Case definition and clinical testing guidelines for COVID-19

Last updated: 19 August 2021

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
• Instructions for specimen collection
• Clinical criteria for COVID-19
• Higher Index of Suspicion (HIS) criteria
• Case classification
• Notification procedure

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.

Instructions for specimen collection

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

• COVID-19 Instructions on specimen collection (PDF 275KB)
• COVID-19 Instructions on specimen collection (Word 314 KB)

Clinical criteria for COVID-19

The following symptoms are consistent with COVID-19.

Any acute respiratory infection with at least one of the following symptoms (with or without fever): 

• fever (at least 38˚C)
• new or worsening cough
• sore throat
• shortness of breath
• sneezing and runny nose (coryza)
• anosmia (loss of sense of smell) or dysgeusia (altered sense of taste).

People meeting the clinical criteria for COVID-19 should be tested. Some people may present with less common symptoms such including diarrhoea, headache, myalgia (muscle aches), nausea, vomiting, or confusion/irritability. For people with less common symptoms, if there is not another more likely diagnosis, they should also be tested.

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 and day 12 following exposure. Notify the Medical Officer of Health Self-isolate1 for 14 days following exposure and until released by public health official Household Contacts of a Close Contact must stay at home until the Close Contact receives a negative result from their day 5 test.
	Casual Plus Contact	Typical symptoms Less typical symptoms with no other likely diagnosis	Test immediately and on day 5 Stay at home2 while day 5 test result is pending and until 24 hours after symptoms resolve. If symptoms develop after day 5, test and stay at home while test result is pending.
	Casual Contact	Typical symptoms Less typical symptoms with no other likely diagnosis	Test Stay at home2 while test result is pending and until 24 hours after symptoms resolve
	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 as per advice from Ministry of Health and/or public health unit immediately, on day 5 and day 12 Self-isolate1 for 14 days and until released by public health official
	Casual Plus Contact		Test immediately and on day 5. Stay at home2 while test result is pending
	Casual Contact		No test required unless symptoms develop. Self-monitor for COVID-19 symptoms for 14 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. 

Notification procedure

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).