2.1 Episodes of influenza, RSV and COVID-19

The number of new influenza episodes decreased in week 02, with 474 unique episodes identified. There were 704 episodes reported in week 01. The number of new RSV episodes decreased in week 02, with 89 unique episodes identified; 128 episodes were reported in week 01 (Figure 2.1).

Influenza and RSV episode rates by age groups are shown in (Figure 2.2). The highest influenza episode rate in week 02 was in the 75+ age group (101.0 per 100,000 population). The highest RSV episode rate was in the 0-4 age group (34.5 per 100,000 population).

Influenza and RSV episode rates across local government districts (LGD) are shown in (Figure 2.3). Newry, Mourne and Down had the highest influenza and RSV episode rate in week 02 (32.4 per 100,000 population and 7.7 per 100,000 population, respectively).

The number of new COVID-19 episodes decreased in week 02, with 31 episodes identified compared to 63 in week 01 (Figure 2.1).

COVID-19 episode rates by age groups are shown in (Figure 2.2). The highest COVID-19 episode rate in week 02 was in the 75+ age group (8.6 per 100,000 population).

COVID-19 episode rates across LGD are shown in (Figure 2.3). Lisburn and Castlereagh had the highest COVID-19 episode rate in week 02 (5.4 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 02 there were 2,464 total influenza tests, 493 of which were positive (20.0% positivity). This is a decrease from week 01 (26.3% positivity) (Figure 2.4).

There were 1,451 total RSV tests, 92 of which were positive (6.3% positivity). This is a decrease from week 01 (8.4% positivity) (Figure 2.4).

There were 2,363 COVID-19 tests, 35 of which were positive (1.5% positivity). This is a decrease from week 01 (2.7% 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 474 new influenza episodes identified in week 02, 162 were typed as Flu A (H1), 24 were Flu A (H3), 205 were Flu A (not subtyped) and 83 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 02, 45 samples were positive for influenza from 99 samples submitted for testing (45.5% positivity) to the Regional Virus Laboratory (RVL). 25 were typed as Flu A (H1), three were Flu A (H3), five were Flu A (not subtyped) and 12 were Flu B. Six samples were positive for RSV from 99 samples submitted for testing (6.1% positivity). Two samples were positive for COVID-19 from 99 samples submitted for testing(2.0% 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 02, 448 samples were positive for influenza from 2,367 samples submitted for testing to laboratories across NI (18.9% positivity). 152 were typed as Flu A (H1), 21 were Flu A (H3), 204 were Flu A (not subtyped) and 71 were Flu B. 86 samples were positive for RSV from 1,352 samples submitted for testing (6.4% positivity). 33 samples were positive for COVID-19 from 2,281 samples submitted for testing (1.5% 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 02 was 32.9 per 100,000 population. This is a decrease from week 01 (38.5 per 100,000 population). Rates are at 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 02 was seen in the 75+ year old age group (47.4 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 02 was seen in the Western Trust (48.3 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 02 was 147.2 per 100,000 population. This is a decrease from week 01 (178.2 per 100,000 population) (Figure 3.2).

ARI consultation rates by age groups are shown in Table 7. The highest rate in week 02 was seen in the 0-4 age group (375.5 per 100,000 population).

ARI consultation rates by HSCT are shown in Table 8. The highest rate in week 02 was seen in the South Eastern Trust (165.0 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 were six Flu A (not subtyped) outbreaks reported in a care home setting in week 02. This is a decrease from week 01 outbreaks. (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 225 new community-acquired emergency hospital admissions during week 02 (Figure 5.1). This is a decrease from week 01 (n=368). Of the 225 new admissions, 163 were Flu A, 19 were Flu B, 36 were RSV and seven were COVID-19. The 75+ age group had the majority of community acquired emergency influenza hospital admissions in week 02 (44.5%). The 0-4 age group had the majority of RSV hospital admissions (66.7%), and the 75+ age group had the majority of COVID-19 hospital admissions (57.1%).

Community acquired emergency influenza inpatients are decreasing while RSV and COVID-19 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 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 02, 175 respiratory associated deaths out of 544 all-cause deaths were reported (32.2%). This is higher to the same period in 2023/24 (134 respiratory associated deaths out of 462 all-cause deaths, 29.0%) (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, with the latest data available from Friday 27th December 2024. In week one, three COVID-19 related deaths out of 416 all-cause deaths were reported (0.7%). This is lower than the previous week (three COVID-19 related deaths out of 193 all-cause deaths, 1.6%) (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 2024 - 02 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.