Markets are subjected to both endogenous and exogenous risks that have caused disruptions to financial and economic markets around the globe, leading eventually to fast stock market declines. In the past, markets have recovered after any economic disruption. On this basis, we focus on the outbreak of COVID-19 as a case study of an exogenous risk and analyze its impact on the Standard and Poor’s 500 (S&P500) index. We assumed that the S&P500 index reaches a minimum before rising again in the not-too-distant future. Here we present a forecast model of the S&P500 index based on the breaking news and publicly available information. We assumed that the biggest fall of the S&P500 during the COVID-19 outbreak will occur when the largest daily number of deaths was confirmed. We inferred that the peak number of deaths occurs 2-months since the first confirmed case was reported in the USA based on previous COVID-19 situation reports from other countries. We also compare the S&P500 and the DAX market dynamics around the COVID-19 crisis as well as other previous crises, demonstrating that the impact of market news is highly consistent across these multiple market crises. The forecast is a projection of a prediction with stochastic fluctuations described by $q$-gaussian diffusion process with three spatio-temporal regimes. Our forecast was made on the premise that any market response can be decomposed into an overall deterministic trend and a stochastic term. The prediction was based on the deterministic part and for this case study is approximated by the extrapolation of the S&P500 data trend in the initial stages of the outbreak. The stochastic fluctuations have the same structure as the one derived from the past 24 years. A reasonable forecast was achieved with 85% of accuracy.

市场承受着内源性风险和外源性风险，这些风险已导致全球金融和经济市场中断，最终导致股市快速下跌。过去，市场在遭受任何经济动荡后已经恢复。在此基础上，我们将COVID-19的爆发作为外生风险的案例研究，并分析其对标准普尔500（S＆P500）指数的影响。我们假设标准普尔500指数在不久的将来再次上升之前达到最小值。在这里，我们根据突发新闻和公开可用的信息，提出了S＆P500指数的预测模型。我们认为，当确认每天死亡人数最多时，S＆P500在COVID-19爆发期间的最大跌幅将发生。根据其他国家先前的COVID-19情况报告，我们推断自美国报告第一例确诊病例以来，死亡高峰出现在两个月之内。我们还比较了围绕COVID-19危机以及之前的其他危机的S＆P500和DAX市场动态，这表明市场新闻在这些多重市场危机中的影响高度一致。预测是具有以下预测的随机波动的预测的投影$q$-高斯扩散过程，具有三种时空模式。我们的预测是在任何市场反应都可以分解为总体确定性趋势和随机术语的前提下进行的。预测基于确定性部分，在本案例中，通过对爆发初期S＆P500数据趋势的外推进行近似。随机波动的结构与过去24年的波动相同。达到了85％的准确预测率。