The first comprehensive study of community transmission of Covid-19 in the State has identified shops as the most likely source of infection.

Since March 31st, contact tracers investigating confirmed cases have been going back seven days instead of two days in an attempt to identify how people got infected.

Of the 3,476 positive cases since then, 787 (22 per cent) were as a result of community transmission, where the source of infection is not known. More than 60 per cent of these community transmission cases were recorded in Dublin.

Hospital Report

Of those who did not know the source of their infection, 55.8 per cent mentioned shops as the most likely place they would have picked up the disease in the previous seven days.

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This was followed by workplaces (15.6 per cent), primary schools (3.8 per cent), public transport or car sharing (3.5 per cent), travel at home or abroad (2 per cent), outdoor gatherings (1.9 per cent), pre-school gatherings (1.8 per cent) and outdoor sports activities (1.7 per cent).

Almost 9 per cent listed “other” as being a potential source not listed on the Health Service Executive (HSE) questionnaire and seven people said they knew no possible source of transmission.

Niamh O’Beirne, the HSE’s national lead for track and trace, said the findings of the contract tracers do not mean that shops are necessarily unsafe environments.

“All the list tells you is where people were. It does not tell you that you got it there. The high numbers from shops reflect where people have been,” she said.

“Having identified possible sources, we have to then go further and identify the actual sources.”

The number of those stating they tested positive after attending social gatherings such as funerals, birthday parties, hairdressers or salons was too small to be measured.

Ms O’Beirne said if a person believed they were infected at a social gathering, that social gathering is investigated and it usually leads to other cases.

As the source of infection is then known, it is not included among the community transmission cases.

The Covid-19 walk-in test centres tested 25,413 people at 14 centres nationwide. Finglas and Blanchardstown had the highest positivity rate of more than 4 per cent, the average positivity rate was 2.6 per cent.

To date, 635 Covid-19 cases have been identified through the centres. They were intended for those who were asymptomatic, but half of those who tested positive did have symptoms and 40 per cent have been subsequently identified as close contacts of confirmed cases.