Pathogens use the social interaction networks of their hosts for transmission to new host individuals. Social insect colonies are inherently sub-structured into foragers and nurses with the queen. Upon pathogen contact, this sub-structuring gets more pronounced, further reducing disease transmission to the queen.
Read more on the organizational immunity hypothesis and its first experimental evidence:
Stroeymeyt et al 2014 COIS
Stroeymeyt et al 2018 Science