2.1 Episodes of influenza, RSV and COVID-19

The number of new influenza episodes increased in week 42, with 42 unique episodes identified. There were 18 episodes reported in week 41. The number of new RSV episodes increased in week 42, with 26 unique episodes identified; 15 episodes were reported in week 41 (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 42 were in the 0-4 age group (15.0 and 22.1 per 100,000 population, respectively).

Influenza and RSV episode rates across local government districts (LGD) are shown in (Figure 2.3). Lisburn and Castlereagh had the highest influenza episode rate in week 42 (6.7 per 100,000 population). Lisburn and Castlereagh, and Newry, Mourne and Down had the highest RSV episode rate in week 42 (both 2.7 per 100,000 population).

The number of new COVID-19 episodes increased in week 42, with 191 episodes identified compared to 161 in week 41 (Figure 2.1).

COVID-19 episode rates by age groups are shown in (Figure 2.2). The highest COVID-19 episode rate in week 42 was in the 75+ age group (47.5 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 42 (15.5 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 42 there were 1,350 total influenza tests, 42 of which were positive (3.1% positivity). This is an increase from week41 (1.5% positivity) (Figure 2.4).

There were 866 total RSV tests, 26 of which were positive (3.0% positivity). This is an increase from week 41 (1.6% positivity) (Figure 2.4).

There were 1,392 COVID-19 tests, 176 of which were positive (12.6% positivity). This is a increase from week 41 (10.8% 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 42 new influenza episodes identified in week 42, 12 were typed as Flu A(H1), five were Flu A(H3), 22 were Flu A (not subtyped) and three 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 (n=52; ~18% population representative) to provide information about virus activity across NI.

In week 42, four samples were positive for influenza from 11 samples submitted for testing to the Regional Virus Laboratory (RVL) (36.4% positivity). Three were typed as Flu A(H1) and one was Flu A(H3). One sample was positive for RSV from 11 samples submitted for testing (9.1% positivity) (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 42, 38 samples were positive for influenza from 1,339 samples submitted for testing to laboratories across NI (2.8% positivity). 10 were typed as Flu A(H1), four were Flu A(H3), 22 were Flu A (not subtyped) and two were Flu B. 25 samples were positive for RSV from 855 samples submitted for testing (2.9% 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 30th September 2024, KP.3 accounts for 69% of all sequenced samples, XEC 17%, KP 4% 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 42 was 3.9 per 100,000 population. This is an increase from week 41 (3.1 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 42 was seen in the 15-44 age group (5.1 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 42 was seen in the South Eastern Trust (7.2 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 42 was 127.7 per 100,000 population. This is an increase from week 41 (123.1 per 100,000 population) (Figure 3.2).

ARI consultation rates by age groups are shown in Table 7. The highest rate in week 42 was seen in the 0-4 age group (617.5 per 100,000 population).

ARI consultation rates by HSCT are shown in Table 8. The highest rate in week 42 was seen in the Western Trust (158.2 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 three COVID-19 outbreaks reported in a care home setting in week 42 (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 81 new community-acquired emergency hospital admissions during week 42 (Figure 5.1). This is an increase to week 41 (n=51). Of the 81 new admissions, 18 were Flu A, 18 were RSV and 45 were COVID-19. The 0-4 and 5-14 age groups had the majority of community acquired emergency influenza hospital admissions in week 42 (both 27.8%). The 0-4 age group had the majority of community acquired emergency RSV hospital admissions in week 42 (100.0%). The 75+ age group had the majority of community acquired emergency COVID-19 hospital admissions in week 42 (46.7%).

Community acquired emergency influenza and RSV inpatients increased 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 42, 85 respiratory associated deaths out of 372 all-cause deaths were reported (22.8%). This is lower to the same period in 2023/24 (86 respiratory deaths out of 310 all-cause deaths, 27.7% (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 41, four COVID-19 related deaths out of 316 all-cause deaths were reported (1.3%). This is a decrease from the previous week (six COVID-19 related deaths out of 298 all-cause deaths, 2.0% (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 - 42 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.