Do Rats Really Spread Diseases? What the Research Says
Rats have long inspired fear in people. Historically, they were blamed for spreading the plague, and today media outlets often speak about “rat infestations” and the diseases they supposedly transmit.
The reality, however, is more complex. In cities with good sanitation systems, the health risk posed by free-living rats is relatively low. This does not mean the issue does not exist—but it also does not justify the use of brutal control methods that remain common, including in Poland.
Rats and Diseases – What Research Shows
The brown rat and the black rat can carry various microorganisms that cause disease. In a review of studies published between 1995 and 2016, scientists identified 53 pathogens potentially associated with rats. Of these, 48 were linked to brown rats and 20 to black rats.
These numbers are often cited as evidence that rats are particularly dangerous. However, it is important to remember a key distinction: the ability to carry a pathogen is not the same as actual human infections, hospitalizations, or deaths.
The real risk depends largely on the conditions in which people live—such as the quality of sanitation infrastructure, climate, and access to healthcare. The mere presence of rats and the number of pathogens they can theoretically carry do not automatically translate into a public health threat.
The Disease Most Often Associated with Rats
Leptospirosis is the disease most commonly associated with rats. Globally, about 1 million cases are reported each year, mostly in regions with warm climates, weaker sanitation infrastructure, and after flooding events. Infection typically occurs through contact with water contaminated by rat urine.
In Europe, the situation is very different. According to the European Centre for Disease Prevention and Control (ECDC), 12,180 cases were confirmed in the EU between 2010 and 2021, which averages about 1,015 cases per year.
In Poland, 43 cases were recorded during the same period, or about 3–4 cases annually.
Some infections may go undiagnosed, but severe illness is relatively rare. Among 5,161 EU cases with known outcomes, 135 deaths were recorded (2.6%). In Poland, there are no reported deaths caused by leptospirosis. A 2024 report by the National Institute of Public Health, covering 17 cases recorded between 2023 and 2024, does not list leptospirosis among causes of death from infectious diseases.
A “Rodent” Is Not Always a Rat
Hantaviruses are also often mentioned in discussions about rat-borne diseases. A common mistake, however, is to assume that all hantaviruses are associated with rats—based on the simplified idea that “rodent = rat.”
In Europe, most infections are caused by the Puumala virus (PUUV), which is transmitted almost exclusively by the bank vole (Myodes glareolus). According to a review by Joanna Stojak, this virus is responsible for more than 98% of hantavirus infections in Europe.
Free-living rats mainly carry the Seoul virus (SEOV). Although this virus accounts for roughly 25% of hantavirus infections globally, its role in European cases is marginal.
For this reason, rats may pose a significant health risk in some parts of the world, such as East Asia, but in Europe and Poland they do not significantly contribute to the number of infections.
Diseases Often Attributed to Rats
Other diseases frequently linked to rats—such as salmonellosis, Lyme disease, tularemia, murine typhus, or plague—are in reality only weakly connected to them or occur very rarely in cities with high sanitation standards.
For example, salmonellosis is most commonly contracted through contaminated food, especially eggs and meat.
Lyme disease is transmitted by ticks. While rats may play a role in the spread of ticks, the main reservoirs of the bacteria are voles and wood mice.
Diseases such as murine typhus, tularemia, or hymenolepiasis are now so rare in Europe that they are not even listed in epidemiological reports by the European Centre for Disease Prevention and Control or Poland’s National Institute of Public Health.
The plague, often invoked in discussions about rats, currently causes around 1,000–3,000 cases globally each year.
For comparison, diseases linked directly to human activities — such as air pollution, tobacco use, or unhealthy diets — cause hundreds of thousands or even millions of deaths annually in cities worldwide.
Rats and Other Urban Animals
Rats are not the only animals in cities capable of transmitting diseases. While animals such as hedgehogs, foxes, or squirrels are less often discussed in this context, dogs and cats—animals widely loved by people—can transmit a similar number of zoonotic diseases as rats.
It is estimated that dogs may carry 60–70 pathogens, while cats may carry around 40.
Rabies, which is transmitted by dogs in 99% of cases, causes about 60,000 deaths worldwide each year. Meanwhile toxoplasmosis, associated among other factors with cats, may infect 30–50% of the global human population.
At the same time, rabies cases in Europe are now extremely rare, and research shows that simply owning a cat does not significantly increase the risk of toxoplasmosis. For this reason, drastic preventive measures are not applied to dogs or cats.
Why Are Rats Treated Differently?
This may be the result of prejudice against this species. Even though data do not indicate a major epidemiological threat in European cities, rats are often met with disproportionate hostility.
This does not mean that other animals should be controlled with the same severity. On the contrary—it highlights the need to seek effective and more humane ways of coexistence, also with rats, which are sentient animals and part of urban ecosystems.
Intensive Rat Control Does Not Solve the Problem
The risks associated with rats in cities should not be completely ignored. These animals can carry microorganisms that may pose a threat under certain conditions. Scientists also note that rising temperatures and more frequent natural disasters may increase the occurrence of some diseases.
In practice, however, even in places where rats are abundant, the number of infections, hospitalizations, and deaths remains very low.
