Ireland is beginning to reimport Covid-19 cases through international travel, a senior health adviser has warned.
After the reproductive rate of Covid-19 in Ireland increased to one, Professor Philip Nolan, chairman of the National Public Health Emergency Team's (NPHET) modelling group, said a travel-related introduction of the disease is "problematic".
The Department of Health announced on Thursday that a further six people diagnosed with Covid-19 in Ireland have died.
It brings the total number of deaths linked to the virus to 1,743.
A further 23 cases of the virus have also been confirmed, bringing the overall number to 25,565.
It emerged that of the 23 new cases, 15 were "directly or indirectly" related to travel.
Prof Nolan told RTÉ Morning Ireland: "NPHET has recommended an escalation of a set measures to ensure that we close down on that.
"Our current tracking and tracing mechanism is how to track down those cases and isolate them at an early stage.
"We're also beginning to see people being more sociable, perhaps people being forgetful about the risks of the viral transmission, and we're seeing clusters of cases emerging in very small numbers of circumstances.
"These circumstances are those we advise against - gatherings of large numbers of people, particularly indoors, are the ideal opportunity for this fire to spread."
Prof Nolan said the advice from NPHET and from Government is to avoid any unnecessary international travel.
He added: "One can understand the Government's position, of course, that one always have to be proportionate in the level of restriction or the level of closure that would apply.
"That's perfectly reasonable for Government, and what many governments across Europe are doing is to tell you: 'Right now, we're recommending you can't travel.'
"But as we go on in the coming weeks, are there ways in which we can safely travel internationally, and there may well be.
"You could imagine the circumstances under which travel between two countries with low prevalence of the disease may well be feasible.
"The positions are not mutually exclusive."
The Irish Government has extended its advice for people to avoid all non-essential travel until July 20.
It is expected the Government will then publish a "green list" of countries which people can travel to.