Yes, brown rats can be dangerous, though not usually in the way people picture. The real risks aren't attacks. They're diseases spread through urine, droppings and contaminated dust, occasional bites, and damage to wiring, gas lines and foundations that can start fires or cost a lot to fix. This guide covers what a brown rat is, which diseases they actually carry, whether they're aggressive, the risks to dogs and cats, and how to clean up safely.
Are brown rats dangerous? They can be. The CDC lists diseases spread directly by rodents, including leptospirosis, rat-bite fever and salmonella, and brown rats are the main carrier of Seoul hantavirus. They also gnaw electrical wires and can chew gas lines. They don't carry rabies.
Are they dangerous to touch or be near? Wild rats usually avoid people, but don't handle them, and don't sweep or vacuum their droppings, which can put germs into the air you breathe.
What Is a Brown Rat?
The brown rat (Rattus norvegicus) goes by several names: Norway rat, sewer rat, street rat, wharf rat. They're all the same animal, so "are sewer rats dangerous?" has the same answer. The University of California describes it as large and stocky, weighing 7 to 18 ounces, with a blunt muzzle, small ears and a tail shorter than its head and body. It burrows along foundations, under woodpiles and trash, and lives mostly in basements, crawl spaces and ground floors. In North Carolina it's far more common than the roof rat. See roof rats vs. Norway rats.
What Diseases Do Brown Rats Carry?
The CDC lists diseases spread directly by rodents, and the University of California names the most common rat-transmitted ones. The main ones for brown rats:
| Disease | How people get it |
|---|---|
| Leptospirosis | Contact with urine, or water and soil contaminated with it. The CDC says risk rises after hurricanes, heavy rain and flooding. |
| Rat-bite fever | Bites or scratches, or contact with infected rodents. The CDC says it "must be treated quickly, or it can cause severe illness and possibly death." |
| Salmonella and other food poisoning | Food or surfaces contaminated by droppings (University of California also names E. coli and Campylobacter). |
| Seoul hantavirus | Breathing dust from urine, droppings or nesting material. The CDC says Norway rats are the primary carrier, wild or pet. |
| Murine typhus and plague | Indirectly, through fleas that feed on rats. UC notes plague is very rarely found in rats around homes. |
The CDC lists several ways rodent diseases reach people: touching urine, droppings or saliva; breathing air contaminated with rodent waste; bites and scratches; and eating contaminated food. That's why cleanup matters as much as getting rid of the rats. For more on rodent signs, see signs you have rats in your walls.
Are Brown Rats Aggressive? Do They Bite?
Wild brown rats generally avoid people and run when they can. Bites tend to happen when a rat is cornered, trapped or handled, for example when someone tries to grab one or reaches toward a trapped rat. The CDC says anyone can get rat-bite fever from contact with rodents, and that people with pet rodents or who work with rodents are at higher risk. If you're bitten or scratched, wash the wound well and see a doctor, and mention the rat contact.
Do Brown Rats Carry Rabies?
No. The University of California says that unlike raccoons, skunks, foxes and bats, rats and mice living around buildings "do not carry or transmit rabies." A bite still needs medical attention because of rat-bite fever and infection.
Are Brown Rats Dangerous to Dogs and Cats?
- Leptospirosis. The CDC lists dogs and cats among the animals that can be infected, through contact with contaminated urine in water or soil. Ask your vet about leptospirosis vaccination, especially if your dog swims or drinks from puddles.
- Bites. A dog that catches a rat can be bitten. On Reddit (via Google search excerpts), dog owners whose dogs killed rats were advised to "get it checked at the vet" if there was any wound.
- Poisoned rats. The University of California warns that "exposure to even a single dead rodent might be enough to poison a pet" when strong rat baits are in use. Keep pets away from bait and from dead or dying rats, including ones from a neighbor's yard.
Damage and Fire Risk
The University of California lists the damage rats cause:
- Electrical wiring, which can cause sparks and fires, especially when rats are in an attic.
- Gas lines, which rats may chew, creating explosion and fire hazards.
- Foundations and slabs, which Norway rats can undermine by burrowing.
- Car wiring, a common and expensive repair.
