Epidemics in the past have also led to sharp pull-backs in the markets. Over the long-term, however, the stock market has weathered past epidemics. The below chart looks at the historical returns of the S&P 500 Index during multiple epidemics over the last 40 years. Over the 6 and 12 month periods following an epidemic, the S&P 500 performance has, on average, been positive.