Mumbai witnessed a sudden one-day spike in Covid-19 cases yesterday with the city recording 85 new cases as against 34 the previous day. The BMC said all the cases were asymptomatic. The cumulative tally of cases now stands at 10,58,88.<br />'' <br />''However, there were no deaths reported in the metropolis, thereby leaving the cumulative toll tally unchanged at 19,562. Meanwhile, Union Health Secretary Rajesh Bhushan has written a letter to the state government expressing concern over the spike in Covid cases.