Epidemic dynamics of COVID-19 based on SEAIUHR model considering asymptomatic cases in Henan province, China

1 Background: New coronavirus disease (COVID-19), an infectious disease caused by 2 a type of novel coronavirus, has emerged in various countries since the end of 2019 and 3 caused a global pandemic. Many infected people went undetected because their 4 symptoms were mild or asymptomatic, but the proportion and infectivity of asymptomatic infections remained unknown. Therefore, in this paper, we analyzed the proportion and infectivity of asymptomatic cases, as we as the prevalence of COVID- 19 in Henan province. Methods: We constructed SEAIUHR model based on COVID-19 cases reported from 9 21 January to 26 February 2020 in Henan province to estimate the proportion and 10 infectivity of asymptomatic cases, as we as the change of effective reproductive number, 11 𝑅 𝑡 . At the same time, we simulated the changes of cases in different scenarios by 12 changing the time and intensity of the implementation of prevention and control 13 measures. 14 Results: The proportion of asymptomatic cases among COVID-19 infected individuals 15 was 42% and infectivity of asymptomatic cases was 10% of that symptomatic ones . The basic reproductive number 𝑅 0 2.73, and 𝑅 𝑡 dropped below 1 on 1 February under a series of measures. If measures were taken five days earlier, the number of cases 18 would be reduced by 2/3, and after 5 days the number would more than triple. Conclusions: In Henan Province, the COVID-19 epidemic spread rapidly in the early stage, and there were a large number of asymptomatic infected individuals with 21 relatively low infectivity. However, the epidemic was quickly brought under control with national measures, and the earlier measures were implemented, the better.

3 with national measures, and the earlier measures were implemented, the better.   Wuhan[7]. And some even suggested that most infections were caused 43 by undetected cases [5,8]. A significant proportion of these undetected infected 44 4 individuals were asymptomatic [7], and although they had no symptoms, their viral load 45 was comparable to that of the confirmed cases [9], making them somewhat 46 infectious [10]. 47 The fraction of asymptomatic cases is a critical epidemiological characteristic that from 5% to 80% [14]. And current study only shows that asymptomatic infected 57 individuals are less contagious than symptomatic ones, but there is no consensus on 58 how contagious they are [15,16]. Therefore, it is important to estimate the proportion 59 and infectivity of asymptomatic cases in various regions. Taking Henan province as an 60 example, we used a model-inference framework to explore the proportion and 61 infectivity of asymptomatic cases, so as to estimate the prevalence of COVID-19 and 62 evaluate the effect of prevention and control measures. The study area is located in east-central part of China (31°23′ to 36°22′ north 67 latitude, 110°21′ to 116°39′ east longitude, Fig 1), with a population of more than 96 68 million and an area of 167,000 km 2 . Most of Henan is located in the warm temperature 69 zone and has the characteristic of climate transition from plain to hills and mountains 70 from east to west.  Although the definition of COVID-19 cases has been changed several times, which 80 has greatly affected the observed epidemic curve in Wuhan[17], the change of cases in 81 Henan province has been relatively stable, and the diagnosis of all cases in this study   89 To consider asymptomatic infected individuals, we constructed the susceptible-90 exposed-asymptomatic-confirmed-unconfirmed symptomatic-hospitalized-removed 91 (SEAIUHR) model by extending the classic susceptible-exposed-infectious-removed 92 (SEIR) model to include asymptomatic cases, unconfirmed symptomatic cases who did 93 not seek medical attention or get tested for mild symptoms, and quarantined confirmed   were infectious periods of confirmed symptomatic, asymptomatic and unconfirmed 116 symptomatic cases, respectively and was the duration from hospitalization to 117 recovery or death. Assume that

Modeling the epidemic of COVID-19 in Henan province
The differential equations in the model were numerically solved using a 4 th order Then, the formula of could be expressed by the following step function: Where 0 was the transmission rate due to symptomatic infected individuals before 130 implementing measures; was the decreasing rate of transmission rate; 1 was the 131 date to start implementing measures.

132
The effective reproductive number, , could be computed as In the initial state, namely, = 0, was the basic reproductive number ( 0 ).

136
Initial states and parameters setting in the model were presented in Table 1. We 137 assumed that the initial latent population, asymptomatic infected population and  beginning of the epidemic, which was equal to the basic reproduction number ( 0 ).

188
With the implementation of measures, fell below 1 on 1 Feburary.

189
The first-level public health emergency response was implemented to COVID-19 infections would reduce by 7% and doubling that would reduce by 20% (Table 3). 202 We used model-generated synthesis outbreak in free simulation to test the model-   This study also has some limitations. Firstly, our estimate of the asymptomatic   Consent for publication 301 Not applicable.

302
Availability of data and materials 303 The dataset used in the study are available from the corresponding author on reasonable 304 request.