The instinct is understandable. There is water on the basement floor, it came up through a drain, and the plan is rubber gloves, a mop, a shop vac, and a jug of bleach before anybody else has to look at it.
Two things go wrong with that plan, and neither one is squeamishness.
The exposure problem
The first is exposure. Contact with raw sewage is treated as a recognized hazard in workplace regulation, which is why crews that do this professionally wear boots, gauntlet gloves, eye protection, a suit that seals, and respiratory protection where aerosols are a factor. Dish gloves and a bandana are not a scaled down version of that. They are a different thing entirely.
Shop vacs and mopping create aerosols. That is the part nobody thinks about. Agitating contaminated water puts it into the air of a closed basement you are standing in without a respirator.
The containment problem
The second problem is containment, and it is the one that ruins houses.
Contaminated water spreads by wicking, not just by flowing. It climbs drywall from the bottom edge. It travels under vinyl and laminate, along the underside of subfloor, into the sill plate and the bottom of the wall cavity. Anyone working without containment tracks it into rooms that were clean, and now the affected area is larger than it was before cleanup started.
Bleach does not solve either problem. It is a surface disinfectant, it does not penetrate porous material, and it does nothing about water that already moved into a wall cavity. Sprayed on drywall that soaked up sewage, it produces a wall that smells like bleach and is still contaminated behind the paper.
What the actual sequence looks like
Here is what the actual sequence looks like, which is why sewage backup cleanup is a scoped job rather than a chore.
Stop adding to it. No flushing, no laundry, no dishwasher. Every fixture in the house feeds the same line.
Establish the category of water and how far it traveled, including behind walls and into ductwork if a floor register was in its path.
Contain the area before removal starts, so the work does not carry contamination into dry parts of the house.
Extract with equipment built for solids and contaminated water.
Remove the porous material that absorbed it. Carpet and pad, affected drywall, sometimes subfloor. Porous material that soaked up contaminated water is removed rather than cleaned back to safe.
Clean and treat what remains, then dry the structure with monitoring instead of guesswork, and verify with meter readings before anything gets closed up.
Document all of it, because the insurance conversation depends on it.
On the exposure point, the regulator is explicit. Federal workplace safety guidance states that contact with raw sewage and wastewater poses a number of health hazards and requires employers to evaluate exposure and provide appropriate protective equipment. That standard exists because people who do this daily get sick without it. A homeowner doing it once has the same biology and less gear.
Check whether you are covered
One more thing, and it is the question people ask second, right after how bad is it. Check whether you are actually covered. Standard homeowner policies commonly exclude sewer and drain backup, alongside flood and gradual leaks. It is sold as a separate endorsement, and plenty of people learn they never bought it while standing in the loss.
If your home ties into a municipal system, or sits below street level, ask a plumber about a backflow prevention assembly. It is the one piece of hardware that addresses the cause rather than the aftermath, and it almost never comes up until after the second backup.
What you can do while you wait
The homeowner list is short. Keep people and pets out. Shut off electricity to the area if the panel can be reached without standing in water. Photograph the scene before anything is touched. Stop using water. Open a window if the space allows it.
That is the list. Everything past it is an equipment and exposure problem, and the version where somebody mops up and runs a box fan is the version that gets a second call two weeks later, when the smell comes back and the wall is soft.