Infection Surveys and Symptom Panels

The ONS survey and the ZOE app use different methods.

How many people have a SARS-CoV-2 infection? During this pandemic, there is a vital interest in tracking infections over time.

This article looks at differences between infection surveys and the ZOE symptom study.

Tracking the pandemic

In the news, we often hear the daily number of new cases.

A case is a new person with a positive test result. That result can be via a laboratory or a lateral flow device.

Confirmed cases are not all cases. Testing regimes and accuracy influences these statistics. If testing availability changes, then recorded case numbers can increase or decrease. No country tests everyone: public health agencies will miss some cases.

There are also reporting lags. The daily reported number can reflect time taken to process results in labs. The types of tests are changing: with figures including lateral flow device tests.

This is the number of confirmed cases by date of report. (Image: Public Health England)

The Office for National Statistics infection survey

We need to understand how many people would test positive, if given a test. To that end, the Office for National Statistics conducts an infection survey.