8 Reasons Why Rats Carry So Many Diseases

Brown pet rat in a cage

Rats pose many dangers to human health and have long been avoided and feared due to the deadly diseases they carry and can spread to the people they come into contact with. 

Rats are perfect vectors for disease because of their living habits, the foods they eat, and their social natures. All these traits leave them with a greater chance of picking up a disease, while their strong immune systems help them survive and eventually pass these illnesses on to humans or other animals. 

In this article, we examine exactly why rats are so great at carrying diseases, the most common ones they can transmit to humans, and if there’s anything you can do to reduce the chance of you ending up with one of their many, many viruses, bacterias, or parasites.

The Top 8 Reasons Why Rats Make Great Disease Carriers

1. They Love Dumpster Diving

Alright, who are we to judge when rats turn to trash cans, rubbish dumps, and litter-strewn streets to scavenge for food and find safe nesting places?

Rats are incredibly good at surviving in even the most squalid conditions, and their perseverance is inspiring. Unfortunately, their decision to make garbage bins their homes also means they’re exposed to many diseases from a wide variety of sources. 

Many rodents, including rats, depend on food waste as their primary source of sustenance. Therefore, they call some of the dirtiest places on earth their homes. 

They will stay in sewerage networks, drains, and abandoned buildings despite the number of health code violations these locations produce. 

As a result of these filthy conditions, rats are exposed to almost every disease known to humankind, including bacteria growing on old food, worms in expired meat, viruses spread from old tissues or fecal matter, and parasites that also choose to thrive on waste. 

Some other disease-infested locations rats frequent include: 

  • Cesspools: Although it’s unthinkable for any living creature to survive in or near a cesspool, rats do so relatively well. They not only mind the smell but believe it or not, rats can swim up through cesspool pipes and into your toilet. Most rats can swim comfortably for up to three days and can hold their breath for quite some time too. [Source]
  • Sewers: If you’ve ever watched a movie starring any type of rat — Ratatouille being the pinnacle, of course — you know they often use sewers as living places or personal highways. Far below the city, rats use sewers to move from one place to another without the danger of being caught or killed by humans or cars. 

Unfortunately, sewers and cesspools are the main transport system for the most deadly forms of human waste that could be home to millions of bacteria and disease-causing organisms. All it takes is for a rat to take a sip of sewer water or inhale airborne droplets, and it instantly becomes a carrier of whatever illness fate chose to provide it with. 

2. They Have Incredibly Strong Immune Systems

Being exposed to so many diseases has one benefit: developing an all-powerful immune system that can resist almost every disease known to man. 

This is great for rats but not so great for humans. Since rats don’t simply die from whatever diseases they collect as they go through life, they make excellent vectors for passing those illnesses on to other rats, animals, and people. 

Instead of disease X killing them two days after they contracted it, they simply continue on their merry way, infecting every other living being they encounter and collecting even more sicknesses as they go. 

3. They’re Social Creatures

Rats are incredibly social animals who enjoy living and nesting in groups. As a result, rats share their diseases and can quickly double or triple the viruses, parasites, and bacteria they carry.

And if sharing a nest wasn’t enough to spread their sicknesses, rats have complex communications systems that function through touch and smell, all of which bring them into close contact with each other, increasing their chances of infecting their fellows with their own illnesses while contracting the diseases spread by others in the group.

4. They Season Their Food

Far be it from rats to separate their food stores from their toilet facilities. Rats urinate and poop on or around their own food on a regular basis. 

Some believe they do so to discourage other rats from stealing their grub, hoping to share some of their many diseases with the thieves should they not heed the smelly warning. 

But rats don’t seem to be all that fazed by eating urine-soaked, poop-covered food, as long as it will fill their bellies. Most rats won’t even hesitate to eat their own fecal matter, much less that of another animal. 

That’s because rats have a unique digestive system that doesn’t absorb all the nutrients from their food the first time around (a process called coprophagy).

That means poop makes an excellent source of nutrients for any hungry rat. Despite this unique survival mechanism, eating biological waste comes at a price. You consume the full spectrum of bacteria, viruses, and internal parasites the owner of the poop may have had. 

And so, through their weird dietary habits, rats also collect diseases to add to their already growing spectrum and possibly pass them on to other animals and people.

White and grey pet rat in a cage

5. Their Diets are Questionable

What people and animals consume can be one of the most significant sources of disease if not handled hygienically or cooked correctly. Unfortunately, most rats do not resemble the adorable Remi from Ratatouille. They would much rather feast on anything they come across than go off in search of the perfect, wild mushroom to accompany their foie gras. 

Organic matter is the breeding ground for all sorts of organisms like bacteria, viruses, and worms.

Rats are omnivores which means they’ll eat pretty much anything their bodies can digest, including garbage, old meat, and even leather or wood. 

Such an array of expired food can provide a significant source of disease to rats who consume it and add a nice contribution to the already growing number of diseases these rats carry.  

6. They Play Host to a Variety of Parasites

Rats carry fleas and ticks, which can give them sickness from other animals. 

Parasites often feed on the blood of animals and humans to survive. Although ticks don’t typically live in suburban or city areas, rats do come into contact with them as they travel through life and may eventually become host to a few bloodsuckers. 

