Stormont's reaction to a "dangerous" new coronavirus variant discovered in the UK for the first time will ultimately decide whether the new variant makes its way to Northern Ireland, a public health expert has warned.
There is concern the Manaus strain may spread more rapidly and respond less well to existing vaccines.
Dr Gabriel Scally was speaking after Public Health England (PHE) confirmed six cases of the P.1 variant first detected in the Brazilian city of Manaus have been confirmed in Britain - three in England and three in Scotland.
Two were confirmed in South Gloucestershire but the third English case has not been located and could be anywhere, as PHE says the person did not complete their test registration card so their contact details are unavailable.
The Scottish Government said three residents who returned to north-east Scotland from Brazil, via Paris and London, subsequently tested positive.
Dr Scally said the new strain could lead to the pandemic taking hold again and causing more severe illnesses if it is allowed to spread unchecked.
However, he said that if the UK Government and Stormont Assembly implement travel restrictions and a proper quarantine system and the public continue to follow public health advice there was no reason to panic.
Dr Scally said the Assembly's reaction would decide whether the Manaus variant crosses the Irish Sea. The Belfast-born doctor, who is a member of the independent Sage committee, said it was a "worrying" development as the variant was one of those causing the greatest concern at present due to its impact on vaccines.
"It's a warning to us about how dangerous it is to leave borders open and not to have quarantine in place and catch all of these cases," Dr Scally said.
"It's a dangerous variant and Manaus was hit extraordinarily hard in the first wave and this new variant has hit it again, including infecting people who had already been infected. It means the virus manages to dodge some of the antibodies that have arisen from the first infection."
Dr Scally noted that the Republic of Ireland had a sizeable Brazilian population and said the Assembly would have to work with the UK and Irish Governments to stop the new variant from spreading.
"For a lot of international flights that is how people get to Northern Ireland, via Dublin airport," he said.
The epidemiologist said it was "almost inevitable" new strains would spread in the UK and Ireland due to open borders.
"The UK Government and the Irish Government have not got a good record on keeping variants out and they tend to shut the door after the horse has bolted, in this case they should shut the door now to make sure the variants don't get in," he said.
Dr Scally said without action the new variant could prolong the pandemic and "make it yet again more serious in terms of the severity of the illness". He said that while the number of cases was falling, "there is still a lot of transmission going on". "We really need to do three things - get the numbers down, keep them down and we need to keep it out by reducing the opportunity of importing new cases," Dr Scally said.