All non-essential international travel from the UK is currently illegal, but that may change from 17 May. And when it does, the traveller is likely to face repeated demands for evidence of negative tests for Covid-19.
These are the key questions and answers.
What’s the background?
Many countries now demand negative Covid-19 test results from incoming travellers.
We know relatively little about the opening up of international travel from the UK – but we do know that on return there will be a need to test both pre-departure and post-arrival.
There is no clarity yet about what sorts of tests are needed.
This reflects the global lack of agreement on the type of test and the timing requirements.
What tests are there?
Covid tests look either for the presence of the virus in the body right now – or evidence of a previous response to it by your immune system.
Those that look for current infection are broadly known as diagnostic tests. They can be molecular, such as PCR tests, which look for the virus’s genetic material; or antigen tests that detect specific proteins from the virus, usually the so-called “spike” protein.
Molecular tests are certainly preferred; the World Health Organisation says negative antigen diagnostic test results “should not remove a contact from quarantine requirements”.
An antibody test looks for antibodies created by your immune system in response to a virus. They can take several days or weeks to develop after you have an infection, and stay in your blood after you recovery. It is believed that the presence of antibodies can provide some immunity to Covid-19 in future.
How are tests rated?
Tests are never 100 per cent accurate, and vary in their “sensitivity” and “specificity”. Sensitivity means the proportion of carriers of the virus who are correctly identified; specificity refers to the proportion of non-carriers who are correctly identified. So 100 per cent sensitivity would mean no false negatives, while 100 per cent specificity means no false positives.
Which is the best?
The most popular among governments stipulating a particular test for travellers is the PCR (polymerase chain reaction) version. This is also the standard NHS test and has been described as the “gold standard”.
A swab is used for the back of the throat and/or the top of the nostrils. The sample is then processed to try to detect genetic material in the virus called RNA, which is evidence of the presence of Covid-19.
In a specialist laboratory, a solution known as a reagent is added to the sample. The resulting substance is then cooked: subjected to a series of alternating temperature steps using a “thermal cycler”, to create billions of copies of the RNA. This makes them detectable.
The analysis typically takes 12 hours. Since samples must be transported to the lab and are typically processed in bulk, getting a result can take much longer.
Are swab tests uncomfortable?
They are. Many people find the swab procedure unpleasant: a throat swab can make you want to gag, while a nasal swab feels intrusive and even threatening. But health professionals are trained to target material that may contain RNA.
Self-testing kits are available – but there is concern that untrained individuals or their partners may not properly carry out the test. Some providers will arrange for a medical professional to talk you through the test on a video call.
What about lateral flow tests?
These antigen tests, using lateral flow devices (LFDs) are at the heart of the British government’s “moonshot” plan for widespread mass testing. These rapid antigen tests are cheap and quick, and do not require any “cooking”.
They generally require swabs.
“Getting into the habit of regular testing as part of our everyday lives will play an important role as restrictions are cautiously lifted and we begin to get back to more normal ways of life,” says the government.
It is expanding from school and workplace testing to offer them free to everyone for twice-weekly testing.
The government says: “We know that between one in four and one in three people who have Covid-19 never show any symptoms but that does not mean they are not infectious. Using LFDs enables us to rapidly identify people in the population who are asymptomatic, with results produced in 30 minutes.
“We also know that lateral flow devices are effective at finding people with high viral loads who are most infectious and most likely to transmit the virus to others.
“We’ve also looked very carefully at the evidence that’s emerging from LFD tests that have been delivered at home and in testing sites over recent weeks, and real life scenarios suggests they are 99.9 per cent accurate which means that the risk of false positives is extremely low – about one in 1,000 – which is a very good test.”
But the British Medical Journal cautions: “Their performance as a ‘test to enable’ is lacking.”
It reports: “Testing by Boots test centre employees (following written instructions) achieved sensitivity of just 58 per cent.” In other words, two out of five subjects who were infected were not picked up by the tests.
Is ‘lateral flow’ the same as ‘rapid antigen’?
