Coronavirus: How does the NHS test-and-trace system and app work?

The NHS Covid-19 app is being tweaked so that fewer people are "pinged" if they have been in contact with someone who has tested positive.

A record 690,000 people in England and Wales received an alert in the week to 21 July, because of a surge in Covid infections.

Until now, when someone tested positive but had no symptoms, the NHS Covid app went back five days before the test, and alerted any close contacts during that time.

From now on, the app will only alert close contacts from the previous two days before the positive test.

The sensitivity of the app itself has not changed, and anyone testing positive will still have to self-isolate.

People in England and Wales can download the NHS Covid app.

If you spend enough time close to another person using it, you will receive a "ping" alert if they later test positive for Covid. You need to be within 2m (6ft) of them for 15 minutes to trigger the alert.

Northern Ireland and Scotland have separate apps.

If you are "pinged" you're advised - but not legally obliged - to self-isolate for 10 days.

Government ministers have said it is "crucial" that people self-isolate when sent an alert.

However, it's feared that the large number of people being alerted has led to many users deleting the app, rather than face a period of self-isolation.

In England, employers providing critical services can now request an exemption for named employees who are fully vaccinated. Sectors include energy and emergency services.

Supermarket depot workers and food manufacturers are exempt from quarantine rules whatever their vaccination status.

A similar system is being launched in Scotland.

Some industries - including supermarkets and petrol stations - have struggled with staff shortages due to the high number of employees self-isolating.

When people test positive for coronavirus, they are asked to provide details of close contacts.

These include:

These contacts are then approached by text, email or phone

If you are contacted in this way, you must self-isolate at home for 10 days from your last point of contact with the person.

Refusing to do so is illegal in England, with fines starting at £1,000.

Other people in your household don't have to self-isolate unless you or they develop symptoms.

From 16 August, people who've had both jabs in England will no longer have to self-isolate after close contact with someone who tests positive.

From the same date, under-18s also won't have to isolate after contact with a positive case - to prevent entire classes or year groups having to self-isolate.

If contacted by NHS Test and Trace they will be advised to take one PCR test as soon as possible. As long as that is negative, and they don't develop symptoms, they won't need to take further action.

Similar changes are due in Scotland on 9 August. Wales will do the same on 7 August, although the rule for under-18s is not yet confirmed. Ministers in Northern Ireland are expected to discuss changes on 12 August.

Anyone who tests positive or develops symptoms will still need to self-isolate, regardless of vaccination status or age.

Each UK nation has its own contact-tracing service, but the rules are similar:

A £500 grant is available in England to people on low incomes who have to self-isolate. This includes parents who can't work because their child has to self-isolate. However, many applications have been turned down.

In Scotland people can apply for the Self-Isolation Support Grant, worth £500, and there is a similar scheme in Wales. In Northern Ireland a discretionary payment is available.

You may also be entitled to Statutory Sick Pay, which is worth £96.35 a week, or more if your employer has a sick pay scheme.