Floors Have Been Flooding From The Toilet So All Sewage

Floors have been flooding from the toilet so all sewage runs thru floor boards & both bedrooms. Landlord refuses to fix . i have had 3 lung infections & now burning fevers off & on & breaking out with red bumps they come up like red pimples then turn into sores roommate having same symptoms less lung infections instead her asthma has worsened. We cant move due to lease & finances what are these things & how or what can we do to get rid of them & stop it from coming back please.