View Article PDF

We report the earliest known cluster of SARS-CoV-2 infection so far reported, which occurred in New Zealand in late February 2020. The cluster includes one confirmed and five probable cases.

The cluster was identified while investigating a weak positive nasopharyngeal swab (NPS) polymerase chain reaction (PCR) test that was returned by a male in his 60s in September 2020. The PCR result, combined with a clear clinical and epidemiological history of a COVID-19 like illness in late February 2020, prompted serological testing. SARS-CoV-2 IgG antibodies were detected and supported historical infection. Serology was also reactive for five close contacts who had also experienced a COVID-19 like illness in February 2020.

Combined case histories and investigations suggest that this local cluster was import related, with the index case identified as a family member visiting from Italy in February. Case investigation also suggests this cluster was active in New Zealand prior to any previously documented local cases, indicating that SARS-CoV-2 was present and local transmission was occurring earlier than initially suspected. A weak positive PCR result, six months after acute infection, supports international evidence that SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection, and that this is not necessarily indicative of infectivity.

Case presentation

In early September 2020, a weak positive NPS PCR result (GeneXpert Xpert® Xpress SARS-CoV-2, Cepheid, Sunnyvale, Ca, USA: E gene target CT 40.5; N2 gene 38.2) was notified to the Waikato Public Health Unit.  The male in his 60s presented for testing due to symptoms of sore throat, cough and coryza. The case interviewer was unable to identify a potential source for acute SARS-2-CoV infection. The patient did not meet any of the Higher Index of Suspicion Criteria (criteria that could indicate increased risk of exposure), including no contact with recent COVID-19 confirmed cases (or their close contacts). There was no history of exposure to locations of interest connected to the August Auckland cluster, which was active at the time.1 The case indicated that he suspected infection with SARS-CoV-2 several months earlier.

A family member and close contact of the case had arrived in New Zealand from Italy (Lombardy region) on February 23. This person became unwell shortly after arrival and presented to primary care on February 25 with a flu-like illness that included muscle aches, cough, coryza, sore throat and fever. The individual did not meet the New Zealand Ministry of Health suspected COVID-19 case definition at the time and was not eligible for testing. The individual was advised to follow standard public health advice for ‘flu-like illness’, which included to self-isolate until symptoms had resolved. Over the following four days, six household contacts became unwell with a similar flu-like illness—they followed the same precautions, self-isolating until symptoms had resolved. No one required medical attention.

The individual returned to Italy in mid-June and had SARS-CoV-2 PCR testing and serology completed shortly after. The PCR test was negative; however, the serology (Total IgG/IgM by ECLIA, I.R.C.C.S Ospedale San Rafaele Milan, It) was reactive for SARS-CoV-2 antibodies, indicative of past infection.

Laboratory testing

Serial NPS (four in total) were collected from the case and PCR results were unchanged over nine days, with GeneXpert Ct values over 36 for both targets, which continues to support a past rather than an acute infection. Whole genome sequencing of the weak positive PCR result was not possible due to the low level of genetic material.

Close contacts had NPS PCR testing completed. All, including one who was symptomatic with a coryzal illness, returned negative results. Workplace close and casual contacts were offered nasopharyngeal PCR testing. No additional positive results were reported. The occupation of the case involved frequent contact with the public and, despite intensive screening for both symptomatic and asymptomatic cases in the region, no case had been detected in relation to his workplace.

The case and the five additional household contacts who reported being unwell in February returned reactive SARS-CoV-2 results on the Roche Diagnostics Elecsys total (IgG and IgM) antibody assay (Paul Austin, Auckland City Hospital). The case also had second-line testing conducted using the Euroimmun IgG specific assay and the Wantai SARS-CoV-2 Ab ELISA. This testing confirmed the presence of IgG antibodies.

Discussion

This case report describes an import-related historical case and household cluster of COVID-19 that went unidentified during the early stages of New Zealand’s COVID-19 response. Case histories and investigations suggest that this cluster was active prior to the first reported case of imported COVID-19 and the first reported import-related case of COVID-19 in New Zealand.2

It was concluded that the ‘weak positive’ PCR result returned by the male in his 60s was most likely indicative of historical infection. Risk assessment concluded it was unlikely the case was infectious during their September illness, due to the combination of the weak positive PCR result and the presence of IgG antibodies indicating immunity. The case remained off work and isolated at home while unwell in September. No additional cases of COVID-19 occurred as a result of this case in September.

