Case definition and clinical testing guidelines for COVID-19

Case definition and clinical testing guidelines for health practitioners

Last updated: 25 November 2021

Summary of changes:

16 November – Updated actions for testing in primary care and community.

15 November – Updated Close Contact requirement to self-isolate for at least 10 days, instead of 14 days.

30 September – Adjustment to symptoms (common and less common) and the time of onset after a person has been infected.

This page provides guidance to support health professionals to identify and test those individuals who may have a higher risk of having COVID-19. It includes clinical criteria of COVID-19, the Higher Index of Suspicion (HIS) criteria, case definitions and notification procedures.

For more information on testing refer to: the COVID-19 Testing Plan, which outlines a systematic risk-based approach to testing at the border, in the community, and for containment or cluster management purposes; and Testing Guidance for the Health Sector, which contains more detailed advice that will be regularly updated to take into account New Zealand’s current situation including COVID-19 Alert Level status.

On this page:

Guidelines for testing

People should be tested who have symptoms that meet the clinical criteria for COVID-19 (detailed below). 

Where people meet the clinical criteria for COVID-19 and also meet the HIS criteria, extra steps (self-isolation and notification) are needed.

People may also be tested when they are asymptomatic and:

  • they are required to undertake mandatory routine testing at specified intervals (e.g., border and MIQ workers),
  • they are contacts of confirmed (or probable) cases. 

For definitions and guidance on management of contacts (e.g. Close, Casual Plus and Casual Contacts) see Contact tracing.

Types of testing

Instructions for specimen collection

Guidance on how to take nasopharyngeal, and oropharyngeal + anterior nasal specimens for COVID-19.

Clinical criteria for COVID-19

Common symptoms of COVID-19 are similar to colds or influenza. A person may have one or more of the following symptoms

Common symptoms:

  • new or worsening cough
  • sneezing and runny nose 
  • fever
  • temporary loss of smell or altered sense of taste
  • sore throat
  • shortness of breath.

Less common symptoms of COVID-19 may include diarrhoea, headache, muscle aches, nausea, vomiting, malaise, chest pain, abdominal pain, joint pain or confusion/irritability. These almost always occur with one or more of the common symptoms.

Symptoms tend to arise around two to five days after a person has been infected but can take up to 14 days to show. The virus can be passed to others before they know they have it-from up to two days before symptoms develop,

Other conditions that require urgent assessment and management should always be considered as possible diagnoses alongside COVID-19.

Higher Index of Suspicion (HIS) criteria

People who meet the HIS criteria are those who have, in the 14 days prior to symptom onset:  

  • travelled internationally (excluding travel by air from a country/area with which New Zealand has quarantine-free travel (QFT)*),
  • had direct contact with a person who has travelled internationally in the preceding 14 days (excluding travel by air from a QFT country/area). e.g. Customs and Immigration staff, staff at quarantine/isolation facilities,
  • exited an MIQ facility (excluding recovered COVID-19 cases),
  • worked on an international aircraft or shipping vessel (excluding aircraft from a QFT country/area), 
  • cleaned at an international airport or maritime port in areas/conveniences visited by international arrivals (excluding areas/conveniences for travellers by air from a QFT country/area), 
  • worked in cold storage areas of facilities that receive imported chilled and frozen goods directly from an international airport or maritime port, or 
  • travelled from an area with an evolving COVID-19 community outbreak (including in New Zealand and in any country/area with which New Zealand has QFT), or 
  • any other criteria requested by the local Medical Officer of Health. 

*a list of QFT countries/areas can be found on the Unite Against COVID-19 website. QFT only refers to travel by air at this point. 

People meeting the HIS criteria who also meet the clinical criteria for COVID-19 (a HIS person) should be tested for COVID-19 and self-isolate while awaiting test results to reduce the risk to others. Notification of the HIS person needs to be made to local Medical Officer of Health.

Table 1: Testing in primary care and community

Presentation

Action

Symptomatic

Higher index of suspicion

Typical symptoms

  • Test
  • Notify the Medical Officer of Health
  • Self-isolate1 while test result is pending and until 24 hours after symptoms resolve and cleared by a health official

Less typical symptoms with no other likely diagnosis

Close Contact

Typical symptoms

Less typical symptoms with no other likely diagnosis

  • Test immediately, on day 5 (all contacts) and day 8 (if household member or not fully vaccinated) following exposure.
  • Notify the Medical Officer of Health
  • Household members of a case: self-isolate for 10 days following exposure (regardless of vaccination status) and test immediately and on day 5 and day 8 after last exposure
  • Others not fully vaccinated: self-isolate for 10 days following exposure and test on day 5 and day 8 after last exposure
  • Others fully vaccinated: self-isolate for 7 days following exposure and test on day 5 after last exposure

Casual Plus Contact

Typical symptoms

Less typical symptoms with no other likely diagnosis

  • Unvaccinated contacts only
  • Test immediately and on day 5
  • Stay at home for 7 days AND until a negative day 5 test is received
  • If symptoms develop after day 5, test immediately and stay at home until a negative test result is received

Casual Contact

Typical symptoms

Less typical symptoms with no other likely diagnosis

  • Test
  • Self-monitor for COVID-19 symptoms for 10 days
  • Test and stay at home if COVID-19 symptoms develop until a negative test result is received

Not higher index of suspicion or contact

Typical symptoms

  • Test
  • Stay at home2 while test result is pending and until 24 hours after symptoms resolve

Asymptomatic

Surveillance testing: Border worker including managed isolation or quarantine facilities

  • Test as per Border Order3
  • No need to isolate following a surveillance test unless they also meet any Close or Casual/Casual Plus criteria as described above.

