Rats carry and transmit more than a dozen diseases to humans through bites, urine, droppings, and the fleas and ticks they host. Some of these illnesses are mild and self-limiting, while others, like hantavirus pulmonary syndrome, carry fatality rates as high as 35 to 50%. Understanding how each disease spreads is the key to knowing your actual risk.
Leptospirosis
Leptospirosis is one of the most common rat-borne bacterial infections worldwide. The bacteria spread through the urine of infected rats and can survive in water and soil for weeks. You can become infected by wading through floodwater, touching contaminated soil, or drinking water that an infected rat has urinated in. The risk spikes after hurricanes, heavy rainfall, and flooding, when rat urine washes into standing water that people come into contact with.
Symptoms typically appear 2 to 30 days after exposure and range from mild flu-like illness (fever, headache, muscle aches) to severe complications including kidney damage, liver failure, and meningitis. The wide incubation window means people often don’t connect their illness to the exposure that caused it.
Hantavirus Pulmonary Syndrome
Hantavirus is transmitted when people breathe in tiny particles from rat urine, droppings, or saliva. This is what makes cleaning up after a rat infestation genuinely dangerous: sweeping or vacuuming droppings can launch viral particles into the air. Early symptoms look like the flu, with fever, muscle aches, and fatigue. Within days, the lungs fill with fluid and breathing becomes severely impaired.
The fatality rate for hantavirus pulmonary syndrome sits around 31 to 36% in documented U.S. cases, with some estimates as high as 50%. There is no specific antiviral treatment. Survival depends largely on early recognition and intensive supportive care. In the U.S., the deer mouse is the primary carrier, but several rat species carry hantavirus strains globally.
Rat-Bite Fever
Rat-bite fever comes from bacteria transmitted through bites, scratches, or contact with a dead rat. It can also spread through food or water contaminated with rat feces, a form sometimes called Haverhill fever that tends to cause more severe nausea and vomiting.
Symptoms usually begin 3 to 10 days after a bite and start with fever, chills, headache, muscle pain, and vomiting. A red or purple rash develops on the hands and feet roughly 2 to 4 days after the fever starts. About half of patients go on to develop painful joint swelling. Left untreated, the infection can progress to abscesses, pneumonia, hepatitis, or heart inflammation. Heart involvement carries the highest risk of death, though this complication is rare. Rat-bite fever responds well to antibiotics when caught early.
Plague
Plague, the disease caused by the bacterium Yersinia pestis, still exists today and cycles naturally among wild rodents and their fleas. Rats don’t transmit plague directly to people. Instead, fleas feeding on infected rats pick up the bacteria, and when the rat dies, those hungry fleas jump to the nearest warm-blooded host, including humans. A flea bite can cause bubonic plague (swollen lymph nodes) or septicemic plague (bloodstream infection).
The last urban rat-associated plague outbreak in the U.S. occurred in Los Angeles in 1924 to 1925. Today, a handful of human plague cases still occur each year in the rural western United States, primarily from contact with wild rodents and their fleas rather than urban rats.
Lymphocytic Choriomeningitis (LCMV)
LCMV is a virus carried by rodents, particularly the common house mouse and some rat species. People get infected through direct contact with rodent urine, droppings, saliva, or nesting materials, or by breathing in particles from these sources. In most healthy adults, the infection causes a mild illness with fever, fatigue, muscle aches, nausea, and headache. Some people develop meningitis, but fatal cases are rare in people with healthy immune systems.
The real danger is during pregnancy. LCMV infection in the first or second trimester can cause severe developmental problems in the fetus, including fluid buildup in the brain, vision loss, and developmental delays. The virus does not spread from person to person under normal circumstances.
Salmonella
Rats contaminate food and food preparation surfaces with Salmonella bacteria through their droppings. The bacteria can persist in the environment for long periods, surviving on surfaces, in bedding, and in transport containers. One documented outbreak traced multidrug-resistant Salmonella Typhimurium back to contaminated rodent cages and bins, where the bacteria lingered and spread to animals housed later in the same containers.
For people, Salmonella infection causes diarrhea, fever, and abdominal cramps, typically starting 12 to 72 hours after exposure. Most cases resolve on their own, but the drug-resistant strains rats sometimes carry can make treatment more complicated if the infection becomes severe.
Pet Rats vs. Wild Rats
Many pet rat owners assume their animals are disease-free because they were bred in captivity and kept indoors. The reality is more nuanced. A serosurveillance study of 79 pet rat owners in the UK found that 34% had antibodies for hantavirus, with the vast majority positive for Seoul virus, a strain carried by brown rats. Testing of one breeding colony found Seoul virus in 81% of the rats sampled. Pet rats can carry and transmit the same pathogens as their wild counterparts, particularly when breeding colonies are not screened.
That said, wild rats pose a broader range of risks simply because of their environment. They wade through sewers, scavenge from garbage, host more flea species, and leave droppings across surfaces where people live and eat. Pet rats are less likely to carry plague-associated fleas or Salmonella from contaminated food sources, but they are not inherently safe from a disease standpoint.
How to Safely Clean Up After Rats
The single most important rule: never sweep or vacuum rat droppings, urine, or nesting material. Doing so launches viral particles into the air, which is exactly how hantavirus spreads. Instead, follow a specific sequence designed to kill pathogens before disturbing anything.
Start by opening all doors and windows and leaving the area for 30 minutes to ventilate. When you return, spray all droppings and urine with a household disinfectant or a bleach solution (1.5 cups of bleach per gallon of water). Let the solution soak for at least 5 minutes. Then pick up the material with paper towels and dispose of it in a sealed bag. Nesting materials should also be sprayed until fully soaked before removal.
For large infestations or enclosed spaces like attics and crawlspaces, the CDC recommends wearing a half-mask respirator with a HEPA filter. Rubber gloves are essential for any cleanup. Wash your hands thoroughly with soap and water afterward, even if you wore gloves the entire time.