Q4. Is the crosswind solution also effective against the flu?

Definitely yes. Although the flu is a myxovirus with a seasonal reproductive number R of ~1.3, it is nonetheless an enveloped virus with spike fusion proteins similar to a coronavirus and is transmitted by similar mechanisms.  Therefore this solution is very effective against the flu.  To maintain maximum efficacy, all visitors to a resident room must sign a notice instructing them how to abide by the air barrier protocol [view here in Part 3].