Aparoova Mandavalli has a long article in the New York Times today questioning whether family and interhousehold social gatherings are driving the extra spread in November. The data doesn't support the idea.
Instead, data from some states suggests it’s still the big places known before. Look at Colorado especially. Jails. Nursing homes. Restaurants and bars weren’t even as big.
But there is more virus everywhere.
One biggie: in many places the air is drier, and that could make the virus more transmissible through aerosols, like in buildings, even with masks. This hasn’t been talked about that much yet.