 It is known that the growth of the pandemic spreading at its threshold is exponential  but it is not known how to quantify the success of different containment policies.
<fluency>  It is known that the growth of the pandemic spreading at its threshold is exponential  but it is not known how to quantify the success of different containment policies.
 It is known that the growth of the pandemic spreading at its threshold is exponential , but it is not known how to quantify the success of different containment policies.