How hygienic is it without a bag?

Hygienic emptying. In contrast to other bagless systems, this method consistently separates the coarse dirt from the fine dust. This fine dust is then collected in a separate container with the help of the Gore® CleanStream® fine dust filter. This reduces the unsettling of fine dust to a minimum when emptying the container.
Gore® CleanStream® fine dust filter
The innovative principle of separating coarse soiling into a transparent dust container and fine dust into a different filter container enables especially hygienic emptying of the Blizzard. When compared to other bagless systems, the Miele Blizzard excels with significantly less fine dust escaping during emptying.
The dust container can be easily removed from the appliance by pulling the handle in an upward motion. With one click on the “empty” button, the container opens and all the dust drops into the bin.
Unique sensors monitor the Gore® CleanStream® fine dust filter. The ComfortClean function cleans the fine dust filter automatically as needed. After several seconds, the Blizzard CX1 is ready for use again and keeps vacuuming powerfully.
Exhaust filter
The exhaust filter in the Miele Blizzard CX1 saves time and lifecycle costs. It is absolutely maintenance-free and of such high quality that it lasts for the entire life of the appliance. It never needs to be changed or cleaned.
Hygiene lifetime filter
The Hygiene lifetime filter features very high dust retention capacity and collects 99.98% of all fine particles*. This is the type of hygienic cleanliness that you want for your home. 
HEPA* AirClean lifetime filter
Thanks to the HEPA* HEPA 13 lifetime filter, even the smallest particles such as fine dust and allergens are retained up to 99.999%* by the system. This excellent filtration performance was confirmed by the medical organization, “Allergy UK”, and certified as suitable for those with allergies. The Miele Blizzard CX1 has been given the quality “seal of approval” for its powerful overall dust retention capacity.
According to EN 60312-1According to EN 1822/2011 Figures as examples for showing the product benefit