Virology surveillance
Episodes of influenza, RSV and COVID-19
The number of new influenza episodes increased in week 40, with 24 unique episodes identified. There were 12 episodes reported in week 39. There were eight new RSV episodes identified in week 40, which is an increase to week 39 when four episodes were identified (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 40 was in the 0-4 age group (both 4.4 per 100,000 population).
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 40 (3.3 per 100,000 population). Derry City and Strabane, and Lisburn and Castlereagh had the highest RSV episode rate in week 40 (both 1.3 per 100,000 population).
The number of new COVID-19 episodes remained similar in week 40, with 184 unique episodes identified compared with 182 in week 39 (Figure 2.1).
COVID-19 episode rates by age groups are shown in (Figure 2.2). The highest COVID-19 episode rate in week 40 was in the 75+ age group (58.1 per 100,000 population).
COVID-19 episode rates across LGD are shown in (Figure 2.3). Mid Ulster had the highest COVID-19 episode rate in week 40 (13.9 per 100,000 population).
Supplementary tables of unique episodes and weekly episode rates are shown at the end of this report.
Testing and positivity (%)
In week 40 there were 1,820 influenza tests, 24 of which were positive (1.3% positivity). This is an increase to week 39 (0.7% positivity) (Figure 2.4).
There were 994 RSV tests, of which eight were positive (0.8% positivity). This is an increase to week 39 (0.4% positivity) (Figure 2.4).
There were 1,884 COVID-19 tests, 205 of which were positive (10.9% positivity). This is a slight decrease to week 39 (11.4% positivity) (Figure 2.4).
There were 305 rhinovirus tests, 63 of which were positive (20.7% positivity). This is a slight increase to week 39 (20.2% positivity) (Figure 2.4).
A supplementary table of testing and positivity is shown at the end of this report.
Shading represents 95% confidence intervals.
In week 40 there were 305 adenovirus tests, seven of which were positive (2.3% positivity). This is an increase to week 39 (1.1% positivity) (Figure 2.5).
There were 305 parainfluenza tests, four of which were positive (1.3% positivity). This is an increase to week 39 (0.4% positivity) (Figure 2.5).
There were 305 human metapneumovirus (hMPV) tests, one of which was positive (0.3% positivity). This is a decrease to week 39 (1.1% positivity) (Figure 2.5).
Shading represents 95% confidence intervals.
Influenza sub-typing
Of the 24 new influenza episodes identified in week 40, two were typed as Flu A (H1), two were Flu A (H3), 19 were Flu A (not subtyped) and one was Flu B (Figure 2.6).
A supplementary table of influenza sub-typing is shown at the end of this report.
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 (~16% population representative) to provide information about virus activity across NI.
In week 40, one sample was positive for Flu B (3.3% positivity) from 30 samples submitted for testing to the Regional Virus Laboratory (RVL). No samples were positive for RSV or COVID-19 from 30 samples 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 2.7), (Figure 2.8) and (Figure 2.9), and cumulatively for the 2025/26 influenza season in Table 2.
A supplementary table of testing and positivity is shown at the end of this report.
Table 1. Total sentinel tests and positivity for Influenza, RSV and COVID-19, current week |
|---|
|
| Total Tests | Total Positives | Positivity (%) |
|---|
2025 - 40 | Influenza | 30 | 1 | 3.33 |
2025 - 40 | RSV | 30 | 0 | 0.00 |
2025 - 40 | COVID-19 | 30 | 0 | 0.00 |
Table 2. Total sentinel cases of Influenza, RSV and COVID-19 by age group, Week 40 - current week, 2025/26 |
|---|
| 0-4 | 5-14 | 15-44 | 45-64 | 65-74 | 75+ | Total |
|---|
Flu A (H1) | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Flu A (H3) | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Flu A (not subtyped) | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Flu B | 0 | 0 | 0 | 1 | 0 | 0 | 1 |
RSV | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
COVID-19 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
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 40, 23 samples were positive for influenza from 1,790 samples submitted for testing to laboratories across NI (1.3% positivity). Of these, two were typed as Flu A (H1), two were Flu A (H3), and 19 were Flu A (not subtyped).
For RSV, eight samples were positive from 964 samples submitted for testing (0.8% positivity).
For COVID-19, 205 samples were positive from 1,854 samples submitted for testing (11.1% positivity) (Table 3).
Total non-sentinel cases of influenza, RSV and COVID-19 by age group for the previous year are shown in (Figure 2.7), (Figure 2.8) and (Figure 2.12), and cumulatively for the 2025/26 influenza season in Table 4.
A supplementary table of testing and positivity is shown at the end of this report.