Identification of this cluster has drawn attention to some of the early challenges faced by New Zealand during the pandemic. This includes determining an appropriate case definition at a time when clinical and epidemiological information is predominantly observational and rapidly changing. The surveillance case definition also dictated allocation of the very limited testing capacity at that time.3

The decision of the New Zealand Government to implement a full-scale, nationwide lockdown in March significantly restricted the international and national movement of New Zealanders.4 This approach saw New Zealand avoid any significant health system shock, and the virus was eliminated from within the community for 102 days.5 The identification of this household cluster, which was epidemiologically linked to a region of Italy that subsequently became a region of international concern, provides evidence that undetected local transmission of SARS-CoV-2 was occurring from at least late February 2020. This finding offers additional evidence that supporting the New Zealand lockdown action and following public health advice for any influenza like illness were effective strategies in reducing transmission, from both identified cases and unrecognised clusters, to the point of elimination.

The finding of a weak positive PCR result 201 days (more than six months) after acute infection indicates SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection. Studies to date suggest that the presence of SARS-CoV-2 viral RNA on a PCR test does not necessarily correlate with infectivity.6–8 We recommend the use of serology coupled with repeat PCR to determine the ‘age’ of the infection, and thus for use as a predictor of infectivity.

Summary

Abstract

We report the earliest known cluster of SARS-CoV-2 infection so far reported, which occurred in New Zealand in late February 2020. The cluster includes one confirmed and five probable cases.

The cluster was identified while investigating a weak positive nasopharyngeal swab (NPS) polymerase chain reaction (PCR) test that was returned by a male in his 60s in September 2020. The PCR result, combined with a clear clinical and epidemiological history of a COVID-19 like illness in late February 2020, prompted serological testing. SARS-CoV-2 IgG antibodies were detected and supported historical infection. Serology was also reactive for five close contacts who had also experienced a COVID-19 like illness in February 2020.

Combined case histories and investigations suggest that this local cluster was import related, with the index case identified as a family member visiting from Italy in February. Case investigation also suggests this cluster was active in New Zealand prior to any previously documented local cases, indicating that SARS-CoV-2 was present and local transmission was occurring earlier than initially suspected. A weak positive PCR result, six months after acute infection, supports international evidence that SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection, and that this is not necessarily indicative of infectivity.

Aim

Method

Results

Conclusion

Author Information

Dr Elizabeth Becker: Public Health Medicine Registrar, Public Health Unit, Waikato District Health Board. Dr Richard Vipond: Public Health Medicine Specialist and Medical Officer of Health, Clinical Director Waikato PHU COVID-19 response; Public Health Unit, Waikato District Health Board. Dr Chris Mansell: Clinical Microbiologist, Waikato District Health Board.

Acknowledgements

Dr Geoffrey Cramp: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Marianne Dowsett: Public Health Medicine Specialist, Public Health Unit, Waikato District Health Board. Dr Richard Hoskins: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Richard Wall: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Felicity Dumble: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Bevan Clayton-Smith: Service Director Public Health, Waikato District Health Board.

Correspondence

Dr Elizabeth Becker: Public Health Medicine Registrar, Public Health Unit, Waikato District Health Board, Private bag 3200, Hamilton, 3204; Dr Richard Vipond, Public Health Medicine Specialist and Medical Officer of Health, Clinical Director Waikato PHU COVID-19 response; Public Health Unit, Waikato District Health Board, Private Bag 3200, Hamilton, 3204

Correspondence Email

elizabeth.becker@waikatodhb.health.nz, richard.vipond@waikatodhb.health.nz

Competing Interests

Nil.

1. Ministry of Health. COVID-19 - Significant clusters: Ministry of Health; 2020 [Available from: https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-current-situation/covid-19-current-cases/covid-19-significant-clusters]

2. Jefferies S, French N, Gilkison C, et al. COVID-19 in New Zealand and the impact of the national response: a descriptive epidemiological study. Lancet Public Health. 2020.

