It multiplies rapidly within the larva until it causes death. Then the house bees cleaning out the cells probably distribute the virus to other larvae within the hive. The disease is usually limited to one or a few colonies in an apiary. No known control exists. In severe cases moving the colony or requeening may help.
Colonies usually recover from sacbrood without beekeeper aid.
Nosema apis , a small, single-celled protozoan. Nosema disease is widespread and can cause extensive losses of adult bees. There is reduced brood production in a colony affected with the disease. It is also responsible for supersedure of queens especially in colonies established from infected package bees. Colonies infected with Nosema have heavier winter losses and there is a decrease in foraging and colonies store less honey.