If that was attributed to the opening of casino, then there is a reason for the casino to be close again, but if not, I doubt the government would close the casinos as they are generating funds for taxes.
I haven't heard about any COVID 19 clusters in either in Las Vegas or in the neighboring counties which are directly linked to any of the casinos that have re-opened. And therefore I would rather blame the lifting of the lockdown measures for the recent spike in new infections. No proof exist to specifically blame the casinos for the rise in Coronavirus cases, at least in the Las Vegas region.