Publication - Advice and guidance

Coronavirus: how contact tracing works

Information from Scotland's Deputy Chief Medical Officer Gregor Smith.

10 Mar 2020
Coronavirus: how contact tracing works

A highly effective way to protect the public from infections like Coronavirus (COVID-19) is through a method called contact tracing.

This is used to prevent the spread of infection, and to provide a rapid response to those who might be newly infected. It is a fundamental part of outbreak control, used by public health professionals around the world.

Once a patient has tested positive for the virus, work is carried out to identify anyone who has had close contact with them during the time they are considered to have been infectious.

How does contact tracing work?

Those who test positive for coronavirus will speak to a clinician who gathers detailed information on places they visited and people they came into close contact with since they became unwell or, in the case of international travellers, since they arrived in the UK.

This builds a very specific picture of the people who need to be contacted, such as family members, colleagues or fellow travellers.

What is close contact?

A close contact can be defined as someone living in the same household, someone who had direct or physical contact with an infected person, or someone who has remained within two metres of the patient for longer than 15 minutes.

People who have passed the patient in the street or in a shop are at very low risk and will not be traced.

What about people who have travelled during the time they may have been infectious?

If there is a Scottish patient who has recently been to another country or territory, the public health authorities over there are notified to investigate potential contacts and take steps to prevent further cases.

Equally, communication remains open with other parts of the world to discover if any patients overseas might have spent time in Scotland, and require investigation around people they have had contact with.

What advice is given to close contacts?

Mainly information on what to do if they become unwell or develop certain symptoms.

Anyone believed to be at higher risk of infection could be asked to self-isolate – remaining within their home and avoiding public places. These people will be in daily contact with health experts until they are given the all-clear.

Should a person develop symptoms, they are tested and given specialist care if they prove to be positive for the virus.

What is the evidence that contact tracing works?

It is a tried and trusted approach used for many years to prevent the spread of infection and to contain and stop outbreaks. Contact tracing is an important part of epidemiologic investigation and active surveillance.

For example, it is used to investigate cases and outbreaks of Tuberculosis. But the principles apply to any infectious disease.

Will contact tracing always be used?

This very much depends on the phase of the outbreak. These include:

  • contain – the early phase where we attempt to contain the spread by rapidly tracking down patients and giving the appropriate treatment
  • delay – taking steps to delay the peak of the outbreak, which could include reducing the number of large scale gatherings
  • mitigate – providing the best care for those who have become ill and supporting the delivery of essential services

The response to coronavirus is under constant review and informed by a range of public health experts and scientists.

Contact tracing may continue to successfully contain the virus, or we could reach a point of sustained transmission when we’d rely less on contact tracing.

The focus would then shift to providing the best care to help those who have developed COVID-19, to delaying and reducing the spread as much as is possible and to protecting those who are particularly vulnerable.

Why aren’t the public told exactly where confirmed cases are?

Patient confidentiality must be protected. People have rights to their own privacy and public services have responsibilities to respect those rights. 

Contact tracing services work with patients and maintain their confidentiality. The interventions that contact tracing allows will protect other people and mean we don’t have to share details with those who are not affected or at risk. 

What if more coronavirus cases are confirmed?

Health staff have considerable experience at using contact tracing to prevent and contain outbreaks to keep the public safe.

If the virus becomes more established we may need to move to a different phase of the response which focuses less on containment.

But we are not there yet.

How can I reduce my risk of catching coronavirus?

We are still learning about coronavirus, but we know that similar viruses spread through droplets from coughing and sneezing.

Simple actions are most effective to help stop germs spreading:

  • wash your hands regularly with soap and water, or use a sanitiser gel
  • avoid touching your eyes, nose and mouth with unwashed hands
  • avoid close contact with people who are unwell
  • catch a cough or sneeze in a tissue, then bin it and wash your hands