An outbreak of clusters of viral pneumonia due to a novel coronavirus (2019-nCoV/SARS-CoV-2) happened in Wuhan, Hubei Province in China in December 2019. Since the outbreak, several groups reported estimated R 0 of Coronavirus Disease 2019 (COVID-19) and generated valuable prediction for the early phase of this outbreak. After implementation of strict prevention and control measures in China, new estimation is needed. An infectious disease dynamics SEIR (Susceptible, Exposed, Infectious, and Removed) model was applied to estimate the epidemic trend in Wuhan, China under two assumptions of R t . In the first assumption, R t was assumed to maintain over 1. The estimated number of infections would continue to increase throughout February without any indication of dropping with R t = 1.9, 2.6, or 3.1. The number of infections would reach 11,044, 70,258, and 227,989, respectively, by 29 February 2020. In the second assumption, R t was assumed to gradually decrease at different phases from high level of transmission (R t = 3.1, 2.6, and 1.9) to below 1 (R t = 0.9 or 0.5) owing to increasingly implemented public health intervention. Several phases were divided by the dates when various levels of prevention and control measures were taken in effect in Wuhan. The estimated number of infections would reach the peak in late February, which is 58,077-84,520 or 55,869-81,393. Whether or not the peak of the number of infections would occur in February 2020 may be an important index for evaluating the sufficiency of the current measures taken in China. Regardless of the occurrence of the peak, the currently strict measures in Wuhan should be continuously implemented and necessary strict public health measures should be applied in other locations in China with high number of COVID-19 cases, in order to reduce R t to an ideal level and control the infection.

An outbreak of clusters of viral pneumonia due to a novel coronavirus (2019-nCoV / SARS-

The world must act fast to contain wider international spread of the epidemic of COVID-19 now. The unprecedented public health efforts in China have contained the spread of this new virus. Measures taken in China are currently proven to reduce human-to-human transmission successfully. We summarized the effective intervention and prevention measures in the fields of public health response, clinical management, and research development in China, which may provide vital lessons for the global response. It is really important to take collaborative actions now to save more lives from the pandemic of COVID-19.

The coronavirus disease 2019 (COVID-19) has become a life-threatening pandemic. The epidemic trends in different countries vary considerably due to different policy-making and resources mobilization. We calculated basic reproduction number (R 0) and the time-varying estimate of the effective reproductive number (R t) of COVID-19 by using the maximum likelihood method and the sequential Bayesian method, respectively. European and North American countries possessed higher R 0 and unsteady R t fluctuations, whereas some heavily affected Asian countries showed relatively low R 0 and declining R t now. The numbers of patients in Africa and Latin America are still low, but the potential risk of huge outbreaks cannot be ignored. Three scenarios were then simulated, generating distinct outcomes by using SEIR (susceptible, exposed, infectious, and removed) model. First, evidence-based prompt responses yield lower transmission rate followed by decreasing R t. Second, implementation of effective control policies at a relatively late stage, in spite of huge casualties at early phase, can still achieve containment and mitigation. Third, wisely taking advantage of the time-window for developing countries in Africa and Latin America to adopt adequate measures can save more people's life. Our mathematical modeling provides evidence for international communities to develop sound design of containment and mitigation policies for COVID-19.

Background High prevalence and strong relationships among suicidal ideation, Internet gaming disorder (IGD), insomnia, and depression have been reported for adolescents worldwide, but the mechanism underlying these psychological problems remains unclear. This cross-sectional study explored the mediating effect of insomnia and depression on the association between IGD and suicidal ideation. Methods Participants were 1066 adolescents (median age = 13.0 years) with Internet games exposure in the previous 12 months from junior high schools in Shanghai, China. Questionnaire measures of suicidal ideation, IGD, insomnia, depressive symptoms, and background characteristics were obtained. Path analysis was conducted to test the multiple mediating roles of insomnia and depression. Results Suicidal ideation, IGD, insomnia, and depression prevalence was 27.2, 13.6, 9.2, and 17.0%, respectively. A serial multiple mediation model was generated. The mediation effect of insomnia and depression on the pathway from IGD to suicidal ideation was 45.5% (direct effect: standardized estimate [Std. estimate] = 0.186; total indirect effect: Std. estimate = 0.155). The association between IGD and depression was partially mediated by insomnia (direct effect: Std. estimate = 0.211; indirect effect: Std. estimate = 0.135). The proposed model fit the data well. Conclusions Insomnia and depression may serially mediate the association between IGD and suicidal ideation. IGD was positively associated with insomnia, then with depression, which in turn positively contributed to suicidal ideation. We suggest greater monitoring of Internet use and prevention of insomnia and depression to mitigate the risk of suicidal ideation among Chinese adolescents.