Table 3. Total non-sentinel tests and positivity for Influenza, RSV and COVID-19, current week |
|---|
|
| Total Tests | Total Positives | Positivity (%) |
|---|
2025 - 40 | Influenza | 1,790 | 23 | 1.28 |
2025 - 40 | RSV | 964 | 8 | 0.83 |
2025 - 40 | COVID-19 | 1,854 | 205 | 11.06 |
Table 4. Total non-sentinel cases of Influenza, RSV and COVID-19 by age group, Week 40 - current week, 2025/26 |
|---|
| 0-4 | 5-14 | 15-44 | 45-64 | 65-74 | 75+ | Total |
|---|
Flu A (H1) | 1 | 0 | 0 | 1 | 0 | 0 | 2 |
Flu A (H3) | 0 | 0 | 1 | 0 | 0 | 1 | 2 |
Flu A (not subtyped) | 4 | 0 | 7 | 0 | 4 | 4 | 19 |
Flu B | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
RSV | 5 | 0 | 0 | 1 | 1 | 1 | 8 |
COVID-19 | 19 | 5 | 23 | 39 | 24 | 95 | 205 |
SARS-CoV-2 variants
In the 8 weeks 28 July 2025 to 21 September 2025, 253 COVID-19 samples were sequenced. Of these, 80 were XFG (31.6% of all sequenced samples), 71 were XFG.3 (28.1% of all sequenced samples), 40 were NB.1.8.1 (15.8% of all sequenced samples), 7 were KP (2.8% of all sequenced samples), 6 were LP.8.1 (2.4% of all sequenced samples), 4 were BA.2 (1.6% of all sequenced samples), and 3 were XEC and JN.1 (both 1.2% of all sequenced samples). 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.
Parent lineages displayed are subject to change based on lineages under monitoring by the UKHSA horizon scanning team.
Recombinant refers to any recombinant lineage, starting “X”, that does not fall under the parent lineage of a defined variant.
Primary care surveillance
Consultation rates for influenza/influenza-like-illness (‘flu/ILI’)
The general practice (GP) flu/ILI consultation rate during week 40 was 5.1 per 100,000 population. This is an increase to week 39 (4.1 per 100,000 population). Rates are at baseline activity levels (<10.7 per 100,000 population) (Figure 3.1).
The highest rate in week 40 was in the 75+ age group (7.1 per 100,000 population) (Figure 3.2).
The highest rate in week 40 was in the Western Trust (7.3 per 100,000 population) (Figure 3.3).
Supplementary tables of GP consultation rates are shown at the end of this report.
The baseline MEM threshold for Northern Ireland is <10.7 per 100,000 population for 2025-26. Low activity is 10.7 to <25.8, moderate activity 25.8 to <55.2, high activity 55.2 to <77.1 and very high activity is >77.1 per 100,000 population.
Consultation rates for acute respiratory infection (ARI)
The GP ARI consultation rate during week 40 was 158.5 per 100,000 population. This is similar to week 39 (157.9 per 100,000 population) (Figure 3.4).
The highest rate in week 40 was in the 0-4 age group (457.7 per 100,000 population) (Figure 3.5).
The highest rate in week 40 was in the Western Trust (198.2 per 100,000 population) (Figure 3.6).
Supplementary tables of GP consultation rates are shown at the end of this report.
Consultation rates for COVID-19
The GP COVID-19 consultation rate during week 40 was 5.1 per 100,000 population. This is an increase to week 39 (4.2 per 100,000 population) (Figure 3.7).
The highest rate in week 40 was in the 75+ age group (15.9 per 100,000 population) (Figure 3.8).
The highest rate in week 40 was in the South Eastern Trust (6.6 per 100,000 population) (Figure 3.9).
Supplementary tables of GP consultation rates are shown at the end of this report.
Methods
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.
Virology surveillance
All virology data provided here are preliminary. Virology data for prior weeks, as included in this or future reports, are subject to updates based on laboratory returns received after the last report was produced. The current report offers the most current information available.
Rates per 100,000 population are calculated using the NISRA 2021 Mid-Year Population Estimates.
Episodes of infection
Influenza
Influenza episodes are defined by a 42-day (6-week) period from the date of the first positive test result (utilising any test method, including PCR and Point of Care Tests, or source of sample, including hospital, GP, other source), with the episode beginning with the earliest positive specimen date. Subsequent positive specimen dates for the same individual within 42 days of the last are included in the one episode. Positive specimens for the same individual more than 42 days after the last are counted in a separate episode.
RSV
RSV episodes are defined by a 14-day (2-week) period from the date of the first positive test result (utilising any test method, including PCR and Point of Care Tests, or source of sample, including hospital, GP, other source), with the episode beginning with the earliest positive specimen date. Subsequent positive specimen dates for the same individual within 14 days of the last are included in the one episode. Positive specimens for the same individual more than 14 days after the last are counted in a separate episode.
