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. Some positive rapid lateral flow test results are confirmed with lab-based polymerase chain reaction (PCR) tests taken within 72 hours. 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. Cases data for England includes all positive lab-confirmed PCR test results plus, positive rapid lateral flow tests unless followed by a negative PCR test taken within 72 hours.
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 (i.e. 5 days before the current date) and the total of the daily cases counts in the previous 7 days.