Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Dec:10:100160.
doi: 10.1016/j.onehlt.2020.100160. Epub 2020 Aug 22.

Impact of mitigating interventions and temperature on the instantaneous reproduction number in the COVID-19 pandemic among 30 US metropolitan areas

Xinhua Yu  1
Affiliations

Impact of mitigating interventions and temperature on the instantaneous reproduction number in the COVID-19 pandemic among 30 US metropolitan areas

Xinhua Yu. One Health. 2020 Dec.

Abstract

Background: After more than six months into the coronavirus disease (COVID-19) pandemic, as of August 10, 2020, over 734,664 people had died worldwide. The current study aims to evaluate how mitigating interventions affected the epidemic process in the 30 largest metropolitan areas in the US and whether temperature played a role in the epidemic process.

Methods: Publicly available data for the time series of COVID-19 cases and deaths and weather were analyzed at the metropolitan level. The time-varying reproductive numbers (Rt) based on retrospective moving average were used to explore the trends. Student t-tests were used to compare temperature and peak Rt cross-sectionally.

Results: We found that virus transmissibility, measured by instantaneous reproduction number (Rt), had declined since the end of March for all areas and almost all of them reached a Rt of 1 or below after April 15, 2020. The timing of the main decline was concurrent with the implementation of mitigating interventions. However, the Rts remained around 1 for most areas since then and there were some small and short rebounds in some areas, suggesting a persistent epidemic in those areas when interventions were relaxed. Cities with warm temperature also tended to have a lower peak Rt than that of cities with cold temperature. However, they were not statistically significant and large geographic variations existed.

Conclusions: Aggressive interventions might have mitigated the current pandemic of COVID-19, while temperature might have weak effects on the virus transmission. We may need to prepare for a possible return of the coronavirus outbreak.

Keywords: COVID-19 epidemic; Mitigating intervention; Reproduction number; Temperature; Virus transmissibility.

PubMed Disclaimer

Conflict of interest statement

In this study, the author has no financial and conflict of interest to disclose. The ethics approval was exempted for this study, as no human subjects were involved, and all data were publicly available. The statistical codes and data will be available online (https://tinyurl.com/ybhdcjqu).

Figures

Fig. 1
Fig. 1
a-d: Time trends of instantaneous reproduction number for 30 US largest metropolitan areas.
Fig. 2
Fig. 2
Association between maximal reproduction number and 7-day average temperature among US 30 metropolitan areas.
Appendix Fig. 1
Appendix Fig. 1
a – d, Declining trend of instantaneous reproduction number over time after the peak of epidemic, US 30 metropolitan areas.
Appendix Fig. 2
Appendix Fig. 2
a-b: Variations of instantaneous reproduction numbers across 30 US metropolitan areas.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Zhu N., Zhang D., Wang W., Li X., Yang B., Song J. A novel coronavirus from patients with pneumonia in China, 2019. N. Engl. J. Med. 2020;382(8):727–733. - PMC - PubMed
    1. Center P.R. Most Americans Say Coronavirus Outbreak Has Impacted Their Lives. 2020. https://www.pewsocialtrends.org/2020/03/30/most-americans-say-coronaviru... March [cited 2020 June 18]; Available from.
    1. Peiris J.S., Yuen K.Y., Osterhaus A.D., Stohr K. The severe acute respiratory syndrome. N. Engl. J. Med. 2003;349(25):2431–2441. - PubMed
    1. Li Q., Guan X., Wu P., Wang X., Zhou L., Tong Y. Early transmission dynamics in Wuhan, China, of novel coronavirus-infected pneumonia. N. Engl. J. Med. 2020;382(13):1199–1207. - PMC - PubMed
    1. Fraser C., Riley S., Anderson R.M., Ferguson N.M. Factors that make an infectious disease outbreak controllable. Proc. Natl. Acad. Sci. U. S. A. 2004;101(16):6146–6151. - PMC - PubMed