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Information
21 November 2024: COVID-19 positivity metrics not updated

A technical issue has prevented UKHSA from updating COVID-19 positivity. Work is underway to resolve the issue and resume reporting as soon as possible. The data presented was last updated on 7 November 2024.

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Measles cases by week of symptom onset

Last updated on Tuesday, 3 September 2024 at 09:25am

Summary

Topic
Measles
Category
cases
API name
measles_cases_casesByOnsetWeek

Rationale

The timely presentation of measles cases by date of onset of rash (or symptoms), to display trends and monitor the course of the outbreak.

Definition

This metric shows the number of weekly laboratory confirmed cases of measles, reported to UKHSA, by date of onset of rash (or symptoms), age group, and UKHSA Region from 1 October 2023 onwards.

Methodology

Measles cases are identified by collecting appropriate samples from individuals presenting to a health professional with compatible symptoms.

Measles is a notifiable infection and therefore when a health professional suspects an individual may have measles they will report the case to a UKHSA Health Protection Team (HPT).

The Health Protection Team will send an Oral Fluid Kit (OFK) to all suspected measles cases for self-swabbing. This is done for surveillance purposes. In parallel, some cases will also be swabbed by health professionals for diagnostic purposes. Cases are identified using 2 types of tests for the measles virus:

  • Polymerase chain reaction (PCR) tests, which require processing in a laboratory, these can be tested in both NHS local and regional laboratories and at the Virus Reference Department (VRD) at UKHSA
  • IgM Serology testing at the VRD.

All positive cases identified at the VRD are reported to the UKHSA Laboratory Information Management System (LIMS) system, MOLIS. If the test results are negative, these are not reported as confirmed cases.

All local positive measles PCR tests are reported by local and Regional laboratories to UKSHA via the Second Generation Surveillance System (SGSS).

Case data for England includes all positive laboratory confirmed [GH1] PCR and IgM test results. In addition, laboratory confirmed cases captured through the UKHSA HPT case management system (HPZone) which have not yet had their positive result reported through the SGSS or LIMS systems are included (these are followed up to ensure the laboratory reporting route is as complete as possible).

Date of symptom onset is obtained by Health Protection Practitioners during follow up of suspected cases and entered on HPZone.

Case numbers are extracted on the Monday of each week and include data up to the Sunday of the previous week.

Data for the last 28 days by date of symptom onset are considered incomplete as it takes time for testing to be undertaken and for results to be available and flow via relevant laboratory reporting systems.

Caveats

Data are provisional and subject to change as more cases undergo confirmatory testing. Some locally tested cases are subsequently discarded through collection of further epidemiological information or after undergoing confirmatory testing at the reference laboratory.

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