THE HSE HAS revealed plans to begin investigating where people are being infected with Covid-19 as part of a new “retrospective contact tracing” policy.
The National Public Health Emergency Team (NPHET) endorsed a proposal to conduct enhanced tracing in September. The plan was delayed, however, due to a spike in cases in October and delays with Ireland’s Testing & Tracing programme.
In a statement to TheJournal.ie, the HSE said “enhanced contact tracing” for routine cases of Covid-19 will commence in early December.
The aim is to gather additional information on Covid-19 cases labelled as ‘community transmission’ – where the source of the infection is unknown – and will involve a series of questions in order to build a more accurate picture of where people are contracting the virus.
The HSE has said that it is important to start enhanced contact tracing while the incidence of disease is low.
The aim is that it will ensure Ireland’s Testing & Tracing system is prepared to identify early infections. This could lead to quicker local interventions after Level 5 restrictions are lifted.
Up until now contact tracing teams have asked people about their close contacts and movements up to 48 hours before they develop symptoms rather than pinpointing where they could have been infected.
Enhanced tracing has previously been carried out by Public Health teams for cases in complex settings only such as nursing homes, Direct Provision centres and meat processing plants.
Enhanced tracing will now be carried out by contact tracers throughout Ireland for otherwise routine cases of community transmission, which has spiked since cases began to rise in September.
Following NPHET’s recommendation in late September that bars and restaurants in Dublin stop serving customers indoors, there were calls for officials to provide concrete evidence that transmission had been linked to these settings.
At the time, NPHET’s epidemiological modelling advisory group chair Professor Philip Nolan said Public Health teams’ priority was tracking where the virus was spreading and preventing onward transmission but added that retrospective tracing would be important in the future.
“We would like to go back and find out where people are getting the virus, but we don’t have the time or resources to pursue this academic exercise,” he said on 18 September.
It is estimated that in the fortnight up to 10 November, 33% of cases are linked with community or possible community transmission – where the source of infection is not known.
A spokesperson for the HSE said confirmed cases will be asked to describe their activities and contacts for up to 14 days prior to symptom onset.
“This facilitates the identification of possible sources of their infection and identification of other contacts that may require monitoring,” they said.
Under the new system, when confirmed cases are first contacted by tracers they will be asked “key questions” regarding visits to healthcare settings, visits to friends or relatives as well as questions around restaurants, pubs and cinemas in order to pinpoint if a particular setting is high-risk and requires intervention by Public Health teams.
People will also be asked questions about visits to special events, including weddings and christenings, up to 14 days prior to symptoms developing.
In addition, contact tracers will also pinpoint movements around sports and exercise, public transport, religious services and visits to hairdressers and nail bars.
Data will be gathered and analysed to identify key settings where exposure to Covid-19 most likely occurred and potential hot spots of infection.
In a letter to the Government in September, Deputy Chief Medical Officer Dr Ronan Glynn said: “Such an approach will allow the environments and activities associated with the greatest levels of transmission be more accurately and quickly identified.”
In its guidelines, the European Centre for Disease Prevention and Control (ECDC) says contact tracing should “rapidly identify secondary cases that may arise after transmission from the primary known cases in order to intervene and interrupt further onward transmission”.
Modelling studies suggest that adding an element of retrospective contact tracing to regular contact tracing may reduce the effective reproduction number, the HSE spokesperson said.
Ireland’s R-number is currently estimated at between 0.7 and 0.9 having fallen from 1 the previous week.
Health officials last night confirmed 362 further cases of Covid-19 in Ireland and two more deaths.
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