2.1 Episodes of influenza, RSV and COVID-19

The number of new influenza episodes remained stable in week 19, with 23 unique episodes reported. There were 27 episodes reported in week 18. There were nine new RSV episodes reported in week 19, which is similar to week 18 when six episodes were identified (Figure 2.1).

Influenza and RSV episode rates by age groups are shown in (Figure 2.2). The highest influenza episode rate in week 19 was in the 0-4 age group (2.8 per 100,000 population). The highest RSV episode rate in week 19 was also in the 0-4 age group (7.5 per 100,000 population).

Influenza and RSV episode rates across local government districts (LGD) are shown in (Figure 2.3). Mid and East Antrim had the highest influenza episode rate in week 19 (2.1 per 100,000 population). Belfast had the highest RSV episode rate in week 19 (1.1 per 100,000 population).

The number of new COVID-19 episodes remained stable in week 19, with three unique episodes reported. There were two episodes reported in week 18 (Figure 2.1).

COVID-19 episode rates by age groups are shown in (Figure 2.2). The highest COVID-19 episode rate in week 19 was in the 0-4 age group (0.9 per 100,000 population).

COVID-19 episode rates across LGD are shown in (Figure 2.3). Causeway Coast and Glens and Derry City and Strabane had the highest COVID-19 episode rate in week 19 (both 0.7 per 100,000 population).

Supplementary tables of unique episodes and weekly episode rates are shown at the end of this report.

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 and epidemiological week

Figure 2.3: Weekly episode rates of influenza, RSV and COVID-19 per 100,000 population, by local government district and epidemiological week

2.2 Testing and positivity (%)

In week 19 there were 1,511 influenza tests, 24 of which were positive (1.6% positivity). This is a slight decrease to week 18 (1.8% positivity) (Figure 2.4). Influenza positivity in week 19 was highest in the 15-44 age group (6.6% positivity) (Figure 2.5).

There were 971 RSV tests, nine of which were positive (0.9% positivity). This is a slight increase to week 18 (0.7% positivity) (Figure 2.4). RSV positivity in week 19 was highest in the 0-4 age group (4.9% positivity) (Figure 2.5).

There were 1,494 COVID-19 tests, three of which were positive (0.2% positivity). This is similar to week 18 (0.1% positivity) (Figure 2.4). COVID-19 positivity in week 19 was highest in the 5-14 age group (1.1% positivity) (Figure 2.5).

Supplementary tables of testing and positivity are shown at the end of this report.

Figure 2.4: Weekly positivity for influenza, RSV and COVID-19, by epidemiological week

Shading represents 95% confidence intervals.

Figure 2.5: Weekly positivity for influenza, RSV and COVID-19, by age group and epidemiological week

Shading represents 95% confidence intervals.

In week 19 there were 422 rhinovirus tests, 67 of which were positive (15.9% positivity). This is a decrease to week 18 (19.6% positivity) (Figure 2.6).

There were 422 adenovirus tests, 24 of which were positive (5.7% positivity). This is a decrease to week 18 (6.2% positivity) (Figure 2.6).

There were 422 parainfluenza tests, 14 of which were positive (3.3% positivity). This is similar to week 18 (3.4% positivity) (Figure 2.6).

There were 422 human metapneumovirus (hMPV) tests, nine of which were positive (2.1% positivity). This is an increase from week 18 (0.4% positivity) (Figure 2.6).

Figure 2.6: Weekly positivity for rhinovirus, adenovirus, parainfluenza and Human metapneumovirus, by year and epidemiological week

Shading represents 95% confidence intervals.

2.3 Influenza sub-typing

Of the 23 new influenza episodes identified in week 19, one was typed as influenza A (H1), four were influenza A (not subtyped) and 18 were influenza B (Figure 2.7).

A supplementary table of influenza sub-typing is shown at the end of this report.

Figure 2.7: 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 (~15% population representative) to provide information about virus activity across Northern Ireland.

In week 19, two samples were positive for influenza B from seven samples submitted for testing to the Regional Virus Laboratory (RVL) (28.6% positivity). No samples were positive for RSV or COVID-19 from seven 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 2.8), (Figure 2.9) and (Figure 2.10), 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.

Figure 2.8: Weekly sentinel influenza cases, by age group and epidemiological week

Figure 2.9: Weekly sentinel RSV cases, by age group and epidemiological week

Figure 2.10: Weekly sentinel COVID-19 cases, by age group and 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 Northern Ireland.

