Version 1
: Received: 12 March 2023 / Approved: 13 March 2023 / Online: 13 March 2023 (06:31:08 CET)
How to cite:
Nikam, C.; Suraweera, W.; Fu, S.H.; Brown, P.E.; Nagelkerke, N.; Jha, P. SARS-CoV-2 Positivity and Viral Load during Three Viral Waves in Mumbai, India. Preprints2023, 2023030219. https://doi.org/10.20944/preprints202303.0219.v1
Nikam, C.; Suraweera, W.; Fu, S.H.; Brown, P.E.; Nagelkerke, N.; Jha, P. SARS-CoV-2 Positivity and Viral Load during Three Viral Waves in Mumbai, India. Preprints 2023, 2023030219. https://doi.org/10.20944/preprints202303.0219.v1
Nikam, C.; Suraweera, W.; Fu, S.H.; Brown, P.E.; Nagelkerke, N.; Jha, P. SARS-CoV-2 Positivity and Viral Load during Three Viral Waves in Mumbai, India. Preprints2023, 2023030219. https://doi.org/10.20944/preprints202303.0219.v1
APA Style
Nikam, C., Suraweera, W., Fu, S.H., Brown, P.E., Nagelkerke, N., & Jha, P. (2023). SARS-CoV-2 Positivity and Viral Load during Three Viral Waves in Mumbai, India. Preprints. https://doi.org/10.20944/preprints202303.0219.v1
Chicago/Turabian Style
Nikam, C., Nico Nagelkerke and Prabhat Jha. 2023 "SARS-CoV-2 Positivity and Viral Load during Three Viral Waves in Mumbai, India" Preprints. https://doi.org/10.20944/preprints202303.0219.v1
Abstract
Background: The SARS-CoV-2 laboratory PCR tests were generally reported only as binary positive or negative outcomes. Instead test positivity, these results contain a great deal of epidemiological information related to viral transmission patterns in populations. These transmission patterns during India’s SARS-CoV-2 viral waves remain largely undocumented. Methods: We analysed 2.7 million real-time polymerase chain reaction (PCR) testing records collected in Mumbai, a bellwether for other Indian cities. We used the inverse of cycle threshold (Ct) values to determine community-level viral load. We quantified wave-specific differences by age, sex and slum population density. Results: Overall PCR positivity was 3.4% during non-outbreak periods, rising to 23.2% and 42.8% during the Aleph (June-November 2020) and Omicron waves (January 2022), respectively, but only 9.9% during the Delta wave (March-June 2021). The community-level median Ct values fell and rose ~7-14 days prior to PCR positivity rates. Viral loads were 4-fold higher during the Delta and Omicron waves than during non-outbreak months. The Delta wave had high viral loads at older ages, in women and in areas of higher slum density. During the Omicron wave, differences in viral load by sex and for slum density had disappeared, but older adults continued to show higher viral load. Conclusions: Mumbai’s viral waves had markedly high viral loads representing an early signal of pandemic trajectory. Continue the vaccination in elderly Indians could reduce viral load in subsequent waves. Ct values are practicable monitoring tools.
Keywords
SARS-CoV-2 pandemic; PCR positivity; Aleph Delta Omicron waves; Mumbai; India
Subject
Biology and Life Sciences, Virology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received:
13 March 2023
Commenter:
Vivek Dwivedi
The commenter has declared there is no conflict of interests.
Comment:
W.r.t article, the analysis of community-level viral load using the inverse of cycle threshold (Ct) values is an innovative approach that can help in monitoring the pandemic trajectory and identifying areas of high transmission.
Also, the finding that older adults continue to show higher viral loads during the Omicron wave despite the disappearance of differences in viral load by sex and for slum density highlights the importance of targeted interventions for this vulnerable population.
Hence, need to conduct further research to explore the effectiveness of Ct values as practicable monitoring tools for viral transmission and develop protocols for their routine use in public health surveillance.
Commenter: Vivek Dwivedi
The commenter has declared there is no conflict of interests.
Also, the finding that older adults continue to show higher viral loads during the Omicron wave despite the disappearance of differences in viral load by sex and for slum density highlights the importance of targeted interventions for this vulnerable population.
Hence, need to conduct further research to explore the effectiveness of Ct values as practicable monitoring tools for viral transmission and develop protocols for their routine use in public health surveillance.