3. Cameron B. Captaining a team of 5 million: New Zealand Beats Back COVID-19, March-June 2020. Princeton School of Public and International Affairs; 2020.

4. New Zealand Government. New Zealand COVID-19 Alert Levels Summary. Unite against COVID-19; 2020 Available from: https://covid19.govt.nz/assets/resources/tables/COVID-19-alert-levels-detailed.pdf]

5. Fouda A, Mahmoudi N, Moy N, Paolucci F. The COVID-19 pandemic in Greece, Iceland, New Zealand, and Singapore: Health Policies and Lessons Learned. Health Policy Technol. 2020.

6. Widders A, Broom A, Broom J. SARS-CoV-2: The viral shedding vs infectivity dilemma. Infection, disease & health. 2020;25(3):210-5.

7. Walsh K, Jordan K, Clyne B, et al. SARS-CoV-2 detection, viral load and infectivity over the course of an infection. J. Infection. 2020;81(3):357-71.

8. Lu J, Peng J, Xiong Q, et al. Clinical, immunological and virological characterization of COVID-19 patients that test re-positive for SARS-CoV-2 by RT-PCR. EBioMedicine. 2020;59:102960.

For the PDF of this article,
contact nzmj@nzma.org.nz

View Article PDF

We report the earliest known cluster of SARS-CoV-2 infection so far reported, which occurred in New Zealand in late February 2020. The cluster includes one confirmed and five probable cases.

The cluster was identified while investigating a weak positive nasopharyngeal swab (NPS) polymerase chain reaction (PCR) test that was returned by a male in his 60s in September 2020. The PCR result, combined with a clear clinical and epidemiological history of a COVID-19 like illness in late February 2020, prompted serological testing. SARS-CoV-2 IgG antibodies were detected and supported historical infection. Serology was also reactive for five close contacts who had also experienced a COVID-19 like illness in February 2020.

Combined case histories and investigations suggest that this local cluster was import related, with the index case identified as a family member visiting from Italy in February. Case investigation also suggests this cluster was active in New Zealand prior to any previously documented local cases, indicating that SARS-CoV-2 was present and local transmission was occurring earlier than initially suspected. A weak positive PCR result, six months after acute infection, supports international evidence that SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection, and that this is not necessarily indicative of infectivity.

Case presentation

In early September 2020, a weak positive NPS PCR result (GeneXpert Xpert® Xpress SARS-CoV-2, Cepheid, Sunnyvale, Ca, USA: E gene target CT 40.5; N2 gene 38.2) was notified to the Waikato Public Health Unit.  The male in his 60s presented for testing due to symptoms of sore throat, cough and coryza. The case interviewer was unable to identify a potential source for acute SARS-2-CoV infection. The patient did not meet any of the Higher Index of Suspicion Criteria (criteria that could indicate increased risk of exposure), including no contact with recent COVID-19 confirmed cases (or their close contacts). There was no history of exposure to locations of interest connected to the August Auckland cluster, which was active at the time.1 The case indicated that he suspected infection with SARS-CoV-2 several months earlier.

A family member and close contact of the case had arrived in New Zealand from Italy (Lombardy region) on February 23. This person became unwell shortly after arrival and presented to primary care on February 25 with a flu-like illness that included muscle aches, cough, coryza, sore throat and fever. The individual did not meet the New Zealand Ministry of Health suspected COVID-19 case definition at the time and was not eligible for testing. The individual was advised to follow standard public health advice for ‘flu-like illness’, which included to self-isolate until symptoms had resolved. Over the following four days, six household contacts became unwell with a similar flu-like illness—they followed the same precautions, self-isolating until symptoms had resolved. No one required medical attention.

The individual returned to Italy in mid-June and had SARS-CoV-2 PCR testing and serology completed shortly after. The PCR test was negative; however, the serology (Total IgG/IgM by ECLIA, I.R.C.C.S Ospedale San Rafaele Milan, It) was reactive for SARS-CoV-2 antibodies, indicative of past infection.

