Coronavirus (Covid-19) Infection Survey Northern Ireland – 14 August to 20 August 2021

Date published: 27 August 2021

The Department of Health today published the next in the series of weekly results from its COVID-19 Infection Survey (CIS).

covid latest stats

The findings set out in this report relate to modelled positivity estimates for NI for the week up to the 20 August 2021. 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 residences).

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 (14 August – 20 August), it is estimated that 43,300 people in Northern Ireland had COVID-19 (95% credible interval: 33,600 to 53,900). 
  • This equates to 2.36% of the population (95% credible interval: 1.83% to 2.94%) or around 1 in 40 people (95% credible interval 1 in 55 to 1 in 35).
  • Modelling suggests that the percentage of people testing positive has increased in the week ending 20 August in Northern Ireland.
  • In the latest six-week period, there were 14,562 swab tests taken in total from 10,681 participants. Of these, 193 participants tested positive from 148 different households.
  • In the latest two-week period, of the 5,160 participants in the study, 90 tested positive from 69 households.

Variant analysis

A new variant of the coronavirus (COVID-19) was identified in the UK in mid-November 2020. The Alpha variant (B.1.1.7, previously known as the UK variant) of COVID-19 has changes in one of the three genes that COVID-19 swab tests detect, known as the S-gene. This means in cases compatible with the Alpha variant, the S-gene is not detected by the current test and has the pattern ORF1ab+N (S gene negative) in the main variant analysis. Other variants – including both Delta (B.1.617.2) and Beta (B.1.351) – are positive on all three genes, with the pattern ORF1ab+S+N. Almost all ORF1ab+S+N cases in the UK will now be the Delta variant, so this group is labelled “Compatible with the Delta variant”.

More information on individual variants and where they were first detected is available on the government variant dashboard.

In recent weeks, infections compatible with the Delta variant have been the most common across all four UK countries. Due to this high proportion of a single variant, a breakdown of infections by variant has not been included.  The main variant analysis was last published on the 23 July 2021, where more details can be found. Infections by variant will continue to be monitored and the charts and analysis will be introduced when considered helpful.

ONS has published a blog where more can be read about COVID-19 variants.

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.
  1. 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.
  1. 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 institutional settings.
  1. 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.
  1. 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.
  1. Further information about quality and methodology associated with the survey can be found on the ONS website.
  1. This publication is available on the Department's website.
  1. Additional information is available from:
    Information Analysis Directorate
    Department of Health
    Annex 2, Castle Buildings
    Belfast BT4 3SQ
    Telephone:  028 9052 2340         E-mail:
  2. For media enquiries please contact the DoH Press Office by email
  3. Follow us on Twitter @healthdpt.
  4. 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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