Covid-19 cases have declined significantly in the last month, after the BA.2 offshoot of the Omicron variant caused them to peak again in March.

Hospitalisations and deaths have also been falling consistently. However, the virus has not gone away.

Experts have suggested it won’t be long before we are talking about “catching a Covid” just as we do with a cold.

This means the virus is set to remain part of our lives for the foreseeable future, and it is therefore important to recognise the signs of it, and be aware of when you might have it.

The best way to do this is by testing yourself.

The Government has ended the provision of free Covid tests, but lateral flows can be bought for around £2 from pharmacies.

Here’s what you need to know about how accurate they are, and whether you can test negative even when you have the virus.

A study published in the Clinical Epidemiology journal in October 2021, conducted by researchers from the University College London, Liverpool University, Harvard University and the University of Bath, found that lateral flow tests are more than 80 per cent effective at identifying positive Covid-19 cases.

And the study found the tests are more than 90 per cent effective at detecting the virus when someone is at their most infectious.

However, as they are not 100 per cent accurate it is technically possible to test negative while having the virus.

The Medicines and Healthcare products Regulatory Agency (MHRA) has stated “no test is 100 per cent reliable” because lateral flow tests cannot always detect low levels of the virus.

The NHS says: “A negative result means it’s likely that you are not infectious. But a negative test is not a guarantee you do not have Covid-19 and there’s still a chance you may be infectious. You should follow advice on how to avoid catching and spreading the virus.”

UK-based GP Dr Gary Bartlett told The Independent: “What I often tell my patients is that lateral flow tests are really useful for asymptomatic screening (testing when you have no symptoms).

“If you have symptoms suggestive of Covid then you must get a PCR test which are the gold standard test for Covid as they are better at detecting Covid. If you have Covid symptoms, lateral flows are less reliable as they can be associated with false negatives, often leading the person to believe that they don’t have Covid when in fact they do.”

He added that false positives – a test showing you have Covid when in fact you do not =- are extremely rare, and only happen in “a fraction of a per cent of occasions”.

Professor Adam Finn, a member of the UK’s Joint Committee on Vaccination and Immunisation (JCVI) told the British Medical Journal: “If [lateral flow tests] come up positive that means you are potentially infectious to others and must self-isolate. They are not ‘green light’ tests: you cannot be sure that if the test is negative you are not infectious, and you must continue to take the usual precautions.”

To take an antigen test, you take a swab from inside your nostril, the back of your throat, or both, depending on the specific test you are using.

You then mix that swab with solution and drip it onto a device which contains a test strip.

The test strip has antibodies specific to the Covid-19 virus painted on it in a thin line.

These antibodies will bind to any antigen in the sample. If the testing strip detects the virus, it will show up as a thin red line next to the T on the device.

The NHS now lists the following as official Covid symptoms:

The NHS says the symptoms “are very similar to symptoms of other illnesses, such as colds and flu”.

If you have Covid-19 symptoms you are no longer legally required to self-isolate.

However, the NHS advises anyone with symptoms to stay at home and avoid contact with others.

If you test positive or experience symptoms, the NHS advises taking the following steps:

If you live in Scotland, Wales or Northern Ireland, the advice is as follows:

If you test positive for Covid-19 you should self-isolate for five full days. Day one is the day after your symptoms started or the day after you had the test if you do not have symptoms (whichever is earlier).

You should then take a lateral flow test on day five. If it is negative and you don’t have a high temperature you can leave self-isolation on day six.

However, if you still have a temperature and feel unwell you should continue to self-isolate until your temperature returns to normal or you feel better.

If the day five or day six test is positive you should continue taking daily lateral flow tests until you get two negative tests in a row, taken a day apart or until day 10 – whichever is sooner.

All rights reserved. © 2021 Associated Newspapers Limited.