I agree with Strawman. Very unlikely they would close the market, except as a short-term circuit-breaker like they do in the US whenever there is a 7% fall. They close the market there for 15 mins I think it is on 7% falls to give everyone a chance to catch their breath and think about whether that sort of panic is justified or an over-reaction. More here: https://www.npr.org/2020/03/09/813682567/how-stock-market-circuit-breakers-work
Because the market is run via computers, there is no gathering of people where the virus could spread, so no need to close it on those grounds.