“…The policy of isolating or cohorting patients with suspected or confirmed influenza is reinforced; application of an aerosol-generating procedure is allowed only in adequately ventilated single rooms before influenza can be excluded; all patients with respiratory infections are required to wear face masks, which are freely provided, until symptoms subside; air-conditioning units and their settings are regularly checked to avoid airflow imbalance; and HCWs are advised to use N-95 respirators, face shields, gloves, and gowns while performing aerosol-generating procedures and to receive annual influenza vaccines [2,5,8,9]. We have adopted these measures on all medical wards, because there might be similar unsuspected or "invisible" patients with influenza acting as infection sources.…”