COVID-19

Time-varying Reproductive Rates for SARS-CoV-2 and its Implications as a Means of Disease Surveillance on Lockdown Restrictions

Toraih, Eman A. MD, PhD∗,†; Hussein, Mohammad H. MD∗; Elshazli, Rami M. PhD‡; Fawzy, Manal S. MD, PhD§,||; Houghton, August BS; Tatum, Danielle PhD#; Killackey, Mary MD∗; Kandil, Emad MD, MBA, FACS, FACE∗∗; Duchesne, Juan MD††

Author Information

∗Department of Surgery, Tulane University, School of Medicine, New Orleans, Louisiana

†Genetics Unit, Department of Histology and Cell Biology, Faculty of Medicine, Suez Canal University, Ismailia, Egypt

‡Department of Biochemistry and Molecular Genetics, Faculty of Physical Therapy, Horus University - Egypt, New Damietta, Egypt

§Department of Medical Biochemistry and Molecular Biology, Faculty of Medicine, Suez Canal University, Ismailia, Egypt

||Department of Biochemistry, College of Medicine, Northern Border University, Arar, KSA

Tulane University School of Medicine, New Orleans, Louisiana

#Academic Research Director, Our Lady of the Lake Regional Medical Center, Baton Rouge, Louisiana

∗∗Division of Endocrine and Oncologic Surgery, Department of Surgery, Tulane University, School of Medicine, New Orleans, Louisiana

††Trauma/Acute Care and Critical Care, Department of Surgery, Tulane University, School of Medicine, New Orleans, Louisiana, USA.

[email protected], [email protected].

Author contribution: MH, ET, RE, MF, JD designed the study. MH, ET, RE performed all data analyses and created the table and figure. MH, ET, RE, MF, JD contributed to data interpretation. ET, RE, AH, DT, MF wrote the first draft. ET drafted the final manuscript. All authors critically reviewed and approved the final version of the manuscript.

None of the authors have any funding regarding this publication.

The authors declare no conflict of interests.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.annalsofsurgery.com).

Annals of Surgery 273(1):p 28-33, January 2021. | DOI: 10.1097/SLA.0000000000004590

Abstract

Objective: 

To quantify the time-varying reproductive rates for SARS-CoV-2 and its implication in Louisiana.

Summary of Background Data: 

Basic reproductive number (R0) and effective reproductive number (Re or Rt) are 2 measures of the ability of an infectious agent to spread in the environment. They differ in that R0 assumes zero immunity in the population, while Re or Rt accounts for change over time. Reproductive number modeling is influenced by several factors, including serial interval, the time between the onset of symptoms in an infector, and a secondary case. Quantification of the ability of a pathogen to spread is essential in guiding policy.

Methods: 

Here, we construct epidemic curves and calculate daily Rt values for the state of Louisiana and each of its 9 regions.

Results: 

Our results demonstrated variation over both time and geography in calculated R0 and Rt values. Generally, as time has progressed, predicted R0 and Rt values have decreased. In Louisiana, mean Rt was calculated at 3.07 in March and 0.82 by May. A reproductive number less than one is important as it indicates infectious spread will decline with time. The most recent finding of mean Rt = 0.82 is important. It stands in stark contrast to the situation in April when New Orleans, Louisiana, had the highest per capita coronavirus mortality rate in the United States – twice that of New York City and 4 times the rate in Seattle.

Conclusion: 

As locations around the world begin to lift restrictions, monitoring of infectious spread will be essential.

Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.

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