Coronavirus (Covid-19) Infection Survey, Northern Ireland: Weekly Report

The Department of Health today published the next in the series of weekly results from its COVID-19 Infection Survey (CIS). The findings set out in this report relate to modelled positivity estimates for NI for the week up to the 19 March 2022. The aims of the CIS are to estimate how many people have the infection and the number of new cases that occur over a given time as well as estimating how many people have developed antibodies to COVID-19.

The survey over time will help track the extent of infection and transmission of COVID-19 among people in the community population (those in private residential households).

Key Findings

Due to the relatively small number of tests and positive swab results within our sample, credible intervals are wide and therefore results should be interpreted with caution.

• during the most recent week of the study (13 March – 19 March 2022), it is estimated that 108,700 people in Northern Ireland had COVID-19 (95% credible interval: 92,500 to 126,000).
• this equates to 5.92% of the population (95% credible interval: 5.04% to 6.87%) or around 1 in 17 people (95% credible interval: 1 in 20 to 1 in 15).
• modelling suggests the percentage of people testing positive decreased in the week ending 19 March 2022 in Northern Ireland.
• in the latest six-week period, there were 16,398 swab tests taken in total from 11,872 participants. Of these, 976 participants tested positive from 742 different households.
• in the latest two-week period, of the 5,375 participants in the study, 313 tested positive from 248 households.
• the percentage of people testing positive increased in adults aged over 60 years in the most recent week. The percentage of school aged children testing positive decreased, whilst the trend was uncertain in young adults.
• in the most recent week, the percentage of people with infections compatible with the Omicron BA.2 variant increased in England, Wales and Scotland and decreased in Northern Ireland (see below for more information on the variant analysis undertaken).

Variant analysis

The World Health Organization (WHO) have defined names for Variants of Concern. These are variants that the UK government has under surveillance. You can find out more in the latest SARS-CoV-2 variants of concern and variants under investigation in England briefing document.

Currently circulating variants of concern in the UK are:

• delta: B.1.617.2 and its genetic descendants
• omicron: B.1.1.529 (which includes sublineages BA.1, BA.1.1, BA.2 and BA.3)

The Omicron variant BA.1 has changes in one of the three genes that the coronavirus swab used in the survey tests detects, known as the S-gene. This means the S-gene is no longer detected by the current test. When there is a high viral load (for example, when a person is most infectious), not detecting the S-gene in combination with detecting the other two genes (ORF1ab and N-genes) is a reliable indicator of this Omicron BA.1 variant. However, as the viral load decreases (for example, if someone is near the end of their recovery from the infection), not detecting the S-gene is a less reliable indicator of this Omicron variant.

The Omicron variant BA.2 does not have changes in the S gene, and therefore all three genes, or the S-gene and either ORF1ab or N, will usually be detected in infections with this variant. Delta also does not have changes in the S-gene, and therefore the same sets of genes will usually be detected with the Delta and Omicron BA.2 variants. The genome sequencing analysis shows that almost all infections where the S-gene is detected are now the Omicron BA.2 variant. For this reason, we now label cases with gene patterns ORF1ab + N + S, ORF1ab + S and N + S as “compatible with the Omicron BA.2 variant” in our main variant analysis. The Omicron BA.2 variant is now the most common variant in England, Wales, Northern Ireland and Scotland. 

More information on how variants from positive tests on the survey are measured can be found in the ONS Understanding COVID-19 Variants blog and in the methodology article.

Notes to editors: 

1. The Department of Health has been working along with the Public Health Agency, Northern Ireland Statistics and Research Agency and the Office for National Statistics (and its various survey partners) to extend the COVID-19 Infection Survey to Northern Ireland. Fieldwork in Northern Ireland began on 27 July 2020.
2. All results are provisional and subject to revision. Due to relatively small number of tests and positive swab tests within the sample, credible intervals are wide and therefore results should be interpreted with caution.
3. These statistics refer to infections reported in the community (i.e. private households). These figures exclude infections reported in hospitals, care homes and/or other communal establishments.
4. Estimates of the total national proportion of the population testing positive for COVID-19 are adjusted to be representative of the population of Northern Ireland that live in private residential households in terms of age, sex and region.
5. Weekly reports are to be published with findings from the COVID-19 Infection survey. It is anticipated that new and further analyses will be added to the weekly reports over time.
6. Further information about quality and methodology associated with the survey can be found on the ONS website.
7. This publication is available online at:
8. Additional information is available from:
   Information Analysis Directorate
   Department of Health
   Annex 2, Castle Buildings
   Stormont
   Belfast BT4 3SQ
   Telephone:          028 9052 2340         E-mail: statistics@health-ni.gov.uk
9. For media enquiries please contact the DoH Press Office by email pressoffice@health-ni.gov.uk.
10. Follow us on Twitter @healthdpt
11. The Executive Information Service operates an out of hours service For Media Enquiries Only between 1800hrs and 0800hrs Monday to Friday and at weekends and public holidays. The duty press officer can be contacted on 028 9037 8110.

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