The Control Disease Center (CDC) recommend wearing a face masks for flu for anybody that has already a sickness such as the flu or any other precondition. You can read more about the hku1 in our Guide.
The coronavirus oc43 is shutting down the all world with massive quarantine orders for fear to spread further the disease. Over 250,000 people worldwide have been infected already. But to avoid this number that is going to increase exponentially we could all imitate Hong kong and wear nodpod.