Leptospirosis

Leptospirosis is a zoonosis (i.e., a human disease with an origin in animals) caused by Leptospira bacteria. Leptospirosis is a widespread disease with more than 1 million diagnosed cases annually around the globe (Thibeaux et al., 2018). In Europe, leptospirosis remains a relatively uncommon disease (ECDC, 2014-2023). Worldwide, only one out of ten infections is believed to be correctly diagnosed globally (Samrot et al., 2021) due to the variety of symptoms (if any) and their similarity with symptoms of other diseases. Urban areas are increasingly at risk, especially during floods caused by heavy rains. Both global warming and changes in rainfall patterns have the potential to increase the disease burden in Europe, with more frequent extreme weather events and floods probably posing the highest risk for more leptospirosis infections in the future.

Leptospirosis notification rate (map) and reported cases (graph) in Europe

_{Source: ECDC, 2024, Surveillance Atlas of Infectious Diseases}

_{Notes: Map and graph show data for the EEA member countries. The boundaries and names shown on this map do not imply official endorsement or acceptance by the European Union. The boundaries and names shown on this map do not imply official endorsement or acceptance by the European Union. The disease is notifiable at the EU level, but the reporting period varies among the countries. When countries report zero cases, the notification rate on the map is shown as '0'. When countries have not reported on the disease in a particular year, the rate is not visible on the map and is labelled as 'unreported' (last updated in September 2024).}

Source & transmission

Many different strains of Leptospira bacteria can cause infections and a variety of clinical signs in humans and several animals (including wild and domestic animals, mammals, reptiles and amphibians). Humans usually contract leptospirosis via ingestion of or skin contact with contaminated soil, water, vegetation, or via contact with infected animals or their urine. Outbreaks are often associated with contaminated rivers, streams, canals or lakes. In industrialized countries, exposure to Leptospira-contaminated water during recreation or occupational activities increases leptospirosis infection risk, while in developing countries, infections are often linked to exposure to untreated wastewater and animal faeces. Another, yet less important, disease transmission pathway is the inhalation of contaminated aerosols. Direct person-to-person transmission is rare (Mwachui et al., 2015).

Health effects

Most often, Leptospira infections do not cause any or only mild symptoms, which complicates proper diagnosis. If symptoms manifest themselves - usually around 10 days after infection - these include sudden fever, headaches, chills, muscle aches, or eye inflammation. The latter is a very specific symptom of leptospirosis that would affect between 10 and 44% of all patients in Europe (Rathinam, 2005). More severe symptoms of the disease include inflammation of the brain and spinal cord (meningitis), rashes, destruction of red blood cells (anaemia), uncontrolled bleeding and slime formation, severe kidney failure, yellow skin coloration, mental confusion and depression, inflammation of the heart muscle (myocarditis), or even multi-organ failure. The illness usually lasts from a few days to 3 weeks or even longer. Recovery of untreated cases can take several months. Delayed symptoms can include chronic fatigue, paralysis, depression and eye infections (CDC, 2022; De Brito et al., 2018; Haake and Levett, 2015; Samrot et al., 2021).

Morbidity & mortality

In the EEA member countries (excluding Liechtenstein, Norway, Switzerland and Türkiye due to absence of data), in the period 2007-2023:

• 11,752 confirmed infections
• 0.30 cases per 100 000 population in 2023 (up from 0.18 in 2022).
• High hospitalisation rate: > 90%[1]
• 176 deaths and an average mortality rate of 3%. Yet, in case of severe symptoms, mortality rate rises to 5-20%, especially for untreated patients with kidney failure (Calvopiña et al., 2018).
• Increasing incidence trend since 2015 with 2023 cases being the highest reported since 2007. In 2020, leptospirosis incidence dropped to the 2015 level, but this may have been driven by population behaviours and disrupted surveillance activities related to Covid-19. In 2021, cases increased again.

 (ECDC, 2024-2023; 2023)

Distribution across population

• Age group with the highest disease rate in Europe: 25-64 years old males, 15-24 years old females (ECDC, 2014-2023)
• Groups at risk of severe disease course: elderly and people with a weak immune system
• Groups at higher risk of infection: people who are in contact with contaminated water, soil or infected animals at work, e.g., veterinarians, farmers, fishermen, mine workers or military troops, as well as sportsmen, swimmers, bathers or travellers (Bandara et al., 2014; Mwachui et al., 2015). The disease is more common among males (ECDC, 2014-2023).