In week 19, 22 samples were positive for influenza from 1,504 samples submitted for testing to laboratories across Northern Ireland (1.5% positivity). Of these, one was typed as influenza A (H1), four were influenza A (not subtyped) and 17 were influenza B. Nine samples were positive for RSV from 964 samples submitted for testing (0.9% positivity). Three samples were positive for COVID-19 from 1,487 samples submitted for testing (0.2% positivity) (Table 3).

Total non-sentinel cases of influenza, RSV and COVID-19 by age group for the previous year are shown in (Figure 2.8), (Figure 2.9) and (Figure 2.13), 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.

Figure 2.11: Weekly non-sentinel influenza cases, by age group and epidemiological week

Figure 2.12: Weekly non-sentinel RSV cases, by age group and epidemiological week

Figure 2.13: Weekly non-sentinel COVID-19 cases, by age group and epidemiological week

2.6 SARS-CoV-2 variants

In the 8 weeks 02 March 2026 to 26 April 2026, 21 COVID-19 samples were sequenced. Of these, 11 were BA.3.2 (52.4% of all sequenced samples), 5 were XFG (23.8% of all sequenced samples), 2 were BA.3 (9.5% of all sequenced samples) and 1 sample each was JN.1 and NB.1.8.1 (both 4.8% 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.

Figure 2.14: 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/ILI’)

The general practice (GP) flu/ILI consultation rate during week 19 was 2.7 per 100,000 population. This is similar to week 18 (2.9 per 100,000 population). Rates are at baseline activity levels (<10.7 per 100,000 population) (Figure 3.1).

The highest rate in week 19 was in the 15-44 age group (3.6 per 100,000 population) (Figure 3.2).

The highest rate in week 19 was in the Western Trust (5.6 per 100,000 population) (Figure 3.3).

Supplementary tables of GP consultation rates are shown at the end of this report.

Figure 3.1: Northern Ireland GP consultation rates for ‘flu/ILI’, 2021/22 – 2024/25

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.

Figure 3.2: GP consultation rates for ‘flu/ILI’, by age group, 2022/23 – 2025/26

Figure 3.3: GP consultation rates for ‘flu/ILI’, by HSCT, 2022/23 – 2025/26

3.2 Consultation rates for acute respiratory infection (ARI)

The GP ARI consultation rate during week 19 was 143.3 per 100,000 population. This is a decrease to week 18 (164.4 per 100,000 population) (Figure 3.4).

The highest rate in week 19 was in the 0-4 age group (562.0 per 100,000 population) (Figure 3.5).

The highest rate in week 19 was in the Western Trust (224.2 per 100,000 population) (Figure 3.6).

Supplementary tables of GP consultation rates are shown at the end of this report.

Figure 3.4: Northern Ireland GP consultation rates for ARI, 2022/23 – 2025/26

Figure 3.5: GP consultation rates for ARI, by age group, 2022/23 – 2025/26

Figure 3.6: GP consultation rates for ARI, by HSCT, 2022/23 – 2025/26

3.3 Consultation rates for COVID-19

The GP COVID-19 consultation rate during week 19 was 0.2 per 100,000 population. This is the same as week 18 (0.2 per 100,000 population) (Figure 3.7).

The highest rate in week 19 was in the 45-64 year old age groups (0.6 per 100,000 population) (Figure 3.8).

The highest rate in week 19 was in the Western Trust (0.6 per 100,000 population) (Figure 3.9).

Supplementary tables of GP consultation rates are shown at the end of this report.

Figure 3.7: Northern Ireland GP consultation rates for COVID-19, 2022/23 – 2025/26

Figure 3.8: GP consultation rates for COVID-19, by age group, 2022/23 – 2025/26

Figure 3.9: GP consultation rates for COVID-19, by HSCT, 2022/23 – 2025/26

4.1 Influenza, RSV and COVID-19 care homes outbreaks

There were no confirmed outbreaks reported in care home settings to the Public Health Agency (PHA) Health Protection Acute Response Duty Room in week 19. This is consistent with 18 (Figure 4.1).

Figure 4.1: Weekly number of confirmed influenza, RSV and COVID-19 outbreaks, by epidemiological week

5.1 Admissions and occupancy

There were 11 new community-acquired emergency hospital admissions during week 19 (Figure 5.1). Of these, two were influenza A, four were influenza B and five were RSV. In week 18 there were seven hospital admissions. Of these, one was influenza A, four were influenza B and two were RSV.

Community-acquired emergency hospital admission rates in week 19 were highest in the 0-4 age group for both influenza (0.9 per 100,000 population) and RSV (4.7 per 100,000 population) (Figure 5.2).

Supplementary tables of emergency hospital admissions and rates by age group are shown at the end of this report.