All lateral flow tests are rapid antigen tests. Indeed, the UK government calls the system ”rapid lateral flow antigen testing”.
“Lamp” (loop-mediated isothermal amplification) diagnostic tests are molecular. They use similar swabs, or simply (and more comfortably) a saliva sample, and do not require that expensive and time-devouring thermal cycler.
They can be processed on site – for example at Heathrow airport, where Collinson offers the technique for its testing centres in Terminals 2 and 5.
In a wide-scale experiment carried out at NHS trusts and universities, Lamp tests had a sensitivity of 79 per cent and a specificity of 100 per cent – when compared with the PCR results for the same people. In other words, there were no false positives (which is good news for uninfected people) but one in five false negatives (bad news for countries wishing to keep out carriers of the virus), relative to the PCR result.
But the government reported: “In samples with a higher viral load, the sensitivity of the test increased to 94 per cent for saliva and 100 per cent for swabs.”
There are also Transcription-Mediated Amplification (TMA) tests, another molecular variant, similar to the Lamp test. It is molecular, and still needs the sample to be heat-treated to replicate any RNA but is swifter, simpler and cheaper. They have been accepted by countries such as Spain, but are not generally available in the UK.
So what do I need to travel?
That all depends on the country you are visiting – as well as your nationality and/or departure point.
The standard is a PCR test conducted within 72 hours of arrival at your destination.
That can prove a challenge if you have a long flight and/or you are planning to travel during or immediately after a weekend/public holiday.
Other nations have their own time limits. Some insist on 48 hours while others allow four, five or even seven days before departure.
But the European Commission has published a list of acceptable rapid antigen tests that includes lateral flow tests.
These are cheaper and faster and can increasingly be taken at the airport before departure. It may well be that they become the common standard for EU countries.
Do need to self-isolate between taking the test and departure?
No, though of course the less you venture out the lower the chance you will be infected.
Can I get a free test through the NHS?
No. Tests provided free for the public who are concerned that they may be infected or are testing routinely must not be used for the purposes of travel. Conversely, if you fear you may have contracted coronavirus, you should seek an NHS test rather than one that is offered to travellers – who are presumed to be negative.
So how do I find one?
If family or friends can recommend a contact, then go for that. You could ask a long-established travel health provider, such as the Fleet Street Clinic in central London, Nomad (with locations in London, Bristol, Cardiff and Manchester) and Masta (which has a presence in dozens of pharmacies).
An established, doctor-led practice is likely to be both more professional and more expensive than a new venture that is leading on price. They use the highest grade of medical test available with the best possible accuracy ratings.
Increasingly airports are offering tests with (in some cases) discounts for ticketed passengers.
Will I need a test on arrival?
Quite possibly. Many countries stipulate one or more tests on arrival, usually at the traveller’s expense.
Returning to the UK currently requires a test before departure and two more on arrival, on days two and eight.
From 17 May, when the “traffic light” system may or may not begin, people coming to the UK even from low-risk “green” countries will require testing post-arrival.
How much will that cost me?
The price depends on the kind of test. PCR is always the most expensive, typically £100-£150 – though if you need an instant turn-round it could be £500.
Lateral flow tests are cheaper and, when widespread testing begins, should be available for £20-£30.
There are concerns among travel industry bosses that high prices could mean that only richer people can afford to travel.
Julia Lo Bue-Said, chief executive of Advantage Travel Partnerships, said: “Aligning travel to ‘green’ countries under the government’s proposed traffic light system will require affordable, easily accessible testing.”
John Holland-Kaye of Heathrow airport said: “The main concern is the cost of all of this – both the pre-departure test and the post-arrival test which, as I understand it, needs to be a PCR test.
“This could become prohibitively expensive for a lot of people who just want to be able to go about their normal business.
“We need to make sure that this doesn’t just become something that only wealthy people can afford to do, that it’s much more democratic and accessible than that.”
Prices for tests are likely to come down. UK prices are high by global standards: in Mumbai, for example, the highest price for a PCR test is 600 rupees (£6) with some airlines offering tests for half that.