The Health Service Executive has said up to 200 households are included in an outbreak of Covid-19 in Galway city, with cases mainly linked to interactions between young adults.
A total of 427 cases were confirmed among 18 to 24-year-olds in the two weeks to last Saturday, 27 February.
This followed a surge in the number of students at NUI Galway and GMIT testing positive for the virus.
The "significant outbreak" among young adults is said to have evolved over the last three weeks and is still ongoing.
The HSE West's Director of Public Health has urged students to avoid house parties and inter-household mixing.
Dr Breda Smyth said the B117 variant of the virus, first detected in the UK, increased transmissibility by 70%.
Rates in household contacts have increased from around 20% to almost 33% as a result.
Any student experiencing Covid-19 symptoms is urged to self-isolate immediately and call their GP to arrange a test.
The most recently available figures showing the 14-day incidence of Covid-19 per 100,000 people in Galway city shows a huge variation across three Local Electoral Areas.
While it stands at 177 per 100,000 people in the Galway City West area, the figure soars to 1,292 per 100,000 people in the City Centre, with 579 cases per 100,000 in Galway City East.