Figure 5.1: Weekly number of community-acquired emergency influenza, RSV and COVID-19 hospital admissions, by epidemiological week

Figure 5.2: Weekly community-acquired emergency influenza, RSV and COVID-19 hospital admission rates per 100,000 population, by age group and epidemiological week

Community-acquired emergency inpatients for influenza, RSV and COVID-19 inpatients remained broadly stable, with a slight decline (Figure 5.3). Community-acquired emergency inpatients by age group for the previous year are shown in (Figure 5.4).

Figure 5.3: Influenza, RSV and COVID-19 community acquired emergency inpatients, by day

Figure 5.4: Influenza, RSV and COVID-19 community acquired emergency inpatients, by age group and day

6.1 Deaths related to influenza and/or pneumonia

NISRA death statistics are published weekly. These statistics report on deaths where influenza and/or pneumonia was mentioned anywhere on the death certificate. As a result, the counts will reflect deaths where influenza or pneumonia has contributed to a death but was not necessarily the underlying cause of the death.

The latest data is available for week ending 01 May 2026. In week 18, there were 47 influenza and/or pneumonia related deaths out of 332 deaths reported (14.2%). This is lower to the previous week (19.3%) (Figure 6.1).

Figure 6.1: Weekly deaths and percentage of registered deaths related to influenza and/or pneumonia, to most recent registration week

6.2 Deaths related to COVID-19

NISRA death statistics report on deaths where COVID-19 was mentioned anywhere on the death certificate. As a result, the counts will reflect deaths where COVID-19 has contributed to a death but was not necessarily the underlying cause of the death.

The latest data is available for the week ending 01 May 2026. In week 18, there were no COVID-19 related deaths among the 332 deaths reported. This is a slight decrease to the previous week when one COVID-19 death was reported (0.3%) (Figure 6.2).

Figure 6.2: Weekly deaths and percentage of registered deaths related to COVID-19, to most recent 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).

EuroMOMO is a European mortality monitoring activity, aiming to detect and measure excess deaths related to seasonal influenza, pandemics and other public health threats. During the current 2025/26 season, excess mortality has been reported in weeks 48 and 50, 2025, and week 03, 2026. Reports on excess deaths across Europe and the United Kingdom are published weekly.

9.1 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.

9.2 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 report offers the most up-to-date information available.

Rates per 100,000 population are calculated using the NISRA 2024 Mid-Year Population Estimates.

9.3 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 2022 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.

9.4 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 Northern Ireland 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.

9.5 Community surveillance

Care home outbreaks

PHA conducts surveillance of outbreaks across multiple settings, including care homes (nursing homes and residential homes) in Northern Ireland that are registered with the Regulation and Quality Improvement Agency (RQIA). All care homes have a requirement to notify the PHA Health Protection duty room of suspected outbreaks of any infectious disease. A confirmed outbreak of influenza, RSV or COVID-19 is defined as where there are two or more confirmed cases with onset within a 14 day period, where transmission within the care home facility is considered the likely cause.

9.6 Secondary care surveillance

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 to acute hospitals are estimated by combining data from the 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., 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. 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.

9.7 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.

9.8 Vaccine Effectiveness methodology

Study setting and population

This study was conducted including data from Scotland, Wales, and Northern Ireland. The study population included all individuals aged ≥2 years who had a hospital admission and a recorded influenza RT-PCR test during epidemiological weeks 40 to 47 of the 2025/26 season.

Data sources

Influenza testing

In Northern Ireland, influenza testing data were sourced from the regional influenza surveillance system, which collates virological reports from the Regional Virus Laboratory (RVL) and all local Health and Social Health (HSC) Trust laboratories. Influenza admissions were defined as admissions in which a positive influenza test was obtained up to 14 days before or within 48 hours following the date of hospital admission.

Scottish influenza laboratory testing data was derived from Electronic Communication of Surveillance in Scotland (ECOSS) dataset. For this analysis, ECOSS data was extracted 03 December 2025. The case definition for a positive influenza test were patients with a positive test 14 days before or within 48 hours of hospital admission. This was limited to emergency care admissions.

In Wales, influenza testing data were provided from the Public Health Wales national microbiology Datastore (a repository containing all PCR diagnostic data across NHS Wales Microbiology laboratories). Testing data were deduplicated to 28-day episodes, with sample date of earliest positive influenza test retained. Point of care testing data are not currently included, however national guidance in Wales encourages confirmation of influenza positive point of care tests through multiplex PCR methods (these test results are included).

