How contact tracing works

What contact tracing is, types of contact, and locations of interest and what you should do if you visited one.

What contact tracing is

If someone has COVID-19, the Ministry of Health and district health boards (DHBs) track down people who may have been exposed to the virus. This process is called contact tracing.

More about contact tracing at the Ministry of Health (external link)

Types of close and casual contacts

There are several types of ‘contacts’:

  • close plus contacts
  • close contacts
  • casual plus contacts, and
  • casual contacts.

The Ministry of Health gives advice to all these types of contacts on what they need to do.

Close or close plus contacts

Close contacts or close plus contacts are those who are likely to be at a higher risk of being infected.

If you have been identified as a close contact or close plus contact of someone with COVID-19, the Ministry of Health or your Public Health Unit will contact you.

Advice and actions for close contacts or close plus contacts at the Ministry of Health (external link)

Casual plus contacts

Casual plus contacts are people who have had exposure to a case, but who do not meet the criteria of a close contact. For casual plus contacts, their contact was where there is higher risk for transmission.

In some specific higher-risk situations, the Ministry of Health may contact you if you are a casual plus contact.

Advice and actions for casual plus contacts at the Ministry of Health (external link)

Casual contacts

Casual contacts are people who have had exposure to a case, but who do not meet the criteria of a close contact or a casual plus contact. 

Advice and actions for casual contacts at the Ministry of Health (external link)

Locations of interest

Locations of interest are places where someone confirmed with COVID-19 visited.

If you visited a location of interest at a certain time, depending on the circumstances you may be classed as a contact. There are different levels of contact — the Ministry of Health lists locations of interest and has advice on what you need to do if you are a contact. 

Locations of interest in New Zealand (external link)

How contact tracing works using the NZ COVID Tracer app

The NZ COVID Tracer app is our fastest way of responding to the virus — the faster we respond, the faster we stop it. The app also keeps people informed of the risk.

1. COVID-19 is detected in the community

Usually this is from a test, someone visiting a doctor when ill or calling Healthline.

2. The person with COVID-19, and people living and working with them, are interviewed

They will be asked if they have used the official NZ COVID Tracer app to scan QR codes:

  • If they have, this gives us all the information needed to quickly start pinpointing the source of a cluster/community transmission and anyone else who may have been exposed to the virus. It also helps if they have also taken notes for those times when the QR code wasn’t available.
  • If they have not, there's a much more lengthy process to find out the same answers. This slows things down considerably, allowing COVID-19 more time to spread to others in the community.

3. An alert may be issued on the app

  • If the person was using the app and scanning QR codes, we can be certain of where they were at exact times. An alert can be issued via the app, warning others of the risk.
  • If they were not using the app, an alert probably will not be able to be sent — to avoid sending false alerts and worrying people needlessly.

4. Others who receive the alert self-assess and decide whether to contact Healthline

  • If an alert does go out, anyone who has been using the app instantly receives information telling them they may have been exposed to COVID-19. They then self-assess whether they or anyone they know has symptoms, and get in touch with Healthline if they do.
  • People who do not have the app will not be able to receive the alerts. That means there may be a delay before they find out if there is a threat of the virus in their community.

How you can help make contact tracing easier

You can help make contact tracing easier for health officials by continuing to keep a record of where you go and who you meet.

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