Due to the close contact between rats in the same group or nest, fleas and ticks can transfer from one rat to another, effectively transporting the full range of sicknesses carried by one rat to another. 

7. They Get Into Fights

If neither proximity nor sharing of parasites has transferred disease from one rat to another, a fight ought to do it. 

Since rats live in groups, it’s natural for fighting to break out as one or more rats try to assert dominance over the others. Unfortunately, fighting can lead to biting, and the rat being bitten may be infected with all the bacteria present in another rat’s mouth. 

8. They Love Traveling

Rats move around a lot and can transport diseases between suburbs, cities, or even countries! Once they reach new territory, they can very quickly infect all the rats in the area, even if the diseases they carry never existed there before. 

It’s one of the reasons why, no matter where you are in the world, most rats carry a similar spectrum of diseases.

Transmission to Humans

Due to the large variety of diseases rats carry, there’s a good chance at least some are transferable to humans. 

Rats can infect humans with their sicknesses through bites, physical contact, or by urinating and defecating near the food we eat, with often devastating consequences.

Most Common Diseases Carried By Rats

Rats can carry around 35 known diseases at any one time, many of which are transferable to humans. 

The most common diseases carried by rats include: 

1. Hantavirus

Hantavirus is a deadly disease that will infect the lungs. Infected rats transmit the virus to humans, and there is currently no treatment or vaccine for it.

Symptoms of hantavirus include:

  • Fever
  • Headaches
  • Fatigue
  • Muscle pain
  • Diarrhea
  • Nausea and vomiting

2. Lymphocytic Choriomeningitis

Lymphocytic meningitis is transmitted through contact with rat saliva or urine.

Lymphocytic choriomeningitis usually appears in two stages and presents with the following symptoms: 

  • Nausea
  • Vomiting
  • Headaches
  • Muscle pain
  • Reduced appetite

3. The Plague

The bubonic plague is long gone after killing millions across Europe, but did you know that it was most likely carried and spread by rats? 

More specifically, by the fleas that often hitch rides on rats. 

Eventually, people with the plague developed pneumonia and transmitted the disease to others through coughing and sneezing. 

Despite the bubonic plague happening ages ago, there is always the possibility of a new, even deadlier version. The new plague could be transferred to humans through rats. 

4. Salmonella

Salmonella isn’t only caused by eating poorly cooked chicken. Many rodents, including rats,  carry salmonella bacteria in their digestive tracts. 

If humans come into contact with their droppings or even just trace amounts of their poop, the bacteria can be spread. 

The main symptoms of salmonella infection are:

  • Chills
  • Fever
  • Nausea and vomiting
  • Diarrhea

5. Rat-Bite Fever

Rat-bite fever is a severe disease that is transmitted if you get bitten by an infected rat. Even if you don’t show any symptoms, you must go to the doctor for treatment if a rat bit you. 

The symptoms that typically present in a person with rat-bite fever include:

  • Fever
  • Rash
  • Headaches
  • Vomiting
  • Muscle pain

6. Lassa Fever

Lassa fever is another neat viral infection transmitted by rats. It is transferred through contact with the saliva, urine, or droppings of an infected rat and can also be shared from one person to another.

The symptoms of Lassa fever are:

  • High temperature (fever)
  • Sore throat
  • Muscle pains
  • Headache

These are only the top six of a total of 35 diseases commonly carried by rats. 

Wild or city rats are typically the most infected by disease. There’s a good reason why most people warn you to keep away from them and avoid eating any food that you suspect may be contaminated with their droppings or bodily fluids.

How To Avoid Getting Diseases Spread by Rats

  • Keep your house and kitchen clean: Rats prefer to live in messy, dirty environments. Keeping your surroundings clean will reduce the chance of any rodent visitors coming by to share their illnesses. Swiftly pick up any loose food or crumbs, and a solid all-purpose cleaner is a helpful tool to quickly wipe down surfaces.
  • Don’t try to catch rats on your own: If you see a rat in your house or near you, do not try to catch it. Rats clean themselves by licking their fur, so even just touching an infected rat could lead to that disease being transferred to you.
  • Don’t touch things rats have been near: Rats poop and urinate as they move, so even a countertop that a rat has just run across may contain traces of bacteria. Always wear gloves when cleaning surfaces rats have come into contact with. 
  • Never try to make a wild rat your pet: Not only will most wild rats refuse to be tamed, but wild or city rats carry the most diseases and may bite you in the process of catching or taming them, thus making you sick as well. 
  • If you get bitten, go to the doctor immediately: Even if you’re not showing any symptoms, you must get treatment from a nurse or doctor for any possibly transmitted infections.

Do Pet Rats Carry Diseases?

All animals carry a form of disease at some point in their lives. However, most pet rats bought from pet shops are raised in captivity from birth and likely were never exposed to any of the diseases mentioned above. 

Taking proper care of your pet rat is also essential to prevent it from contracting bacteria or viruses. This includes always cleaning out old food and replacing its water regularly to keep it fresh. 

If you own more than one rat, keeping their cage clean is even more important. Removing feces and urine-soaked bedding daily is essential. 


Although rats can be adorable critters, they carry a myriad of deadly diseases. This means you’ll be wise to steer clear of any wild or city rats. But thankfully, there’s no reason to stop cuddling and loving your pet shop-bought friend.

Other good reads