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How Contact Tracing Works


Specialist health professionals are working hard to test and contact trace confirmed cases of novel coronavirus (COVID-19) in NSW.


Contact tracing is a process used to understand how an infectious disease is spreading in a community. Contact tracing has two purposes:


  1. to figure out who a sick person caught an illness from, and

  2. to find out who they’ve been in contact with while infectious.

When a person in NSW is diagnosed with an infectious disease like coronavirus (COVID-19), we use contact tracing to figure out where they caught the virus and who they might have passed it on to. Contact tracing is a process conducted by health professionals all around the world, and in NSW, we have specialist teams who spring into action when a situation like the current COVID-19 pandemic occurs.

This article will step you through how contact tracing is happening for COVID-19, why we do it in the way we do, and why it’s such an important part of keeping the public safe.

How does contact tracing for COVID-19 work? When a person in NSW is diagnosed with COVID-19, the Public Health Unit (PHU) for the area they live in is notified. The PHU is staffed with infectious disease specialists, whose job is to understand how diseases like COVID-19 spread. These specialists work with the person who is unwell to trace their movements back to the potential person who they caught the virus from. At the moment in NSW, we can still trace almost every case back to another confirmed case or high-risk activities, like having recently travelled overseas.

It’s important that we do this backward tracing, so that we can understand how the virus is spreading in the NSW community. As it becomes more widespread, it may become more difficult for the PHU experts to figure out where each infected person came into contact with the virus.

Notifying people at risk The second stage of contact tracing involves getting in touch with people who may have been in contact with and infected by the person confirmed to have the disease. When it comes to COVID-19, people can incubate the disease for over a week before they show symptoms and realise they have been infected. This means they need to backtrack to remember all the people they’ve recently been in contact with, which can be tricky work. The PHU specialists will help them be as clear as possible about where they’ve been and who they’ve seen.

Where possible, the people who are at risk of having been infected will be contacted directly by the PHU and given instructions about what they need to do. If it’s not possible to contact people one-on-one, we instead put out a public health alert with the details of the person’s movements, so the public can help us get in touch with those who might have come into contact with the person with the infection. So far, we’ve done this for cases where people have worked in shopping centres or attended university classes, and may have been in close contact with people they don’t personally know.


Not all Details are Released

There are a number of reasons why it’s not a good idea, or even legal, to give the public all the details about the movements of a confirmed case while they might have been infectious, if we can contact people at risk directly instead.


Because of how COVID-19 spreads, we know it’s very unlikely a person will catch it from someone without spending a significant amount of time with them. You are at higher risk of infection if you have had face-to-face contact with a confirmed case for 15 minutes or more, or you’ve shared an enclosed space with them for more than two hours. The risk for people that may have passed a confirmed case on the street or in a shop is extremely low, because we know you probably won’t catch this particular virus in those situations.


If we told you, though, that you’d possibly crossed paths with someone who is a confirmed case, it might actually cause negative impacts for you, even though you most likely haven’t contracted the virus. You might become anxious about getting sick, or miss work, school or other activities because you think you need to self-quarantine. It can also put a massive strain on the health system, because a lot of people who are not at risk become worried they have the virus and require medical attention.


Releasing extra details about confirmed cases can also be unsafe for them. If we publicly released information about where a person lived or where they worked when we didn’t need to, it could impact their personal safety, the privacy of their family, and the security and success of their workplace. Our contact tracing is done so well that we don’t need to release this information and run these risks.


There are also privacy laws to limit the kinds of information that can be shared publicly about a person receiving healthcare with us. These laws protect the privacy of all NSW residents and we abide by them during all situations.

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