Enviromental Health Service HSE team at Dublin Airport activating the public awareness campaign for COVID-19. Sam Boal/

Coronavirus: What is contact tracing and who is considered a 'close contact'?

Health authorities have processes in place that will still be necessary even as the number of cases here rises.

AT THEIR DAILY press briefing at the Department of Health in Dublin, officials constantly repeat that “the process of contact tracing is under way” regarding confirmed cases of Covid-19 in Ireland.

Put simply, contact tracing is when health authorities try to trace who’s been in close contact with someone who has infection to see who else may be at risk of catching it.

In this case, it’s about seeing who someone diagnosed with Covid-19 has been in contact with, what extent they were in contact with them and establishing if that person is at risk of catching the virus themselves.

As always with these things, there are a range of different bodies offering advice on best practice, which are broadly all similar.

The Health Protection Surveillance Centre (HPSC) in Ireland, the European Centre for Disease Prevention and Control (ECDC) and the World Health Organization (WHO) all separately have guidelines and advice on contact tracing.

Let’s take a look at it and what it involves.

Confirmed case

So, when a case is confirmed and the person is receiving appropriate treatment, the next step is to identify close contacts of that person first.

The HPSC lists a number of definitions as to what that includes:

  • Any individual who has had greater than 15 minutes face-to-face (2 metres or less) contact with a confirmed case, in any setting.
  • Household contacts defined as living or sleeping in the same home, individuals in shared accommodation sharing kitchen or bathroom facilities and sexual partners.
  • Healthcare workers, including laboratory workers, who have not worn appropriate personal protective equipment during exposures to a confirmed case.
  • Passengers on an aircraft sitting within two seats (in any direction) of the Covid-19 case, travel companions or persons providing care, and crew members serving in the section of the aircraft where the patient was seated.
  • For contacts who have shared a close space with a confirmed case for longer than two hours, a risk assessment should be undertaken taking into consideration the size of the room, ventilation and the distance from the case. This can include office and school settings.

It also lists casual contacts and the appropriate action to take with them. Casual contacts are defined as of low risk of getting the virus. They could’ve been in a closed environment with a confirmed case for less than 15 minutes, or at a distance of more than two metres. The same applies to face-to-face contact. 

A casual contact could also be someone who took the same mode of transport as a confirmed case. Again, these people are at a low risk of contracting Covid-19 but health authorities will still attempt to trace these people. 

It recommends contact tracing to take place immediately after a confirmed case of Covid-19 or a highly likely suspected case is identified.

The contract tracing is undertaken by public health workers in conjunction with the GP and hospital team. This team can include an infectious disease consultant, admitting physician, infection prevention and control, clinical microbiologist and occupational health physician.

Community-based contacts will be identified and monitored by public health staff, while healthcare workers and hospital in-patient contacts will also be monitored.

It suggests all persons identified as having had contact with a confirmed case should be assessed as to whether they’re a casual or close contact. 

What happens then

Based on the risk assessment made by the health teams, there are two types of follow up done as part of contact tracing - active follow up and passive follow up.

Active follow up is when a person is provided with health advice, contacted on a daily basis and asked about relevant symptoms for 14 days after the last exposure to a confirmed case of Covid-19.

Passive follow up, meanwhile, is when an individual is advised to self-monitor for symptoms and contact their local public health department if they develop symptoms within 14 days after the last exposure to a patient with Covid-19.

Active follow up is recommended for close contacts for 14 days after the last possible exposure to a confirmed case. They should be advised about their risk and provided with a contact tracing pack (more on that below, and in this link), including a face mask. 

contact tracing 1

People subject to active follow up should be advised to self-isolate as much as is practical, including not going to school, work or attending large gatherings.

To help with the risk assessment, the HSE has drafted a form that must be filled out for each close contact.

Based on the answers in this questionnaire, health authorities can prioritise which contacts to monitor more closely.

hse form

The contact tracing information pack is recommended to be sent to all those identified as close contacts and passive contacts.

It’s a letter advising them of their risk of contracting Covid-19, along with detailed diagrams on good handwashing technique and respiratory hygiene.

What the ECDC and WHO says

In its guidance, the ECDC provides advice on what health authorities should do when contact tracing, what training staff need and what resources should be made available to them. 

In many cases, the European health body says just one staff member is needed for the different processes involved, with the time taken for each step ranging from 15 minutes to six hours.

The six-hour task involves the creation of the “contact list” and the retrieval of “personal information”. “This may require collaboration with other entities, including transport authorities, companies and hospitals,” the ECDC says.

The WHO, meanwhile, lists “three basic steps” for health workers to operate a contact tracing system.

They are “contact identification, contact listing and contact follow up”, all of which are in the HPSC and the ECDC guidelines. 

Contact tracing in Ireland now

All of these activities have been undertaken in relation to the confirmed cases in Ireland.

In relation to the first confirmed case, extra precautions taken included closing the school the boy attended in Glasnevin in Dublin 9. 

Contact tracing began on Saturday to try to notify all the close and passive contacts of that individual.

Aside from this one case, the HSE confirmed on Thursday that “many people” have been asked to self-isolate over the risks around Covid-19.

It is likely a number of these would’ve been asked to self-isolate on foot of this contact tracing process. 

However, as the number of cases rise, particularly if there are more clusters like the cases in the west of the country this will add to the workload of health authorities as they try to contain the spread of the virus in Ireland.

Nevertheless, the ECDC recommends that contact tracing is still important to do even when health services are dealing with a large number of patients.

It says: “The point at which extensive contact tracing becomes unsustainable due to limited resources will vary between different countries in the EU/EEA.

It must be emphasised, however, that there is still value in tracing contacts even if not all contacts of each case are traced.
This will help slow the spread of infection and if, on average, less than one new case arises from each case, the outbreak can be contained.

It does say that additional resources would be needed to continue contact tracing among a larger outbreak.

The ECDC does warn, however, that contact tracing may need to be scaled up “very quickly” if the number of identified cases becomes large in a short period of time. 

“In a scenario of widespread transmission contact tracing could still contribute to delaying the spread and reducing the pressure on the healthcare system, but may not be feasible,” it says.

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