Forecasting Confirmed Cases, Deaths, and Recoveries from COVID-19 in China during the Early Stage

To provide a theoretical basis for the prevention and control of COVID-19 in China, conﬁrmed cases, deaths, and recoveries from COVID-19 in China were predicted using a fractional grey model. The results indicated that the grey model has high forecasting accuracy in the prediction of disease spread.


Introduction
is disease can cause severe fever and, in the worst cases, acute respiratory failure syndrome [1].
ere were 1016 recorded deaths from this outbreak as of February 10, 2020, in China. It has also spread across other countries, starting with Japan and then Australia, France, and the United States. e SARS-CoV-2 virus continues to evolve in alarming ways, with the spread of COVID-19, putting enormous strain on health systems around the world.
ere is no indication that China will succeed in beating COVID-19 in the short term. Accurately forecasting the epidemic tendency can provide a theoretical basis for the prevention and control of COVID-19.
Statistical methods are widely used for forecasting of epidemic diseases [2]. Traditional prediction methods often require a large number of data samples, which follow a certain typical distribution. However, because of the limited information available during the early stages of disease transmission, the spreading mechanism of COVID-19 is yet to be fully understood [3]. e grey prediction theory provides a new way to solve the systemic problems that occur in cases of limited information.
us, the grey prediction theory is more suitable for the prediction of the incidence of COVID-19 in China than other theories. e rest of the paper is arranged as follows. Section 2 introduces the forecasting model. Section 3 shows in detail the prediction results. Conclusions are drawn in Section 4.

Fractional Grey Model
Grey system theory mainly focuses on systems with incomplete or uncertain information [4]. In recent years, grey system theory has been successfully applied to the prediction of infectious diseases [5][6][7][8].
Despite the widespread outbreak of COVID-19, data on this disease in China are limited. Many methods cannot make accurate predictions if the data samples are small. For this reason, the fractional grey model (FGM(1,1)) is used to deal with the forecasting problem with limited samples [9]. e FGM(1,1) model is an optimized form of the grey prediction model. Its detailed modeling process has been described previously [9,10].

Results
In this section, the data are from the National Health Commission of the People's Republic of China (http://www. nhc.gov.cn/). e Chinese government has made every effort to fight the epidemic and has continued to release relevant data since January 21, 2020. Data released after January 21 were used to test the performance of the forecasts.
A rolling forecast approach was taken in the experiment. Here, the data of every five consecutive days were used as observations to predict the data for the next day. e mean absolute percentage error (MAPE) was used to test the performance of the model. e prediction results of the confirmed cases are presented in Table 1.
As shown in Table 1, the mean MAPE is 4.66%, which meets our expectations for accurate forecasting. e FGM(1,1) model only needs five consecutive days of data to predict the next day's data. It needs very little data and follows the principle of new information priority. Even for the most uncontrollable first days of the epidemic, FGM(1,1) showed accurate prediction. Since February 28, the predicted MAPE has been less than 10%, which demonstrates the adaptability of the model. e number of deaths due to COVID-19 and the number of people who have recovered are shown in Tables 2 and 3, respectively.
As shown in Tables 2 and 3, the MAPE of the number of deaths and recoveries from COVID-19 was 2.10% and 3.61%, respectively. All the MAPE values of the prediction results were less than 10%, which means that the prediction results met the requirement of highly accurate prediction.  Mathematical Problems in Engineering erefore, we took the next step to predict the future number of confirmed, dead, and recovered cases, as shown in Table 4. e predictions show that the growth rate of the number of confirmed cases was on the decline, and the number of recoveries was on the rise. Based on the above results, we further predicted the growth rate of confirmed cases. From the existing data, the growth rate showed a straight-line downward trend, so linear regression was used for prediction. e predictive effect is shown in Figure 1. We could draw the conclusion that the inflection point would be reached around February 29, the spread of COVID-19 would be effectively controlled, and the number of people infected would not increase much.

Conclusions
e spread of COVID-19 has caused great damage to the world's health care systems, so it is very necessary to predict the spread of disease in the future. In the early stages of the outbreak, data are limited and not absolutely accurate. e FGM(1,1) model is a good choice at the early stage of disease   Mathematical Problems in Engineering transmission for the prediction of trends of this new disease. FGM(1,1) is suitable for short-term prediction of time series. Using the characteristics of fractional-order accumulation, the grey model can analyze the rules in short-term data well based on the principle of new information first. Hence, FGM(1,1) could accurately predict the number of confirmed cases, the number of deaths, and the number of recoveries.
e predicted results indicate that the spread of COVID-19 will be further suppressed in China, more people will be cured, and infection rates will fall further.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
e authors declare that there are no conflicts of interest regarding the publication of this paper.