COVID-19
COVID-19 episodes are defined by a rolling 90-day period between positive test results (utilising any test method, including PCR and Point of Care Tests, or source of sample, including hospital, GP, other source), with the episode beginning with the earliest positive specimen date. Subsequent positive specimen dates for the same individual within 90 days of the last are included in the one episode. Positive specimens for the same individual more than 90 days after the last are counted in a separate episode.
Testing and positivity (%)
Influenza, RSV, COVID-19, rhinovirus, adenovirus, parainfluenza and human metapneumovirus
Instead of utilising an episode-based approach, the data is analysed on an epidemiological week basis. Within each epidemiological week, an individual is limited to one influenza test, whether positive or negative. If an individual tests positive for influenza during a specific epidemiological week and subsequently tests positive again within the same week, the second positive test is not counted. Regardless of whether it occurs before or after a negative test within the same epidemiological week, a positive test always takes precedence and is recorded. Similarly, only the first test of multiple negative results is counted for each individual within any given epidemiological week. This helps prevent the double-counting of tests, particularly for individuals who may be hospitalised and routinely tested.
Weekly test positivity is calculated as the proportion of positive tests to total tests conducted. To estimate the uncertainty around these proportions, 95% confidence intervals (CIs) were computed using the Wilson score interval. The Wilson method is a binomial proportion CI that avoids the limitations of some other methods, particularly for small sample sizes or extreme proportions. It provides more accurate bounds by incorporating the standard error and adjusting for asymmetry in the binomial distribution. This method ensures that the plotted CIs reflect the true statistical uncertainty in weekly positivity estimates.
The same methodology is applied when analysing RSV, COVID-19, rhinovirus, adenovirus, parainfluenza and human metapneumovirus data.
Sentinel surveillance
The Public Health Agency works with GPs to deliver a community-based surveillance programme for respiratory infections in NI. The programme provides valuable intelligence about the circulation of respiratory viruses in NI to inform health and social care system planning and preparedness. Participation involves taking nasal/throat swabs from some symptomatic patients who agree to have a swab, and who attend (in person) with ILI, ARI or suspected COVID-19. Testing is opportunistic and within 10 days of symptom onset. Swabs are tested for influenza, RSV and COVID-19 at the RVL and surveillance is year-round.
SARS-CoV-2 genomics
A subset of SARS-CoV-2 positive PCR samples are sent to sequencing laboratories in Belfast Health and Social Care Trust and Queen’s University Belfast for sequencing. On 29th November the lineage assignment algorithm was switched from PangoLEARN to UShER for lineage counts. PangoLEARN uses a machine learning algorithm, whereas UShER uses phylogenetic placement and produces fewer unassigned lineages. This switch has been applied retrospectively, therefore total counts for all lineages have been affected. A more detailed COVID-19 Genomics Bulletin containing a further breakdown of sub-lineages is published weekly.
Primary care surveillance
Consultation rates for influenza/influenza-like-illness (‘flu/ILI’), acute respiratory infection (ARI) and COVID-19
GP in-hours consultation data with ~95% coverage of the NI population is auto-extracted weekly from the General Practitioner Intelligence Platform (GPIP). This data includes weekly aggregate consultations for ‘flu/ILI’, ARI, and COVID-19, and includes weekly registered patients. The data is available for different Health and Social Care Trusts, and by age and sex.
Secondary care surveillance
Admissions and occupancy
It is not currently possible for this report to distinguish emergency from other types of admission for each Trusts hospital data following the introduction of a new electronic healthcare record (EPIC). This was introduced in the SEHSCT on 06/11/2023; BHSCT on 06/06/2024, NHSCT on 07/11/2024, and WHSCT and SHSCT on 28/04/2025. For this report, all community-acquired admissions are included from the respective dates above for each Trust, which will include non-emergency admissions (which are a small minority of the total admissions reported). Only admissions where the method of admission was ‘Emergency’ are counted before these dates for each Trust. Work is ongoing to adapt systems to new data sources and re-instate differentiation of emergency admissions. Ongoing developmental and quality assurance work may result in adjustments to figures.
Influenza and RSV
Community-acquired influenza and RSV emergency admissions to acute hospitals are estimated by combining data from the Patient Administration System (PAS), EPIC and virological reports in the Northern Ireland Health Analytics Platform (NIHAP). Admissions are counted where there was a positive test up to seven days before admission or up to one day after admission, and the method of admission was ‘Emergency’. The number of inpatients is counted at midnight. Admissions and occupancy refer to the first admission per infection episode.
COVID-19
Community-acquired COVID-19 emergency admissions are estimated by combining data from from PAS, EPIC and virological reports in NIHAP. Admissions are counted where there was a positive PCR or lateral flow test up to 14 days before admission or up to one day after admission. The number of inpatients is counted at midnight. Admissions and occupancy refer to the first admission per infection episode, including transfers between hospitals. The method used in this report is different to that previously reported by the Department of Health’s COVID-19 dashboard, which used administrative coding to identify COVID-19 admissions.
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.
