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Positivity metrics for some respiratory viruses not updated this week

Due to a data issue with Respiratory Data Mart, positivity metrics for Influenza, RSV, hMPV, Parainfluenza and Rhinovirus will not be updated this week.

BackEntry title:

COVID-19 cases compared with previous 7 days

Last updated on Wednesday, 12 February 2025 at 10:32am

Summary

Topic
COVID-19
Category
headline
API name
COVID-19_headline_cases_7DayChange

Rationale

The timely identification of cases is important to controlling the spread of COVID-19 and reducing the burden on healthcare systems.

Definition

This metric shows the difference in the number of reported new cases in the last 7 days compared to the previous 7 days. New cases are reported by specimen date - the date the first sample that identified the infection was taken from an individual.

Methodology

COVID-19 cases are identified by taking specimens from people and testing them for the SARS-CoV-2 virus. If the test is positive, this is a case. Historically, cases identified using 2 types of tests for the SARS-CoV-2 virus are reported on the dashboard:

  • polymerase chain reaction (PCR) tests, which require processing in a laboratory
  • rapid lateral flow virus (LFD) tests, which are swab tests that give results in less than an hour, without needing to go to a laboratory (changes to this testing scheme are highlighted below)

Up until the end of March 2022, all lateral flow tests reported via the “Report a COVID-19 rapid lateral flow test result” GOV.UK service were included. The service could not be used to report results from test kits that were paid for, and therefore results from paid for test kits were not included in figures on the dashboard. This service ceased on 31 March 2022, with the introducing of the Living with COVID-19 strategy, where the provision of free universal testing was limited to symptomatic at-risk groups and social care staff.

From 1 April 2024, there were further changes to LFD testing where the free provision of LFDs for the management of outbreaks in high risk settings ended.

Historically, some positive rapid lateral flow test results are confirmed with lab-based PCR tests taken within 72 hours however, given the changes described above, this is no longer applicable. If the PCR test results are negative, these are not reported as confirmed cases.

People who test positive again after a given time period are counted as new cases. In England people are counted as new cases if they test positive again more than 90 days after their last positive test.

Data for the last 5 days by specimen date are considered incomplete as it takes time to get test results and record them on relevant lab systems. Currently, cases data for England includes all positive lab-confirmed PCR test results.

The change in reported new cases is calculated as the difference between the total of the daily cases counts in the 7 days up to and including the most recent date with "complete" data (that is, 5 days before the current date) and the total of the daily cases counts in the previous 7 days.

Caveats

This figure will underestimate the actual number of COVID-19 infections due to people not testing or not being able to report rapid lateral flow test results.

The change includes newly-reported cases, and adjustments to previously-reported cases – these may go up or down.

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