Primus
Originally begun in Beligum, Primus is now a world-wide producer/seller of commercial laundry equipment.
One assumes laundry workers shown above know how much to load machines for rated capacity. Remember despite their top opening the washers are H-Axis so a good amount of the wash will compact down.
As for sanitation,disenfection etc... that is all carried out by a mixture of chemicals, wash cycles, and temperature. Though one assumes laundry contaminated with serious pathogens (such as from an isolation room or patient with serious disease) would be separated out for special treatment.
Most all commercial laundries, and we're talking everything from service washes at local laundrettes to large scale operations with tunnel washers, rarely if ever pre-treat for stains. It is just too labour intensive which would cut down into profits and or cause a price increase. Rather wash programs are tailored to meet common stains and or special cycles for those most often found.
For instance operating room linens might have a cycle designed to shift blood. Table linens for protein, starch and other food/beverage stains. Kitchen linens grease/fats/oils, etc.
Most common formula for dealing with blood in commercial laundries, going back ages has been to have a first wash in warm water with alkaline substance. However today's modern enzyme and oxygen bleach containing detergents will do an excellent job of shifting most blood and other stains for that matter if the cycles are properly designed and product dosed correctly.
Finally as for the final laundry results concerning sanitation; if an outbreak of disease does occur nursing and or medical staff can and will quickly trace things to their source. In many hospitals it is not uncommon for "infection control" nursing and or medical staff to routinely test samples of "clean" laundry as it comes back from the wash.