Laboratory testing

Serial NPS (four in total) were collected from the case and PCR results were unchanged over nine days, with GeneXpert Ct values over 36 for both targets, which continues to support a past rather than an acute infection. Whole genome sequencing of the weak positive PCR result was not possible due to the low level of genetic material.

Close contacts had NPS PCR testing completed. All, including one who was symptomatic with a coryzal illness, returned negative results. Workplace close and casual contacts were offered nasopharyngeal PCR testing. No additional positive results were reported. The occupation of the case involved frequent contact with the public and, despite intensive screening for both symptomatic and asymptomatic cases in the region, no case had been detected in relation to his workplace.

The case and the five additional household contacts who reported being unwell in February returned reactive SARS-CoV-2 results on the Roche Diagnostics Elecsys total (IgG and IgM) antibody assay (Paul Austin, Auckland City Hospital). The case also had second-line testing conducted using the Euroimmun IgG specific assay and the Wantai SARS-CoV-2 Ab ELISA. This testing confirmed the presence of IgG antibodies.

Discussion

This case report describes an import-related historical case and household cluster of COVID-19 that went unidentified during the early stages of New Zealand’s COVID-19 response. Case histories and investigations suggest that this cluster was active prior to the first reported case of imported COVID-19 and the first reported import-related case of COVID-19 in New Zealand.2

It was concluded that the ‘weak positive’ PCR result returned by the male in his 60s was most likely indicative of historical infection. Risk assessment concluded it was unlikely the case was infectious during their September illness, due to the combination of the weak positive PCR result and the presence of IgG antibodies indicating immunity. The case remained off work and isolated at home while unwell in September. No additional cases of COVID-19 occurred as a result of this case in September.

Identification of this cluster has drawn attention to some of the early challenges faced by New Zealand during the pandemic. This includes determining an appropriate case definition at a time when clinical and epidemiological information is predominantly observational and rapidly changing. The surveillance case definition also dictated allocation of the very limited testing capacity at that time.3

The decision of the New Zealand Government to implement a full-scale, nationwide lockdown in March significantly restricted the international and national movement of New Zealanders.4 This approach saw New Zealand avoid any significant health system shock, and the virus was eliminated from within the community for 102 days.5 The identification of this household cluster, which was epidemiologically linked to a region of Italy that subsequently became a region of international concern, provides evidence that undetected local transmission of SARS-CoV-2 was occurring from at least late February 2020. This finding offers additional evidence that supporting the New Zealand lockdown action and following public health advice for any influenza like illness were effective strategies in reducing transmission, from both identified cases and unrecognised clusters, to the point of elimination.

The finding of a weak positive PCR result 201 days (more than six months) after acute infection indicates SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection. Studies to date suggest that the presence of SARS-CoV-2 viral RNA on a PCR test does not necessarily correlate with infectivity.6–8 We recommend the use of serology coupled with repeat PCR to determine the ‘age’ of the infection, and thus for use as a predictor of infectivity.

Summary

Abstract

We report the earliest known cluster of SARS-CoV-2 infection so far reported, which occurred in New Zealand in late February 2020. The cluster includes one confirmed and five probable cases.

The cluster was identified while investigating a weak positive nasopharyngeal swab (NPS) polymerase chain reaction (PCR) test that was returned by a male in his 60s in September 2020. The PCR result, combined with a clear clinical and epidemiological history of a COVID-19 like illness in late February 2020, prompted serological testing. SARS-CoV-2 IgG antibodies were detected and supported historical infection. Serology was also reactive for five close contacts who had also experienced a COVID-19 like illness in February 2020.

Combined case histories and investigations suggest that this local cluster was import related, with the index case identified as a family member visiting from Italy in February. Case investigation also suggests this cluster was active in New Zealand prior to any previously documented local cases, indicating that SARS-CoV-2 was present and local transmission was occurring earlier than initially suspected. A weak positive PCR result, six months after acute infection, supports international evidence that SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection, and that this is not necessarily indicative of infectivity.

Aim

Method

Results

Conclusion

Author Information

Dr Elizabeth Becker: Public Health Medicine Registrar, Public Health Unit, Waikato District Health Board. Dr Richard Vipond: Public Health Medicine Specialist and Medical Officer of Health, Clinical Director Waikato PHU COVID-19 response; Public Health Unit, Waikato District Health Board. Dr Chris Mansell: Clinical Microbiologist, Waikato District Health Board.