Surveillance testing: New Zealand-based air crew

  • Test as per requirements4
  • No need to isolate following a surveillance test unless they also meet any Close or Casual/Casual Plus criteria as described above.

Close Contact

  • Test immediately, on day 5 (all contacts) and day 8 (if household member or not fully vaccinated) following exposure
  • Notify the Medical Officer of Health
  • Household members of a case: self-isolate for 10 days following exposure (regardless of vaccination status) and test on day 5 and day 8 after last exposure
  • Others not fully vaccinated: self-isolate for 10 days following exposure and test on day 5 and day 8 after last exposure
  • Others fully vaccinated: self-isolate for 7 days following exposure and test on day 5 after last exposure

Casual Plus Contact

  • Unvaccinated contacts only
  • Test immediately and on day 5
  • Stay at home2 for 7 days AND until negative day 5 test is received.
If symptoms develop after day 5, test immediately and stay at home until a negative test result is received

Casual Contact

  • No test required unless symptoms develop.
  • Self-monitor for COVID-19 symptoms for 10 days.
  1. More information is available under Self-isolation guidance.
  2. More information is available under Staying at home
  3. More information on Border Orders is available at Epidemic notice and Orders.
  4. More information on requirements for international airline crew is available at Aviation sector.
Table 2: Testing in hospital including emergency departments

Presentation

Action

Symptomatic

Higher index of suspicion or a contact

Typical symptoms

  • Test1
  • Notify the Medical Officer of Health
  • Isolate while test result is pending and until clearance

Less typical symptoms with no other likely diagnosis

Not higher index of suspicion or a contact

Typical symptoms

  • Test1
  • Manage as per local infection prevention and control protocols
  1. Testing can be omitted if on clinical assessment there is another clear cause, not a transmissible respiratory infection.

Case classification

Under investigation case

A case that has been notified where information is not yet available to classify it as confirmed, probable or not a case. 

Probable case

  • A close contact of a confirmed case that has a high exposure history, meets the clinical criteria and for whom testing cannot be performed, or
  • A close contact of a confirmed case that has a high exposure history, meets the clinical criteria, and has a negative PCR result but it has been more than 7 days since symptom onset before their first negative PCR test was taken.

Confirmed case

A case that has laboratory definitive evidence. Laboratory definitive evidence requires at least one of the following:

  • detection of SARS-CoV-2 from a clinical specimen using a validated NAAT (PCR). Very weak positive results will only be labelled a confirmed case when the result is confirmed on a second sample.
  • detection of coronavirus from a clinical specimen using pan-coronavirus NAAT (PCR) and confirmation as SARS-CoV-2 by sequencing
  • significant rise in IgG antibody level to SARS-CoV-2 between paired sera.

Not a case

An ‘under investigation’ case who:

  • has a negative test and has been assessed as not a case;
  • a person where SARS-CoV-2 has been detected where the detection is determined to be due to a previous COVID-19 infection which has already been recorded either in New Zealand or overseas; 
  • a person who has detection of SARS-CoV-2 from a clinical specimen but, following further investigations such as serology, repeat testing, history and symptoms, they are deemed to not be a case (e.g. a likely false positive).

Historical case 

A confirmed case that is deemed to have recovered (no longer considered infectious) at the time of testing. 

Case Isolation Requirements

Vaccination status of immunocompetent case

Case isolation requirements

Full**

  • Self-isolate from other household members where possible, in particular away from unvaccinated household members.
  • Mask wearing and physical distancing in shared spaces.
  • Release from isolation after 10 days and provided previous 72 hours symptom free.

Partial or none

  • Self-isolate from other household members where possible, in particular away from unvaccinated household members.
  • Mask wearing and physical distancing in shared spaces.
  • Release from isolation after 14 days and provided previous 72 hours symptom free.

** Full is greater than or equal to 7 days following the second dose for the Pfizer vaccine. 

Note that symptom free should be interpreted as free from most acute symptoms and/or symptoms improving.

Notification of cases

Laboratories must immediately notify the local Medical Officer of Health of any confirmed cases.

Attending medical practitioners must notify the local Medical Officer of Health of any confirmed cases, people they believe may be probable cases AND anyone who meets both the clinical and HIS criteria (notification should include the symptoms meeting the clinical criteria and how the HIS person meets the HIS criteria).

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