Provisional figures from Public Health Mid West show there were a further 71 cases of Covid-19 infection in Limerick over the weekend, with 31 on Saturday and 40 on Sunday.
More than 250 new Covid-19 cases were recorded in Limerick since Sunday, 16 May.
The department is "investigating more than 20 school situations and more than 20 workplace situations" in the mid-west, it said, most of which are in Limerick city and county.
HSE Mid West Director of Public Health Dr Mai Mannix said from the examination of those infected and their close contacts, the surge in figures is coming mainly from indoor family gatherings, birthday parties, end of school gatherings and Eid celebrations.
She said Covid hospital in-patients at University Hospital Limerick also rose from two to 14 over the past week, which is a worrying trend, particularly as it's young parents aged in their 40s who are ending up sick in hospital.
Dr Mannix urged the public to continue observing the public health guidelines, and to avoid indoor gatherings.
She believes people are dropping their guard as more and more people are getting vaccinated and there is a move towards easing more restrictions.
The HSE is urging people in Limerick to avail of a free walk-in and drive-through Covid-19 testing clinic at St Joseph's Health Campus, Mulgrave Street which opens this Wednesday morning for five days. No appointment is needed.
Dr Mannix asked anyone who thinks they may have the virus to get tested, particularly at this sensitive time when Leaving Cert students are getting ready to sit their exams, and it was important that they be Covid free to do their exams.
The four-bay facility will operate from 11am to 7pm, from Wednesday 26 May to Sunday, 30 May.
"The service is for those who have Covid-19 symptoms and for people who are concerned that they may have been exposed to Covid infection in the past two weeks. Children can get tested if they are accompanied by a parent or guardian," said a statement from Public Health Mid-West.
Dr Mannix said young people are being admitted to hospital.
"Our health service is under enormous pressure as a result of the cyber attack on our IT systems, which is furthermore being compounded by the increase of young people being admitted to University Hospital Limerick.
"The past two weeks have shown just how quickly this disease spreads into multiple settings when we drop our guards. But if we act now, remain vigilant, and avail of testing, we can prevent the start of a potentially large community outbreak in Limerick."
HSE Mid West Community Healthcare Chief Officer, Maria Bridgeman said: "While the vaccination programme has been a success to date, it is still the case that the majority of people remain unprotected against the risks associated with Covid-19. Therefore, it is vital that everyone continues to follow all public health guidance to prevent a further spread of this virus in our community. I am urging everyone, particularly the people of Limerick, to avail of this testing service."
Colette Cowan, CEO of UL Hospitals Group, said there has been an increase in Covid-related activity in the hospitals in recent days, and "there are currently 12 Covid-positive inpatients in UHL".
"This includes a small number of relatively young people so unwell that they have required critical care. The easing of restrictions across society and the progress of our vaccination gives us great cause for hope but the increase in hospitalisations in recent days underscores the continuing need for vigilance.
"This is particularly so when our hospitals continue to experience severe disruption in the wake of the cyber attack and when scheduled care has been greatly reduced to allow staff to care for the most seriously unwell and injured."