Acknowledgements

Dr Geoffrey Cramp: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Marianne Dowsett: Public Health Medicine Specialist, Public Health Unit, Waikato District Health Board. Dr Richard Hoskins: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Richard Wall: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Felicity Dumble: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Bevan Clayton-Smith: Service Director Public Health, Waikato District Health Board.

Correspondence

Dr Elizabeth Becker: Public Health Medicine Registrar, Public Health Unit, Waikato District Health Board, Private bag 3200, Hamilton, 3204; Dr Richard Vipond, Public Health Medicine Specialist and Medical Officer of Health, Clinical Director Waikato PHU COVID-19 response; Public Health Unit, Waikato District Health Board, Private Bag 3200, Hamilton, 3204

Correspondence Email

elizabeth.becker@waikatodhb.health.nz, richard.vipond@waikatodhb.health.nz

Competing Interests

Nil.

1. Ministry of Health. COVID-19 - Significant clusters: Ministry of Health; 2020 [Available from: https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-current-situation/covid-19-current-cases/covid-19-significant-clusters]

2. Jefferies S, French N, Gilkison C, et al. COVID-19 in New Zealand and the impact of the national response: a descriptive epidemiological study. Lancet Public Health. 2020.

3. Cameron B. Captaining a team of 5 million: New Zealand Beats Back COVID-19, March-June 2020. Princeton School of Public and International Affairs; 2020.

4. New Zealand Government. New Zealand COVID-19 Alert Levels Summary. Unite against COVID-19; 2020 Available from: https://covid19.govt.nz/assets/resources/tables/COVID-19-alert-levels-detailed.pdf]

5. Fouda A, Mahmoudi N, Moy N, Paolucci F. The COVID-19 pandemic in Greece, Iceland, New Zealand, and Singapore: Health Policies and Lessons Learned. Health Policy Technol. 2020.

6. Widders A, Broom A, Broom J. SARS-CoV-2: The viral shedding vs infectivity dilemma. Infection, disease & health. 2020;25(3):210-5.

7. Walsh K, Jordan K, Clyne B, et al. SARS-CoV-2 detection, viral load and infectivity over the course of an infection. J. Infection. 2020;81(3):357-71.

8. Lu J, Peng J, Xiong Q, et al. Clinical, immunological and virological characterization of COVID-19 patients that test re-positive for SARS-CoV-2 by RT-PCR. EBioMedicine. 2020;59:102960.

For the PDF of this article,
contact nzmj@nzma.org.nz

View Article PDF

We report the earliest known cluster of SARS-CoV-2 infection so far reported, which occurred in New Zealand in late February 2020. The cluster includes one confirmed and five probable cases.

The cluster was identified while investigating a weak positive nasopharyngeal swab (NPS) polymerase chain reaction (PCR) test that was returned by a male in his 60s in September 2020. The PCR result, combined with a clear clinical and epidemiological history of a COVID-19 like illness in late February 2020, prompted serological testing. SARS-CoV-2 IgG antibodies were detected and supported historical infection. Serology was also reactive for five close contacts who had also experienced a COVID-19 like illness in February 2020.

Combined case histories and investigations suggest that this local cluster was import related, with the index case identified as a family member visiting from Italy in February. Case investigation also suggests this cluster was active in New Zealand prior to any previously documented local cases, indicating that SARS-CoV-2 was present and local transmission was occurring earlier than initially suspected. A weak positive PCR result, six months after acute infection, supports international evidence that SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection, and that this is not necessarily indicative of infectivity.

Case presentation

In early September 2020, a weak positive NPS PCR result (GeneXpert Xpert® Xpress SARS-CoV-2, Cepheid, Sunnyvale, Ca, USA: E gene target CT 40.5; N2 gene 38.2) was notified to the Waikato Public Health Unit.  The male in his 60s presented for testing due to symptoms of sore throat, cough and coryza. The case interviewer was unable to identify a potential source for acute SARS-2-CoV infection. The patient did not meet any of the Higher Index of Suspicion Criteria (criteria that could indicate increased risk of exposure), including no contact with recent COVID-19 confirmed cases (or their close contacts). There was no history of exposure to locations of interest connected to the August Auckland cluster, which was active at the time.1 The case indicated that he suspected infection with SARS-CoV-2 several months earlier.

