2.1 Episodes of influenza, RSV and COVID-19

The number of new influenza episodes increased in week 50, with 708 unique episodes identified. There were 476 episodes reported in week 49. The number of new RSV episodes decreased in week 50, with 193 unique episodes identified; 218 episodes were reported in week 49 (Figure 2.1).

Influenza and RSV episode rates by age groups are shown in (Figure 2.2). The highest influenza episode rate in week 50 was in the 0-4 age group (143.3 per 100,000 population). Similarly, the highest RSV episode rate was in the 0-4 age group (131.8 per 100,000 population).

Influenza and RSV episode rates across local government districts (LGD) are shown in (Figure 2.3). Ards and North Down had the highest influenza episode rate in week 50 (56.2 per 100,000 population). Belfast had the highest RSV episode rate (18.0 per 100,000 population).

The number of new COVID-19 episodes remained stable in week 50, with 63 episodes identified compared to 59 in week 49 (Figure 2.1).

COVID-19 episode rates by age groups are shown in (Figure 2.2). The highest COVID-19 episode rate in week 50 was in the 75+ age group (21.8 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 50 (8.5 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 50 there were 2,451 total influenza tests, 722 of which were positive (29.5% positivity). This is an increase from week 49 (22.5% positivity) (Figure 2.4).

There were 1,432 total RSV tests, 198 of which were positive (13.8% positivity). This is a decrease from week 49 (16.8% positivity) (Figure 2.4).

There were 2,401 COVID-19 tests, 70 of which were positive (2.9% positivity). This is a decrease from week 49 (3.2% 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 708 new influenza episodes identified in week 50, 244 were typed as Flu A(H1), nine were Flu A(H3), 443 were Flu A (not subtyped) and 12 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 50, 39 samples were positive for influenza from 64 samples submitted for testing (60.9% positivity) to the Regional Virus Laboratory (RVL). 29 were typed as Flu A(H1), eight were Flu A (not subtyped) and two were Flu B. Three samples were positive for RSV from 64 samples submitted for testing (4.7% positivity). Two samples were positive for COVID-19 from 64 samples submitted for testing (3.3% positivity) (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 50, 685 samples were positive for influenza from 2,391 samples submitted for testing to laboratories across NI (28.7% positivity). 233 were typed as Flu A(H1), 11 were Flu A(H3), 433 were Flu A (not subtyped) and eight were Flu B. 195 samples were positive for RSV from 1,369 samples submitted for testing (14.2% positivity). 68 samples were positive for COVID-19 from 2,345 samples submitted for testing (2.9% 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 25th November 2024, XEC accounted for 60% of all sequenced samples, JN.1 20% with KP and KP.3 10%, 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 reported here. Technical information is published by UKSHA on some specific KP variants online here with a commentary on them here.

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 50 was 21.2 per 100,000 population. This is an increase from week 49 (13.3 per 100,000 population). Rates increased to moderate activity levels (20.5 to <47.4 per 100,000 population) (Figure 3.1).

Flu/FLI consultation rates by age groups are shown in Table 5. The highest rate in week 50 was seen in the 0-4 year old age group (31.0 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 50 was seen in the South Eastern Trust (27.6 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 50 was 206.0 per 100,000 population. This is an increase from week 49 (190.5 per 100,000 population) (Figure 3.2).

ARI consultation rates by age groups are shown in Table 7. The highest rate in week 50 was seen in the 0-4 age group (1,065.1 per 100,000 population).

ARI consultation rates by HSCT are shown in Table 8. The highest rate in week 50 was seen in the Western Trust (231.0 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 Flu A (not subtyped) outbreak reported in a care home setting in week 50 (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 365 new community-acquired emergency hospital admissions during week 50 (Figure 5.1). This was an increase compared with week 49 (n=333). Of the 365 new admissions, 244 were Flu A, six were Flu B, 99 were RSV and 16 were COVID-19. The 75+ age group had the majority of community acquired emergency influenza hospital admissions in week 50 (27.6%). The 0-4 age group had the majority of RSV hospital admissions (78.8%), and the 75+ age group had the majority of COVID-19 hospital admissions (68.8%).

Community acquired emergency influenza inpatients continued to increase while RSV and COVID inpatients has 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 Medical certificate of cause of death for respiratory-associated deaths

The NI Statistics and Research Agency (NISRA) provides the weekly number of respiratory-associated deaths and the proportion of all-cause registered deaths (by week of death registration, not by week of death).

Respiratory-associated deaths include those that are attributable to influenza, other respiratory infections or their complications. This includes “bronchiolitis, bronchitis, influenza or pneumonia” keywords recorded on the death certificate.

In week 50, 100 respiratory associated deaths out of 387 all-cause deaths were reported (25.8%). This is higher to the same period in 2023/24 (84 respiratory associated deaths out of 374 all-cause deaths, 22.5%) (Figure 6.1).

Figure 6.1: Weekly number of deaths with respiratory keywords, to current registration week

6.2 Medical certificate of cause of death for COVID-19 related deaths

NISRA provide the weekly number of COVID-19 registered deaths each Friday. In week 49, five COVID-19 related deaths out of 362 all-cause deaths were reported (1.4%). This is an increase compared with the previous week (three COVID-19 related deaths out of 373 all-cause deaths, 0.8%) (Figure 6.2). Further detail can be found online here.

Figure 6.2: Weekly number of COVID-19 related deaths, to current 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) which can be found online here.

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 can be found online here.

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

PHA report weekly counts of selected respiratory infection death registrations in NI, as supplied by NISRA for influenza and RSV. PHA report weekly counts of COVID-19 death registrations in NI, as published by NISRA online here. Deaths occurring in NI are registered on the NI General Register Office’s Registration System (NIROS). Provisional data on deaths registered in each week (ending on a Friday) are compiled at the end of the following week. The data presented here is based on registrations of deaths, not occurrences. The majority of deaths are registered within five days in NI. The selected respiratory infections include deaths due to influenza, bronchitis, bronchiolitis, and pneumonia. These figures may be impacted by General Registration Office closures over public holidays.

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 2023 - 50 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.