"It's very shocking for a lot of people to get a phone call to say they have Covid-19. We give them a few hours to think about who they have seen, but it can be overwhelming," said Kim Sayers, a contact tracer with the HSE.

She is among a team of 280 contact tracers making 800 tracing calls every day in centres across Galway, Limerick, Dublin and Cork. The HSE is actively recruiting 550 dedicated contact-tracers.

"A call-one is when someone is getting a positive diagnosis.These calls are usually carried out by clinicians," said Paul Gillen, who was the shift leader at the HSE's national tracing team this week, which is located on the campus of the NUI in Galway.

"A call-two is when we phone those people back to get their close contacts, and a call-three is when we phone those close contacts to let them know."

Ms Sayers said the Covid-19 app, which has now been downloaded by 1.3m users, has supported the contact tracing work, picking up people that may have been missed when tracing close contacts.

"The app gives an extra comfort level that we have picked up on other people, if someone doesn't give a name or doesn't remember meeting someone, the app will send an alert to a person to say they have been a close contact."

The team in Galway has dedicated a number of staff to dealing with positive cases in schools. Although 64 schools have had public health risk assessments and 30 have had class or pod testing since the beginning the of the school term, the detection rate has been low with just a handful of positive cases so far.

"Relative to the one million children heading back to schools, the numbers have been low," according to Dr Sarah Doyle, the HSE's Clinical lead for the Contact Management Programme.

Contact tracers are currently contacting close contacts of approximately five or six people per positive case, but some cases can have as many as 50 close contacts. 

Examples of cases that give rise to a high number of close contacts include workplaces, family gatherings, and school environments.

"At the moment, the average number of contacts per positive case is between five and six," said Dr Doyle.

"The median is a little bit lower. What that tells us is that there are a small number of people who have a lot of contacts."

Among the more complex calls for the tracers has been those involving migrant workers where English is not their first language, and an interpreter is required to join the call.

"We were calling them up giving them a positive diagnosis, and there was huge fear around what happens next, will you tell my employer?" said contact tracer Triona Fehily, on secondment from her job as a Senior Occupational Therapist.

Some of those cases were further complicated by the living arrangements of workers, who might have been sharing accommodation and had spouses or partners who worked in health care setting, a "double whammy" for the contact tracers, Ms Fehily added.

Contact tracer Siobhan Lawlor, who is an Environmental Health officer, said the calls vary a lot  - from young asymptomatic cases, to elderly people who may be very upset at the diagnosis and need extra time to digest the news and work out the next steps.

"Last week I was on a call for an hour-and-a-half, nearly two hours with an elderly person who was on their own, in their own home, and quite upset on the phone. You try to be compassionate with them, as you go through the assessment and guidelines with them,"

Monica Coughlan is among 80 volunteers from the NUIG staff who were trained by the HSE to work as contact tracers, temporarily leaving her job as librarian in the college. She also said many callers needed reassurance and help in working out how to isolate.

"There was a lot of scenarios where people couldn't totally isolate, they were very distressed," she said.

Although the team of contact tracers know their work is critical, those on secondment from other parts of the HSE are concerned about the work they have left behind.

Ms Feehily said she worries about her OT patients: "There is huge concern among all of the therapy staff that have been redeployed to contact tracing.

"While we acknowledge the importance of this job and it is essential in the national interest, there is a whole cohort out of people out there not receiving services because we are here contact tracing."