A family member and close contact of the case had arrived in New Zealand from Italy (Lombardy region) on February 23. This person became unwell shortly after arrival and presented to primary care on February 25 with a flu-like illness that included muscle aches, cough, coryza, sore throat and fever. The individual did not meet the New Zealand Ministry of Health suspected COVID-19 case definition at the time and was not eligible for testing. The individual was advised to follow standard public health advice for ‘flu-like illness’, which included to self-isolate until symptoms had resolved. Over the following four days, six household contacts became unwell with a similar flu-like illness—they followed the same precautions, self-isolating until symptoms had resolved. No one required medical attention.

The individual returned to Italy in mid-June and had SARS-CoV-2 PCR testing and serology completed shortly after. The PCR test was negative; however, the serology (Total IgG/IgM by ECLIA, I.R.C.C.S Ospedale San Rafaele Milan, It) was reactive for SARS-CoV-2 antibodies, indicative of past infection.

Laboratory testing

Serial NPS (four in total) were collected from the case and PCR results were unchanged over nine days, with GeneXpert Ct values over 36 for both targets, which continues to support a past rather than an acute infection. Whole genome sequencing of the weak positive PCR result was not possible due to the low level of genetic material.

Close contacts had NPS PCR testing completed. All, including one who was symptomatic with a coryzal illness, returned negative results. Workplace close and casual contacts were offered nasopharyngeal PCR testing. No additional positive results were reported. The occupation of the case involved frequent contact with the public and, despite intensive screening for both symptomatic and asymptomatic cases in the region, no case had been detected in relation to his workplace.

The case and the five additional household contacts who reported being unwell in February returned reactive SARS-CoV-2 results on the Roche Diagnostics Elecsys total (IgG and IgM) antibody assay (Paul Austin, Auckland City Hospital). The case also had second-line testing conducted using the Euroimmun IgG specific assay and the Wantai SARS-CoV-2 Ab ELISA. This testing confirmed the presence of IgG antibodies.

Discussion

This case report describes an import-related historical case and household cluster of COVID-19 that went unidentified during the early stages of New Zealand’s COVID-19 response. Case histories and investigations suggest that this cluster was active prior to the first reported case of imported COVID-19 and the first reported import-related case of COVID-19 in New Zealand.2

It was concluded that the ‘weak positive’ PCR result returned by the male in his 60s was most likely indicative of historical infection. Risk assessment concluded it was unlikely the case was infectious during their September illness, due to the combination of the weak positive PCR result and the presence of IgG antibodies indicating immunity. The case remained off work and isolated at home while unwell in September. No additional cases of COVID-19 occurred as a result of this case in September.

Identification of this cluster has drawn attention to some of the early challenges faced by New Zealand during the pandemic. This includes determining an appropriate case definition at a time when clinical and epidemiological information is predominantly observational and rapidly changing. The surveillance case definition also dictated allocation of the very limited testing capacity at that time.3

The decision of the New Zealand Government to implement a full-scale, nationwide lockdown in March significantly restricted the international and national movement of New Zealanders.4 This approach saw New Zealand avoid any significant health system shock, and the virus was eliminated from within the community for 102 days.5 The identification of this household cluster, which was epidemiologically linked to a region of Italy that subsequently became a region of international concern, provides evidence that undetected local transmission of SARS-CoV-2 was occurring from at least late February 2020. This finding offers additional evidence that supporting the New Zealand lockdown action and following public health advice for any influenza like illness were effective strategies in reducing transmission, from both identified cases and unrecognised clusters, to the point of elimination.

The finding of a weak positive PCR result 201 days (more than six months) after acute infection indicates SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection. Studies to date suggest that the presence of SARS-CoV-2 viral RNA on a PCR test does not necessarily correlate with infectivity.6–8 We recommend the use of serology coupled with repeat PCR to determine the ‘age’ of the infection, and thus for use as a predictor of infectivity.

