The HSE has confirmed that a single outbreak of Covid-19 among students in the west of the country has led to more than 442 further cases in more than 200 separate household outbreaks.

Speaking at this evening's Department of Health briefing on Covid-19, HSE West Public Health Director Dr Breda Smyth outlined the details of how the virus spread.

Dr Smyth said the initial outbreak was "quite large", and involved young adults aged between 16 and 24.

Up to the end of yesterday, a total of 442 cases could be linked back to that single outbreak.

Of those 442 cases, 179 were linked to multiple household clusters, where there were multiple households involved.

Of these, there were 20 clusters in total, ranging from two to 42 cases each.

In addition, Dr Smyth said, there were 145 cases linked to single household outbreaks, as well as another 118 cases confirmed.

In total, 224 households were affected from the initial outbreak.

Dr Smyth said that in addition to spreading infection in the community, there were knock-on effects in other areas, such as exposure to the virus, as well as transmission, in the hospitality and retail sectors.

She told this evening’s briefing that a further cluster of infection was recorded in another part of the country, which was linked to the initial outbreak.

She said the movement of the young people through the region as a result of socialisation was among the primary reasons for transmission, adding that house parties were also a factor.

Dr Smyth also detailed the timeframe for how the virus spread from the first outbreak.

On Day One of the outbreak, there were two clusters, four households and four cases confirmed. On Day Two, this became six clusters, 12 households and 15 cases.

By the end of Week One, there were 16 clusters, 48 households and 85 cases confirmed. By Day 21, or Week Three, there were 20 clusters, 86 households and 177 cases from the initial outbreak.

Dr Smyth said the key message to take from such a spread was to note how quick the virus can transmit, with the new variant first identified in the UK leading to around a third of household contacts of confirmed cases in Ireland testing positive.

"If you display any symptoms of Covid-19, you must immediately self-isolate in your room and phone your GP," she said.

"We know how to break the chains of transmission of this disease. We must all continue to make every effort to limit our social contacts, stay home and stay safe."