By Professor Dominic Harrison, director of public health Blackburn with Darwen Council

THE government is expected to announce its proposals for international travel this week, setting out which countries will be green, amber or red listed from May 17.

The expectation is that ‘only essential travel’ will be allowed to red listed countries. Travellers would continue to require quarantine on return in a government-listed quarantine hotel, for which the traveller must pay.

Travellers to amber listed countries would require self-isolation at home on return to the UK. Those travelling to green-listed countries may be less restricted. Most countries and airlines may now require certification of vaccine status and a negative PCR test before any flight. Travellers in quarantine or self-isolation will also have to have a PCR test on day two and eight of their self-isolation.

If either test proves positive, the self-isolation date is re-set from the date of the positive test. These are likely to be the key measures - but the details outlined may change or be expanded with the final announcement.

We now know at least four things about the risks of international air travel.

Firstly we know that those who fly most, will be most at risk of travel related infections. Looking at international travel data for 2018 we can see that just one per cent of English residents are responsible for nearly a fifth of all flights abroad. Department of Transport data suggests that the 10 per cent of the most frequent fliers in England took more than half of all the international flights in 2018, but 48 per cent of the population of England did not fly abroad at all.

Secondly, we know that as the UK has recently had very low rates from ‘within country infections’, travel related cases have become more visible in the overall case numbers. By late April, despite widespread travel restrictions, travel related cases were 17 per cent of all cases identified in Blackburn with Darwen.

Thirdly, we know that travel related cases are more likely to have variants of the Covid-19 virus. Over the last two weeks, the UK has seen a sharp rise of travel related variant cases identified through genome testing – with India for instance now contributing three new variants to the international list.

Fourthly we know that some travel related cases, including those with variants, appear to show evidence that transmission was most likely on the return flight to the UK. We now have documented cases of travellers returning to the UK who were negative on a PCR test as they boarded the plane, negative on day two of self-isolation, but positive on the day eight PCR test. This indicates they were most likely to have been infected at the point of return to the UK - either in transport back to the airport, at the airport, or on the flight. Those most at risk on an airplane will be those in the same row or a row behind or in front of an infected person. The infected person is highly likely to asymptomatic. The longer the flight, the greater the risk of transmission.

It looks like we are all going to get a choice on the risks we are willing to take with air travel.

I will be taking my two week summer holiday in England this year.