Summary

Abstract

We report the earliest known cluster of SARS-CoV-2 infection so far reported, which occurred in New Zealand in late February 2020. The cluster includes one confirmed and five probable cases.

The cluster was identified while investigating a weak positive nasopharyngeal swab (NPS) polymerase chain reaction (PCR) test that was returned by a male in his 60s in September 2020. The PCR result, combined with a clear clinical and epidemiological history of a COVID-19 like illness in late February 2020, prompted serological testing. SARS-CoV-2 IgG antibodies were detected and supported historical infection. Serology was also reactive for five close contacts who had also experienced a COVID-19 like illness in February 2020.

Combined case histories and investigations suggest that this local cluster was import related, with the index case identified as a family member visiting from Italy in February. Case investigation also suggests this cluster was active in New Zealand prior to any previously documented local cases, indicating that SARS-CoV-2 was present and local transmission was occurring earlier than initially suspected. A weak positive PCR result, six months after acute infection, supports international evidence that SARS-CoV-2 genetic material can be detected for several months after initial COVID-19 infection, and that this is not necessarily indicative of infectivity.

Aim

Method

Results

Conclusion

Author Information

Dr Elizabeth Becker: Public Health Medicine Registrar, Public Health Unit, Waikato District Health Board. Dr Richard Vipond: Public Health Medicine Specialist and Medical Officer of Health, Clinical Director Waikato PHU COVID-19 response; Public Health Unit, Waikato District Health Board. Dr Chris Mansell: Clinical Microbiologist, Waikato District Health Board.

Acknowledgements

Dr Geoffrey Cramp: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Marianne Dowsett: Public Health Medicine Specialist, Public Health Unit, Waikato District Health Board. Dr Richard Hoskins: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Richard Wall: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Dr Felicity Dumble: Public Health Medicine Specialist and Medical Officer of Health, Public Health Unit, Waikato District Health Board. Bevan Clayton-Smith: Service Director Public Health, Waikato District Health Board.

Correspondence

Dr Elizabeth Becker: Public Health Medicine Registrar, Public Health Unit, Waikato District Health Board, Private bag 3200, Hamilton, 3204; Dr Richard Vipond, Public Health Medicine Specialist and Medical Officer of Health, Clinical Director Waikato PHU COVID-19 response; Public Health Unit, Waikato District Health Board, Private Bag 3200, Hamilton, 3204

Correspondence Email

elizabeth.becker@waikatodhb.health.nz, richard.vipond@waikatodhb.health.nz

Competing Interests

Nil.

1. Ministry of Health. COVID-19 - Significant clusters: Ministry of Health; 2020 [Available from: https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-current-situation/covid-19-current-cases/covid-19-significant-clusters]

2. Jefferies S, French N, Gilkison C, et al. COVID-19 in New Zealand and the impact of the national response: a descriptive epidemiological study. Lancet Public Health. 2020.

3. Cameron B. Captaining a team of 5 million: New Zealand Beats Back COVID-19, March-June 2020. Princeton School of Public and International Affairs; 2020.

4. New Zealand Government. New Zealand COVID-19 Alert Levels Summary. Unite against COVID-19; 2020 Available from: https://covid19.govt.nz/assets/resources/tables/COVID-19-alert-levels-detailed.pdf]

5. Fouda A, Mahmoudi N, Moy N, Paolucci F. The COVID-19 pandemic in Greece, Iceland, New Zealand, and Singapore: Health Policies and Lessons Learned. Health Policy Technol. 2020.

6. Widders A, Broom A, Broom J. SARS-CoV-2: The viral shedding vs infectivity dilemma. Infection, disease & health. 2020;25(3):210-5.

7. Walsh K, Jordan K, Clyne B, et al. SARS-CoV-2 detection, viral load and infectivity over the course of an infection. J. Infection. 2020;81(3):357-71.

8. Lu J, Peng J, Xiong Q, et al. Clinical, immunological and virological characterization of COVID-19 patients that test re-positive for SARS-CoV-2 by RT-PCR. EBioMedicine. 2020;59:102960.

Contact diana@nzma.org.nz
for the PDF of this article

Subscriber Content

The full contents of this pages only available to subscribers.

LOGINSUBSCRIBE