Introduction
The ongoing epidemic of the novel coronavirus (SARS-CoV-2) is primarily affecting mainland China and can be traced back to a cluster of severe pneumonia cases identified in Wuhan, China in December 2019 (Li et al., 2020; World Health Organization, 2020). Early cases of the disease have been linked to a live animal seafood market in Wuhan, pointing to a zoonotic origin of the epidemic. However, human-to-human transmission has driven its rapid spread with a total of 37,289 confirmed cases, including 813 deaths, in China and 302 confirmed cases imported in multiple countries as of February 9, 2020 (Chinese National Health Committee). While the early transmission potential of this novel coronavirus appeared similar to that of severe acute respiratory syndrome (SARS) (Riou & Althaus, 2020), the current tally of the epidemic has already surpassed the total cases reported for the SARS outbreaks in 2002–2003 (W. World Health Organization, 2003; Wu, Leung, & Leung, 2020; Zhang et al., 2020).
The timing and location of the outbreak facilitated the rapid transmission of the virus within a highly mobile population. The initial reporting of observed cases occurred during the traditional Chinese New Year, when the largest population movement takes place every year (Ai et al., 2020). Further, Wuhan is a highly populated city with more than 11 million residents and is connected to many cities in China through public transportation, such as buses, trains, and flights (Lai et al., 2020; Read, Bridgen, Cummings, Ho, & Jewell, 2020). In the absence of pharmaceutical interventions, rapid action was required by the Chinese government to mitigate transmission within and outside of Wuhan.
On January 23, 2020, the Chinese government implemented a strict lockdown of Wuhan, followed by several nearby cities in subsequent days; the lockdowns include temporarily suspending all public transportation and advising residents to remain at home (Du et al., 2020; Wu et al., 2020). Further, many high-speed rail stations and airports have implemented screening measures to detect travelers with a fever, specifically those traveling from Wuhan, and those with a fever are referred to public hospitals (Lai et al., 2020; Wu et al., 2020). Within hospitals, patients who fulfill clinical and epidemiological characteristics of 2019-nCoV are immediately isolated.
The number of 2019-nCoV cases in Wuhan quickly outnumbered the available number of beds in hospitals, putting a substantial burden on the healthcare system. Consequently, the government rapidly built and launched two new hospitals with capacity for 1,600 and 1,000 beds, respectively, in Wuhan in addition to the existing 132 quarantine sites with more than 12,500 beds (Steinbuch, 2020). To anticipate additional resources to combat the epidemic, mathematical and statistical modeling tools can be useful to generate timely short-term forecasts of reported cases. These predictions can include estimates of expected morbidity burden that can help guide public health officials preparing the medical care and other resources needed to confront the epidemic. Short-term forecasts can also guide the intensity and type of interventions needed to mitigate an epidemic (Funk, Camacho, Kucharski, Eggo, & Edmunds, 2016; Shanafelt, Jones, Lima, Perrings, & Chowell, 2017). In the absence of vaccines or antiviral drugs for 2019-nCoV, the effective implementation of nonpharmaceutical interventions, such as personal protection and social distancing, will be critical to bring the epidemic under control.
In this emerging epidemic, the epidemiological data is limited, and the epidemiological parameters needed to calibrate elaborate mechanistic transmission models are not yet fully elucidated. Real-time short-term forecasts must be based on dynamic phenomenological models that have been validated during previous outbreaks (Chowell et al., 2016; Pell, Kuang, Viboud, & Chowell, 2018)(Bürger, Chowell, & Lara-Díıaz, 2019). We employ several dynamic models to generate and assess 5, 10, and 15 day ahead forecasts of the cumulative number of confirmed cases in Hubei province, the epicenter of the epidemic, and the overall trajectory of the epidemic in China excluding the province of Hubei.