- Insulation and stored food, which they shred and contaminate. Brown rats can gnaw soft metals like copper and lead, plus plastic and wood.
How to Clean Up After Rats Safely
The CDC says diseases are mainly spread from rodents when people breathe in contaminated air, so:
- Air the space out for 30 minutes with doors and windows open, and leave while it airs.
- Put on rubber or plastic gloves.
- Don't sweep or vacuum droppings, urine or nests.
- Spray them until very wet with an EPA-registered disinfectant or a fresh bleach solution (1.5 cups of household bleach per gallon of water), and let it soak 5 minutes or as the label says.
- Wipe up with paper towels, throw them in a covered trash can, then mop or sponge the area with disinfectant.
For dead rats, the University of California says to use gloves or a bag, never bare hands, and seal the rat in a plastic bag before putting it in the trash.
What to Do About Brown Rats
- Remove food and shelter: sealed trash and pet food, no fallen fruit, woodpiles and clutter away from the house.
- Seal entry points of 1/2 inch or more with metal materials. See rodent proofing your home.
- Trap along walls where you see droppings. See how exterminators get rid of rats.
- Call a professional if rats are in walls, the attic or crawl space, or keep coming back. Our rodent control service covers South Carolina, North Carolina and Virginia.
Key Takeaways
- Brown, Norway and sewer rats are the same species.
- The main dangers are diseases (leptospirosis, rat-bite fever, salmonella, Seoul virus) and damage to wiring and gas lines.
- They usually avoid people but can bite when cornered or handled.
- They don't carry rabies.
- Protect pets from leptospirosis, bites and poisoned rats.
- Never sweep or vacuum droppings; soak them with disinfectant first.
Frequently Asked Questions
They can be. The CDC lists diseases spread directly by rodents, including leptospirosis, rat-bite fever and salmonella, and brown (Norway) rats are the main carrier of Seoul hantavirus. Rats can also bite if cornered or handled, and they damage wiring and gas lines. They don't carry rabies.
Sewer rats are brown rats (Norway rats), so the risks are the same: diseases spread through urine, droppings and contaminated dust, possible bites if cornered or handled, and damage to wiring and foundations. Their link to sewers and drains is one reason leptospirosis risk rises after flooding.
Not usually. Wild brown rats generally avoid people and run when they can. They can bite when cornered, trapped or handled, so don't try to catch one by hand or reach toward a trapped rat.
The main ones are leptospirosis, rat-bite fever, salmonella and other food poisoning, and Seoul hantavirus, which Norway rats primarily carry. Murine typhus and plague can be spread indirectly by fleas from rats, though plague is very rarely found in rats around homes.
No. University of California guidance says rats and mice that live around buildings do not carry or transmit rabies, unlike raccoons, skunks, foxes and bats. A bite still needs medical attention because of rat-bite fever and infection.
They can be. Dogs can catch leptospirosis from urine in water or soil, get bitten when catching a rat, or be poisoned by eating a rat that ate strong rat bait. Ask your vet about leptospirosis vaccination, and keep dogs away from bait and dead rats.
Yes, if you do it the CDC way: air the room for 30 minutes, wear rubber gloves, and spray droppings and urine with disinfectant or a bleach solution until very wet before wiping them up with paper towels. Don't sweep or vacuum them, which can put germs into the air.
Look for droppings, gnaw marks and entry points, seal gaps of 1/2 inch or more with metal materials, set traps along walls where you see activity, and store food and trash in sealed containers. If rats are in the walls, attic or crawl space, call a professional.
Sources: CDC, "Rodent Control", "How to Clean Up After Rodents", "About Rat Bite Fever," "About Leptospirosis" and hantavirus guidance on Seoul virus; University of California Statewide IPM Program, "Pest Notes: Rats" (74106); NC Parks, Mammals of North Carolina; Reddit r/dogs, r/jackrussellterrier and r/DogAdvice (via Google search excerpts).
Photo credits: Zeynel Cebeci, CC BY-SA 4.0; Chuck Homler d/b/a Focus On Wildlife, CC BY-SA 4.0; via Wikimedia Commons.