By Seema Gupta, MD, MSPH
Clinical Assistant Professor, Department of Family and Community Health, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV
Dr. Gupta reports no financial relationships relevant to this field of study.
SYNOPSIS: After studying the association of public health interventions with the epidemiological features of the COVID-19 outbreak in Wuhan, China, the authors found nonpharmaceutical interventions, including home confinement, social distancing, centralized quarantine, cordons sanitaire, and traffic restriction, may be associated with better outbreak control.
SOURCE: Pan A, et al. Association of public health interventions with the epidemiology of the COVID-19 outbreak in Wuhan, China. JAMA 2020; Apr 10. doi: 10.1001/jama.2020.6130. [Epub ahead of print].
Soon after its detection in Wuhan, China, coronavirus disease 2019 (COVID-19) evolved into a rapidly spreading infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Single-strand RNA viruses like this one can mutate quickly, adapt to different epidemiological situations, and infect many hosts (including avian, wild and domestic mammalian species, and humans).1 SARS-CoV-2 can be transmitted between humans through aerosol droplets, direct contact, fecal-oral route, and intermediate objects from asymptomatic and symptomatic patients during the incubation period.2 Symptoms may appear two to 14 days after virus exposure. Although primarily targeting the respiratory system, the disease is characterized by dry cough, fever, diarrhea, and dyspnea in 20% to 25% of patients who do not show upper respiratory signs, such as sore throat or sneezing.3
Currently, there is no vaccine available nor any pharmaceutical agents yet clearly identified to be safe and effective at preventing or treating COVID-19.4 Therefore, there has been an undue reliance by the public health community on various nonpharmaceutical interventions (NPIs) to reduce the community-level spread of COVID-19. Such measures, such as social distancing, stay-at-home policies, travel restrictions, cancelation of schools and nonessential businesses, and wearing cloth face masks, may work to mitigate and suppress new infections. NPIs could be an important tool in combating the global pandemic until a time when researchers can develop effective preventive and therapeutic countermeasures.
In their study, Pan et al evaluated the epidemiologic outcomes following implementation of NPIs during the COVID-19 outbreak in Wuhan, China, within weeks following the disease detection. They obtained individual-level data on 32,583 laboratory-confirmed COVID-19 cases and computed standardized number of infections per day per million people, effective reproduction numbers, and the proportion of severe disease in cases from December 2019 through early March 2020.
Interestingly, this time was calculated across five periods: Dec. 8 to Jan. 9 (no intervention), Jan. 10 to Jan. 22 (heavy population movement during Chinese New Year), Jan. 23 to Feb. 1 (city-wide lockdown with home quarantine, cordons sanitaire, and traffic restriction), Feb. 2 to Feb. 16 (centralized treatment and quarantine), and Feb. 17 to March 8 (door-to-door and individual-to-individual community screening survey of all residents).
Pan et al found that the local health workers had a higher daily confirmed case rate compared with that in the general population during the entire time period: 130.5 per million people (95% confidence interval [CI], 123.9-137.2) vs. 41.5 per million people (95% CI, 41.0-41.9). However, the proportion of critical and severe cases declined continuously from 53.1% to 10.3% over the five periods. The severity risk tended to increase with age. Finally, the daily confirmed case rate per million people increased from 2.0 before Jan. 10 to 45.9 between Jan. 10 and Jan. 22 and to 162.6 between Jan. 23 and Feb. 1. The rate then declined to 77.9 between Feb. 2 and Feb. 16, and to 17.2 after Feb. 16. Overall, Pan et al noted the series of multifaceted NPIs adopted was associated with improved better virus control in Wuhan.
The basic reproduction number (R0) is the number of cases expected to occur on average in a homogeneous population when a single individual is infected, when everyone is susceptible at the start of the epidemic, before widespread immunity starts to develop, and before anyone attempts immunization.
However, R0 cannot account for the time-varying nature of an epidemic. Thus, investigators may substitute a time-varying effective reproductive number (Rt) to provide more information because it tracks the subsequent evolution of transmission. If Rt is below 1, the epidemic eventually peters out. Above 1, it will grow — possibly exponentially.
In any communicable disease outbreak, it is critical to interrupt the chain of transmission by reducing the average number of cases caused by each infected individual over their infectious period, and bring the Rt to lower than 1. Pan et al provided an impressive account of the association between NPIs employed (especially travel restrictions and home quarantine) and lowering Rt to less than 1 in the early days of the Wuhan outbreak.
There are two main lessons to be learned from this study. First, we should sharpen our focus to better understand which NPI tactics produce the most return on investment when it comes to breaking the infectious cycle of the pandemic. Then, we should apply those methods as states and communities re-open across the nation.
The economic and social impact caused by widespread lockdowns are severe. A much more targeted approach may allow a successful control of the pandemic without recrudescence of infections. Second, we must enhance access to real-time data in the United States for those who are infected as well as those who need to undergo further testing, surveillance, and/or quarantine.5
There may be an extended period before a vaccine and/or effective pharmacotherapy is widely available. Evidence-based, focused NPIs, paired with a national, robust, real-time surveillance system, may just buy enough time to mitigate the current COVID-19 pandemic wave.
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