Vaccination status

In Northern Ireland, vaccination status was obtained from the Northern Ireland Vaccine Management System (VMS) and defined at the time of specimen collection. Individuals were classified as vaccinated if they had received a seasonal influenza vaccine at least 14 days before their sample date. Those with no record of influenza vaccination prior to specimen collection were considered unvaccinated. Patients who tested positive for influenza within 14 days of vaccination, classified as partially vaccinated, were excluded from the main analysis to allow sufficient time for an adequate immune response to develop.

Vaccination status in Scotland was derived from the vaccination management tool (VMT) used to record influenza vaccination in those ≥ 2 years old. Vaccination status was determined at the time of specimen collection. Patients were considered vaccinated if they had received a dose of the seasonal influenza vaccine at least 14 days prior to their sample date. Those with no record of influenza vaccination before the sample date were considered unvaccinated. Patients who tested positive for influenza within 14 days of receiving the vaccine – considered partially vaccinated – were excluded from the main analysis, to allow for the time required for an adequate immune response to develop.

In Wales, vaccination statuses were obtained from the Welsh Immunisation System (WIS) and linked to admission and virological test data using patient NHS number. WIS contains vaccination status data for all Wales residents registered for NHS care, who are eligible for free influenza vaccination as part of the annual NHS programme. WIS includes vaccination data from both GPs and community pharmacies. Vaccination status was defined at the time of specimen collection. Individuals were classified as vaccinated if they had received a seasonal influenza vaccine at least 14 days before their sample date. Those with no record of influenza vaccination prior to specimen collection were considered unvaccinated. Patients who tested positive for influenza within 14 days of vaccination, classified as partially vaccinated, were excluded from the main analysis to allow sufficient time for an adequate immune response to develop.

Hospitalisation

Patients in Northern Ireland were classified as hospitalised if they had a hospital admission recorded in the Epic electronic health record system occurring between epidemiological weeks 40 and 47.

Scottish patients were considered hospitalised if they had a Rapid Preliminary Inpatient Data (RAPID) emergency admission recording taking place between epidemiological weeks 40 and 47.

In Wales, patients were classified as hospitalised if they had a recorded admission in ICNet with a linked virological test result occurring between epidemiological weeks 40 and 47

Exclusions

Patients who were partially vaccinated (i.e., received influenza vaccine <14 days before sample collection) were excluded from the main vaccine effectiveness analysis. Individuals with a positive SARS-CoV-2 test were excluded from the control group.

Covariates

Due to limitations in data availability for deprivation and at-risk status across nations, pooled estimates containing data from Scotland, Wales and Northern Ireland were adjusted for sex, epidemiological week and region.

Statistical methods

A binomial regression model was used to estimate odds ratios for influenza A positivity by vaccination status. To explore effect modification, we included an interaction term between vaccination status and region/age group.

Vaccine effectiveness (VE) was calculated as:

VE = (1 – adjusted odds ratio) x 100%

Due to the inability to ascertain eligibility status in at-risk populations ages 18-64 years, vaccine effectiveness in this eligible group is not yet available. Future analyses will explore other this and factors underlying vaccine effectiveness including product type and waning.

10.1 Unique episodes of influenza, RSV and COVID-19, by epidemiological week, over a six week period

10.2 Influenza, RSV and COVID-19 episode rates per 100,000 population, by age group, over a six week period

10.3 Influenza, RSV and COVID-19 episode rates per 100,000 population, by local government district, over a six week period

10.4 Total tests and positivity for influenza, RSV and COVID-19, by epidemiological week, over a six week period

10.5 Positivity for influenza, RSV and COVID-19, by age group and epidemiological week, over a six week period

10.6 Unique episodes of influenza, by subtype, over a six week period

10.7 Total sentinel tests and positivity for influenza, RSV and COVID-19, by epidemiological week, over a six week period

10.8 Total non-sentinel tests and positivity for influenza, RSV and COVID-19, by epidemiological week, over a six week period

10.9 Number of sequenced samples for variants in Northern Ireland

This table only shows counts for lineages with 10 or more sequenced samples from 2025 - 19 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.

10.10 Flu/ILI consultation rates per 100,000 population, by age group, over a six week period

10.11 Flu/ILI consultation rates per 100,000 population, by Health and Social Care Trust, over a six week period

10.12 ARI consultation rates per 100,000 population, by age group, over a six week period

10.13 ARI consultation rates per 100,000 population, by Health and Social Care Trust, over a six week period

10.14 COVID-19 consultation rates per 100,000 population, by age group, over a six week period

10.15 COVID-19 consultation rates per 100,000 population, by Health and Social Care Trust, over a six week period

10.16 Number of community-acquired emergency hospital admissions, over a six week period

10.17 Community-acquired emergency hospital admission rates per 100,000 population, by age group, over a six week period