2.1 Episodes of influenza, RSV and COVID-19

The number of new influenza episodes decreased in week 45, with 63 unique episodes identified. There were 65 episodes reported in week 44. The number of new RSV episodes increased in week 45, with 88 unique episodes identified; 53 episodes were reported in week 44 (Figure 2.1).

Influenza and RSV episode rates by age groups are shown in (Figure 2.2). The highest influenza and RSV episode rate in week 45 were in the 0-4 age group (15.0 and 70.8 per 100,000 population, respectively).

Influenza and RSV episode rates across local government districts (LGD) are shown in (Figure 2.3). Belfast had the highest influenza episode rate in week 45 (5.8 per 100,000 population). Fermanagh and Omagh had the highest RSV episode rate in week 45 (11.1 per 100,000 population).

The number of new COVID-19 episodes decreased in week 45, with 44 episodes identified compared to 69 in week 44 (Figure 2.1).

COVID-19 episode rates by age groups are shown in (Figure 2.2). The highest COVID-19 episode rate in week 45 was in the 75+ age group (17.2 per 100,000 population).

COVID-19 episode rates across LGD are shown in (Figure 2.3). Armagh City, Banbridge and Craigavon had the highest COVID-19 episode rate in week 45 (5.5 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 45 there were 1,268 total influenza tests, 63 of which were positive (5.0% positivity). This is similar to week 44 (4.7% positivity) (Figure 2.4).

There were 864 total RSV tests, 88 of which were positive (10.2% positivity). This is an increase from week 44 (6.1% positivity) (Figure 2.4).

There were 1,315 COVID-19 tests, 54 of which were positive (4.1% positivity). This is a decrease from week 44 (5.6% 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 63 new influenza episodes identified in week 45, 21 were typed as Flu A(H1), two were Flu A(H3), 39 were Flu A (not subtyped) and one was 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 (n=52; ~18% population representative) to provide information about virus activity across NI.

In week 45, two samples (Flu A(H1) and Flu A(H3)) were positive for influenza from 17 samples submitted for testing to the Regional Virus Laboratory (RVL) (11.8% positivity). No samples were positive for RSV from 17 samples submitted for testing. (Table 1).

Total sentinel cases of influenza and RSV by age group for the previous year are shown in (Figure 2.6) and (Figure 2.7) 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

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 45, 61 samples were positive for influenza from 1,251 samples submitted for testing to laboratories across NI (4.9% positivity). 21 were typed as Flu A(H1), one was Flu A(H3), 38 were Flu A (not subtyped) and one was Flu B. 88 samples were positive for RSV from 847 samples submitted for testing (10.4% positivity) (Table 3).

Total non-sentinel cases of influenza and RSV by age group for the previous year are shown in (Figure 2.6) and (Figure 2.7) 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 2.8: Weekly non-sentinel influenza cases, by age group, by epidemiological week

Figure 2.9: Weekly non-sentinel RSV 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 14th October 2024, KP.3 accounts for 51% of all sequenced samples, XEC 34%, KP 2% and JN.1 2%. 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 2.10: 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 45 was 4.3 per 100,000 population. This is an increase from week 44 (3.8 per 100,000 population). Activity remains at baseline 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 45 was seen in the 75+ year old age group (5.3 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 45 was seen in the Western Trust (6.4 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 45 was 128.7 per 100,000 population. This is an increase from week 44 (120.9 per 100,000 population) (Figure 3.2).

ARI consultation rates by age groups are shown in Table 7. The highest rate in week 45 was seen in the 0-4 age group (692.7 per 100,000 population).

ARI consultation rates by HSCT are shown in Table 8. The highest rate in week 45 was seen in the Western Trust (152.4 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 no respiratory outbreaks in care home settings in week 45 (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 100 new community-acquired emergency hospital admissions during week 45 (Figure 5.1). This is an increase from week 44 (n=86). Of the 100 new admissions, 29 were Flu A, one Flu B, 58 were RSV and 12 were COVID-19. The 0-4 age groups had the majority of community acquired emergency influenza hospital admissions in week 45 (36.7%). The 0-4 age group had the majority of community acquired emergency RSV hospital admissions in week 45 (89.7%). The 75+ age group had the majority of community acquired emergency COVID-19 hospital admissions in week 45 (50.0%).

Community acquired emergency influenza and RSV inpatients continues to increase but remains at low levels and there has been a stable trend in the number of community acquired emergency COVID-19 inpatients in recent weeks (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 45, 78 respiratory associated deaths out of 350 all-cause deaths were reported (22.3%). This is lower to the same period in 2023/24 (92 respiratory deaths out of 386) all-cause deaths, 23.8% (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 44, eight COVID-19 related deaths out of 336 all-cause deaths were reported (2.4%). This is similar to the previous week (seven COVID-19 related deaths out of 326 all-cause deaths, 2.1% (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 and RSV, by epidemiological week, over a six week period

8.6 Total non-sentinel tests and positivity for influenza and RSV, 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 - 45 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.