Rat in the House? 4 Diseases Spread by Rats That You Should Know About

When you spot a large, long-tailed creature sprinting across the kitchen floor, you may want to take pest control into your own hands without a second thought. Yet even close proximity to a rat—or what they leave behind—could expose you to a handful of bacterial and viral diseases common in North America. 

We'll walk through the most common rat-borne diseases, how they spread, and how to protect yourself from something far more malicious than a small pest problem.

1. Hantavirus Pulmonary Syndrome

According to the Centers for Disease Control and Prevention (CDC), several varieties of the hantavirus turn up across the United States from a range of rodents. Both mice and rats can carry the virus, so you'll find the virus anywhere from the marshes in the south to the heart of NYC. The virus is still very rare, but it can result in a dangerous and even fatal respiratory illness, even in healthy patients. 

Types of Rats

Hantavirus pulmonary syndrome commonly spreads through cotton rats and rice rats. Both of these species prefer southern states’ heat and humidity. But since common mice carry the virus throughout the rest of the country, it's good to call a pro to handle any unidentified rodent in your home just in case.

How It Spreads

As is commonly the case, the biggest threat here is a rodent's urine or feces. Infected rodents will spread the viral particles around your home, both in their leftovers and their saliva. Breathing in contaminated air or coming in contact with the droppings and bodily fluids can expose you to the virus. While bites can also spread the disease, it’s incredibly rare.

2. Leptospirosis

Rats commonly carry dangerous bacteria as well, and leptospirosis is one of the more commonly spotted in North America. While still very rare—about 100–150 cases of the infection turn up in the country each year—it's essential to take extra care against the threat.

The bacterial infection can cause flu-like symptoms very easily confused with other illnesses. In some cases, leptospirosis can progress into more severe complications like meningitis or kidney and liver failure.

Types of Rats

Wild rats across the country can carry the leptospirosis bacterium, but it also appears in many larger rodents and farm animals.

How It Spreads

Exposed mucous membranes—we're taking when you're eating, drinking, or have cuts on your hands—are the main threat here. In addition to spreading the bacteria through direct contact, infected rodents can contaminate water, food, and soil. Floodwaters after a large storm pose a particular threat for this reason.

3. Rat-Bite Fever

Spotting a rat in your home may be the most obvious sign you have an infestation. If the sight of a rat sends you leaping onto a chair in fear of getting bit, that's totally understandable. But the name of rat-bite fever is a bit deceiving. You'll see below that the disease can transmit in several ways beyond an attack.

The disease itself can lead to fever, vomiting, headaches, muscle pain, and more rare symptoms like rash and joint swelling. Streptobacillary RBF—the common strain found in North America—can lead to more extreme liver, brain, lungs, and heart infections.

Types of Rats

The western streptobacillus moniliformis strain of RBF transfers through many wild rats throughout the country. In some cases, mice may carry the bacteria as well.

How It Spreads

Overall, rat bites are still relatively rare, but never something you want to mess with. The CDC recommends contacting your healthcare professional if you know you've been scratched or bitten by a rat or if you develop symptoms after spending time near a rodent. Rat-bite fever transmits to humans in a handful of ways, however. These include:

• Exposure to rat feces, urine, and other bodily fluids

• Eating or drinking contaminated fluids and food

• Contact between contaminated surfaces and mucous membranes

• Bite wounds and scratches

4. Salmonellosis

Salmonella may bring up the image of raw chicken or a romaine lettuce recall, but the threat of the bacteria lurks in many other sources as well—including rats and mice. Salmonellosis affects the digestive tract, leading to stomach cramps, fever, and diarrhea. The most at-risk populations include those with weakened immune systems, including children and older adults.

Types of Rats

Salmonella has many common carriers, including all common wild rats and mice across the country. The list also includes common pocket pets like guinea pigs and hamsters—including the class pet you're watching for the weekend. Always be sure to practice thorough hygiene when handling these animals.

How It Spreads

Like many of the illnesses on our list, this bacteria primarily travels through food and water. But handling items with bodily fluids infected with the bacteria is also an issue. The CDC recommends washing your hands whenever you come in contact with a rodent—even a pet rat in their cage.

Preventing Rat-Borne Diseases

Even the cleanest homes get their fair share of scurrying creatures from time to time. Small cracks in your roof, foundation, windows, and doors provide common entry points for rats. The moment you detect a rat or other rodent in your home, or even an overabundance in your garden, be sure to call your local pest control company.

Not only can catching the problem early help prevent disease, but it will also keep exterminator costs low before the infestation takes off. In the meantime, consider instituting preventative measures to catch rodents the second they enter your home—but always consult a professional before attempting to handle rats or their waste directly.