Meanwhile, many pest-control measures rely on methods that often ignore animal welfare. Research by Mason and Littin shows that glue traps and anticoagulant poisons are among the most commonly used—and least humane—methods. They cause prolonged suffering and fail to solve the problem in the long term.
Poisons are also dangerous for the environment and can lead to secondary poisoning of other animals, such as birds of prey.
Time for a Change
What this means is that a shift in perspective is needed. The real issue is not the rats themselves, but the microorganisms that may be associated with them.
The most effective prevention measures remain systemic actions:
- proper waste management
- urban hygiene
- public education
- access to healthcare
Combined with thoughtful urban planning and humane population management, these measures can allow for safer and more responsible coexistence between people and rats in cities.
Substantive review: Maksym Tarnowski, University of Wrocław
References
Beauté J., Innocenti F., Aristodimou A., Špačková M., Eves C., Kerbo N., Rimhanen-Finne R., Picardeau M., Faber M, Dougas G., Halldórsdóttir A. M., Jackson S., Leitēna V., Vergison A., Borg M. L., Pijnacker R., Sadkowska-Todys M., Martins J. V., Rusu L. C., Grilc E., Estévez-Reboredo R. M., Niskanen T., Westrell T. (2024) Epidemiology of reported cases of leptospirosis in the EU/EEA, 2010 to 2021. Euro Surveill, 29(7):2300266. https://doi.org/10.2807/1560-7917.ES.2024.29.7.2300266
Centers for Disease Control and Prevention (CDC). (2024). Leptospirosis – About leptospirosis. https://www.cdc.gov/leptospirosis/about/index.html
Chanamé Pinedo, L., Mughini-Gras, L., Franz, E., Hald, T., & Pires, S. M. (2022). Sources and trends of human salmonellosis in Europe, 2015-2019: An analysis of outbreak data. International journal of food microbiology, 379, 109850. https://doi.org/10.1016/j.ijfoodmicro.2022.109850
Chomel, B. (2014). Emerging and re-emerging zoonoses of dogs and cats. Animals, 4(3), 434–445. https://doi.org/10.3390/ani4030434
European Centre for Disease Prevention and Control (ECDC). (2023). Leptospirosis – Factsheet. https://www.ecdc.europa.eu/en/leptospirosis/factsheet
Gawor, J., Stypułkowska-Misiurewicz, H., & Rabczenko, D. (2018). Leptopspiroza w Polsce w latach 2014-2017. Charakterystyka zakażeń i dane z nadzoru. Przegląd Epidemiologiczny, 73(2), 179–188. https://doi.org/10.32394/pe.72.3.7
Himsworth, C. G., Parsons, K. L., Jardine, C., & Patrick, D. M. (2013). Rats, cities, people, and pathogens: a systematic review and narrative synthesis of literature regarding the ecology of rat-associated zoonoses in urban centers. Vector borne and zoonotic diseases, 13(6), 349–359. https://doi.org/10.1089/vbz.2012.1195
Mason, G. J., Littin, K. E. (2003). The humaneness of rodent pest control. Animal Welfare, 12, 1–37. https://doi.org/10.1017/S0962728600025355
Meerburg BG, Singleton GR, Kijlstra A. (2009). Rodent-borne diseases and their risks for public health. Crit Rev Microbiol. ;35(3):221-70. https://doi.org/10.1080/10408410902989837
Naik, H. S., Radha, S., Charitha, V. G., & Raghu, B. (2025). Household pets and zoonotic pathogens: A public health perspective. International Journal of Veterinary Sciences and Animal Husbandry, 10(4), 141–147. https://www.veterinarypaper.com/archives/2025/10/4/C/10-4-16
Narodowy Instytut Zdrowia Publicznego PZH – PIB. (2024). Choroby zakaźne i zatrucia w Polsce w 2024 roku. https://www.pzh.gov.pl
Richter D, Schlee D. B., Matuschka F. R. (2011). Reservoir competence of various rodents for the lyme disease Spirochete Borrelia spielmanii. Appl Environ Microbiol. Jun;77(11):3565-70. https://doi.org/10.1128/AEM.00022-11
Rynek Zdrowia. (2024). Szczury zagrożeniem epidemiologicznym. Leptospiroza to nie jest najgorsza możliwość. https://www.rynekzdrowia.pl/Polityka-zdrowotna/Szczury-zagrozeniem-epidemiologicznym-Leptospiroza-to-nie-jest-najgorsza-mozliwosc
Stojak J. (2020). Hantavirus infections in humans in Poland-current state of knowledge and perspectives for research. Eur J Public Health. Oct 1;30(5):982-985. https://doi.org/10.1093/eurpub/ckz144
Strand, T. M., & Lundkvist, Å. (2019). Rat-borne diseases at the horizon. A systematic review on infectious agents carried by rats in Europe 1995–2016. Infection Ecology & Epidemiology, 9(1). https://doi.org/10.1080/20008686.2018.1553461
Wojewódzka Stacja Sanitarno-Epidemiologiczna w Poznaniu. (2025). Dżuma. https://www.gov.pl/web/wsse-poznan/dzuma