Risk aversion returned to financial markets again on Thursday, with concerns over a potential second wave of the COVID-19 virus leading to a violent sell-off in stocks and high risk currencies.US equity markets experienced their biggest daily drop since the height of the market panic in March, with the S&P 500 index tumbling by over 6% for the day. The reaction in the currency markets was not quite as aggressive, although we did witness sell-offs in high beta currencies such as the Australian and New Zealand dollars and an appreciation in the safe-havens.Fears regarding an increase in virus infection in a handful of US states was largely to blame for the decreased appetite for risk. Florida, Texas and Arizona all registered their highest number of new daily cases of the virus, with a total of 19 states still seeing an upward trend in reported cases right at a time when restrictions are beginning to be eased. Ongoing widespread protests in the US and beyond provide further reason for concern and have many onlookers fearing a second wave of infection that could cripple the global economic recovery.Fed Chair Jerome Powell warned over such a possibility during the central bank’s meeting on Wednesday, stating that another wave of infection could harm the US recovery and lead to an increase in joblessness. Should this uptick in new cases continue as a result of the mass gatherings in the coming days, then this trend of a strengthening dollar and deprecation in risk assets could remain the key theme in markets for a little while yet.