (Figure 2.7) and (Figure 2.11), and cumulatively for the 2024/25 influenza season in Table 4.

Supplementary tables of key figures are shown at the end of this bulletin.

Figure 2.9: Weekly non-sentinel influenza cases, by age group, by epidemiological week

Figure 2.10: Weekly non-sentinel RSV cases, by age group, by epidemiological week

Figure 2.11: Weekly non-sentinel COVID-19 cases, by age group, by epidemiological week

2.6 SARS-CoV-2 variants

XEC is a recombinant lineage of KS.1.1 and KP.3.3 (both of which are JN.1 sub-lineages). The KP.3 and other KP lineages are descended from JN.1 sub-lineages, and they are now reported separately from JN.1 to illustrate the evolving genomic epidemiology. For the week commencing 23 December 2024, XEC accounted for 50.0% of all sequenced samples, KP.3 for 38.9%, and for JN.1 and KP both 5.6%, respectively. 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. A more detailed COVID-19 Genomics Bulletin containing a further breakdown of sub-lineages is published weekly. Technical information is published by UKSHA on some specific KP variants online.

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

Figure 2.12: Total number of sequenced variants of COVID-19 by Pangolin lineage, by epidemiological week

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

3.1 Consultation rates for influenza/influenza-like-illness (‘flu/FLI’)

The general practice (GP) flu/FLI consultation rate during week 12 was 6.1 per 100,000 population. This is lower to week 11 (7.7 per 100,000 population). Rates are at baseline activity levels (<10.1 per 100,000 population) (Figure 3.1).

Flu/FLI consultation rates by age groups are shown in Table 5. The highest rate in week 12 was seen in the 15-44 age group (7.5 per 100,000 population).

Flu/FLI consultation rates by Health and Social Care Trust (HSCT) are shown in Table 6. The highest rate in week 12 was seen in the Western Trust (7.8 per 100,000 population).

Since the beginning of the COVID-19 pandemic, the offer of uptake of GP consultations has changed. As a result, consultation rates in the most recent period are unlikely to be directly comparable to pre-pandemic and pandemic years.

Figure 3.1: Northern Ireland GP consultation rates for ‘flu/FLI’ 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.

3.2 Consultation rates for acute respiratory infection (ARI)

The GP ARI consultation rate during week 12 was 99.1 per 100,000 population. This is a decrease from week 11 (117.0 per 100,000 population) (Figure 3.2).

ARI consultation rates by age groups are shown in Table 7. The highest rate in week 12 was seen in the 0-4 age group (389.9 per 100,000 population).

ARI consultation rates by HSCT are shown in Table 8. The highest rate in week 12 was seen in the Belfast Trust (109.3 per 100,000 population).

Figure 3.2: Northern Ireland GP consultation rates for ARI 2021/22 – 2024/25

4.1 Influenza, RSV and COVID-19 care homes outbreaks

There was one COVID-19 outbreak reported in a care home setting in week 12. This is a slight increase from 11 (no outbreaks reported) (Figure 4.1).

Figure 4.1: Weekly number of confirmed influenza, RSV and COVID-19 outbreaks, by year and epidemiological week

5.1 Admissions and occupancy

There were 42 new community-acquired emergency hospital admissions during week 12 (Figure 5.1). This is a decrease from week 11 (n=53). Of the 42 new admissions, 15 were Flu A, 21 were Flu B, two were RSV and four were COVID-19.

The 5-14 age group had the majority of community acquired emergency influenza hospital admissions in week 12 (30.6%). The 75+ age group had the majority of COVID-19 hospital admissions (75.0%, respectively).

Community-acquired emergency influenza and COVID-19 inpatients have decreased slightly whilst RSV inpatients have remained stable. (Figure 5.2).

Figure 5.1: Weekly number of community-acquired emergency influenza, RSV and COVID-19 hospital admissions, by year and epidemiological week

Figure 5.2: Influenza, RSV and COVID-19 community acquired emergency inpatients, by day

6.1 Deaths related to influenza and/or pneumonia

NISRA death statistics are published weekly. From week ending 31 January 2025 these statistics now include a count of deaths related to influenza and/or pneumonia.

The 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 or pneumonia has contributed to a death but was not necessarily the underlying cause of the death.

The latest data is available from Friday 14 March 2025. In week 11, 66 influenza and/or pneumonia related deaths out of 385 deaths were reported (17.1%). This is a decrease from the previous week (73 influenza and/or pneumonia related deaths out of 344 deaths, 21.2%) (Figure 6.1).

Figure 6.1: Weekly deaths and percentage of registered deaths related to influenza and/or pneumonia, to most recent registration week

6.2 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.

The latest data is available from Friday 14 March 2025. In week 11, there was one COVID-19 related death out of 385 deaths reported (0.3%). This is similar to the previous week (no COVID-19 related deaths out of 344 deaths) (Figure 6.2).

Figure 6.2: Weekly deaths and percentage of registered deaths related to COVID-19, to most recent registration week

6.3 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.

7.1 Presentation of data

Unless otherwise stated, data are presented using epidemiological weeks (a standardised method of counting weeks [Monday-Sunday] to allow for the comparison of data year after year). This is dependent on the data available. The data included in this report are the most up to date data available at the time of the report; however, this is subject to change as the data are subject to ongoing quality assurance.

7.2 Virology surveillance

All virology data provided here are preliminary. Virology data for prior weeks, as included in this or future bulletins, are subject to updates based on laboratory returns received after the last report was produced. The current bulletin offers the most current information available.

Rates per 100,000 population are calculated using the NISRA 2021 Mid-Year Population Estimates.

7.3 Primary care surveillance

7.4 Community surveillance

7.5 Secondary care surveillance

7.6 Mortality surveillance

NISRA death statistics are published weekly, and include weekly counts of deaths related to influenza and/or pneumonia (new from 31 January 2025), and deaths related to COVID-19. This enables comparisons with weekly information published by the Office for National Statistics (ONS) covering England and Wales.

The statistics report on deaths where influenza and/or pneumonia, or COVID-19, was mentioned anywhere on the death certificate. As a result, the counts will reflect deaths where these diseases have contributed to a death but was not necessarily the underlying cause of the death.

8.1 Unique episodes of influenza, RSV and COVID-19, by epidemiological week, over a six week period

8.2 Influenza, RSV and COVID-19 episode rates per 100,000 population, by age group, over a six week period

8.3 Influenza, RSV and COVID-19 episode rates per 100,000 population, by local government district, over a six week period

8.4 Total tests and positivity for influenza, RSV and COVID-19, by epidemiological week, over a six week period

8.5 Total sentinel tests and positivity for influenza, RSV and COVID-19, by epidemiological week, over a six week period

8.6 Total non-sentinel tests and positivity for influenza, RSV and COVID-19, by epidemiological week, over a six week period

8.7 Number of sequenced samples for variants in Northern Ireland

This table only shows counts for lineages with 10 or more sequenced samples from epidemiological year-week 2024 - 12 onwards. Lineage counts include provisional and confirmed sequencing samples. Lineage calls are subject to change following analysis of genomic sequence results, which may result in fluctuations in lineage counts.