By and large, US Americans are in denial about a lot: the brutality of our militarism, the ecological cost of our lifestyle, the ethical vacuum where our communal heart should be. But denying the reality of a contagion is a whole ‘nother level of blindness.
History is full of infectious disease outbreaks; enough to call them regular, or even common. Repeated experience has built a body of knowledge of how to respond sensibly to such events; quarantine, isolation, and cordon sanitaires are tried-and-true methods, long proven through trial and (tragic) error. In short, we know the drill.
Not responding sensibly, then, is ignorant at best. It can also be willful stupidity or even malice, as history has also demonstrated.
In the US right now, we are witnessing some indisputably inappropriate behavior, as people gather in groups in public places to protest the social restrictions that various levels of government have been declaring.