Sewage contamination caused by floor drain overflows or mainline backflows (sewer backups) are perhaps the most hazardous of all property damage.  Raw, gorssly unsanitary sewage can carry a host of pathogenic agents ranging from gram negative bacteria to viruses to parasites.  Extreme caution and care should be taken to protect building occupants and avoid cross contamination of other parts of the structure.  As quickly as possible, sewage remediation, decontamination and cleaning should be performed.