Leptospirosis is caused by a strain of bacteria called leptospira, which are found in certain animals including:
- mice
- rats
- pigs
- cattle
- horses
- dogs
- sheep
- bats
- raccoons
The bacteria live inside the animal’s kidneys and can be passed out in their urine. Bacteria passed into soil or water can survive for several weeks or even months.
You can become infected by the leptospira bacteria by drinking contaminated water, or if contaminated water or soil comes into contact with your eyes, mouth, nose or any unhealed cuts in the skin. Less commonly, the infection can be passed on to humans who come into close physical contact with the blood of an infected animal.
Human cases of leptospirosis are rare, but occasional outbreaks can occur, particularly at events that involve close contact with infected water sources, such as competitive freshwater swimming. It is also possible for a person to become infected after a natural disaster, such as a flood.
Human to human transmission of infection is rare, but thought to occur during sex or by an infected mother passing on the infection to her baby while breastfeeding.
Geographical risk factors
Leptospirosis is found throughout the world, including Western Europe, but it is most common in tropical and subtropical areas. This is because the leptospira bacteria are able to survive longest in hot and humid conditions. The countries and regions where leptospirosis is most common include:
- India
- China
- Southern Russia
- South East Asia
- Africa
- parts of Australia
- Central America
- parts of South America (particularly Brazil)
- the Caribbean
Popular tourist destinations that have a higher-than-average rate of leptospirosis include:
- Hawaii
- Jamaica
- Barbados
- Australia
- New Zealand
If you are travelling to these parts of the world, there are certain outdoor activities that could bring you into contact with contaminated water or soil and may place you at a slightly higher risk of contracting leptospirosis. For example:
- camping in rural areas
- sailing
- swimming, particularly if you submerge your head under the water for long periods of time
- rafting
- caving or potholing
- canoeing
- trail biking
- walking barefoot
Areas of the developing world where there has been sudden flooding tend to have an associated outbreak of leptospirosis. This is because previously clean sources of drinking water can become contaminated by flood water.
Occupational risk factors
There are several occupations that increase your risk of contracting leptospirosis. However, this risk is only significant if you are working in the parts of the world listed above rather than in England. These occupations include:
- farmers, particularly pig, cattle and rice farmers
- sewage workers
- people who regularly work with animals, such as vets
- freshwater fishermen
- people who work with dead animals, such as butchers or abattoir workers (an abattoir is where animals are killed for their meat)
See Leptospirosis - prevention for information and advice about how to reduce your risk of contracting leptospirosis.