Climate sensitivity

Climatic Suitability

Leptospira spp. thrive best at temperatures between 28 and 30°C, and pH ranges between 6.8 and 7.4 in a lightly salt water environment (Bharti et al., 2003; Wongbutdee et al., 2016).

Seasonality

In Europe, infections mostly occur between July and October with a peak in August-September. This seasonal pattern is probably driven by a combination of climatic factors (e.g., presence of heavy rainfall events and high temperatures) and human behaviour (e.g., increase in outdoor activities) (ECDC, 2014-2023).

Climate Change Impact

Higher annual mean temperatures enhance the growth and activity of Leptospira spp., and at the same time lengthen the infectious season and expand the geographical distribution of the bacteria. Also higher rainfall amounts and more moist conditions are linked to increased Leptospira spp. growth and survival. Projected changes are expected to increase the disease burden (Desvars et al., 2011; Pawar et al., 2018). Another important future climatic risk factor for leptospirosis infections is the increased frequency of extreme weather events. Heavy rainfall, storms and associated flooding events increase human exposure to contaminated water (Bharti et al., 2003), particularly in combination with poor sanitation, insufficient healthcare or crowded conditions, this could expose people to increased infection risks (Mwachui et al., 2015). Drought episodes on the other hand stimulate recreational activities like swimming and bathing, and the risks of occupational exposure for example when farms use alternative, contaminated water sources in periods of drought and water use restrictions. Both might lead to an increase in leptospirosis infections.

Prevention & Treatment

Prevention

• Avoiding or limiting contact with potentially contaminated water or infected animals
• Protective clothing, especially when exposed to potentially contaminated water or infected animals in working environments
• Public water safety to avoid infections during recreational activities
• Vaccination of livestock and pets and rodent control to reduce animal-to-person infections
• Awareness raising about infection pathways
• (CDC, 2022; Jittimanee and Wongbutdee, 2019)

Treatment

• Antibiotics

References

Bandara, M., et al., 2014, Globalization of leptospirosis through travel and migration, Globalization and Health 10(61), 1-9. https://doi.org/10.1186/s12992-014-0061-0

Bharti, A. R., et al., 2003, Leptospirosis: A zoonotic disease of global importance, The Lancet Infectious Diseases 3(12), 757–771. https://doi.org/10.1016/S1473-3099(03)00830-2

Calvopiña, M., et al., 2022, Leptospirosis: Morbidity, mortality, and spatial distribution of hospitalized cases in Ecuador. A nationwide study 2000-2020, PLOS Neglected Tropical Diseases 16(5), e0010430. https://doi.org/10.1371/journal.pntd.0010430

CDC, 2022, Centers for Disease Control and Prevention, https://www.cdc.gov. Last accessed August 2022.

De Brito, T., et al., 2018, Pathology and pathogenesis of human leptospirosis: A commented review. Revista Do Instituto de Medicina Tropical de São Paulo 60(e23), 1-10. https://doi.org/10.1590/s1678-9946201860023

Desvars, A., et al., 2011, Seasonality of Human Leptospirosis in Reunion Island (Indian Ocean) and Its Association with Meteorological Data, PLoS ONE 6(5), e20377. https://doi.org/10.1371/journal.pone.0020377

ECDC, 2014-2023, Annual epidemiological reports for 2012-2021 – Leptospirosis. Available at https://www.ecdc.europa.eu/en/leptospirosis/surveillance-and-disease-data. Last accessed August 2023.

ECDC, 2024, Surveillance Atlas of Infectious Diseases. Available at https://atlas.ecdc.europa.eu/public/index.aspx. Last accessed September 2024.

Haake, D. A. and Levett, P. N., 2015, Leptospirosis in Humans. In: Adler, B. (Ed.), Leptospira and Leptospirosis, Current Topics in Microbiology and Immunology vol. 387, Springer Berlin Heidelberg, pp 65–97. https://doi.org/10.1007/978-3-662-45059-8_5

Jittimanee, J. and Wongbutdee, J., 2019, Prevention and control of leptospirosis in people and surveillance of the pathogenic Leptospira in rats and in surface water found at villages, Journal of Infection and Public Health 12(5), 705–711. https://doi.org/10.1016/j.jiph.2019.03.019

Mwachui, M. A., et al., 2015, Environmental and Behavioural Determinants of Leptospirosis Transmission: A Systematic Review, PLOS Neglected Tropical Diseases 9(9), e0003843. https://doi.org/10.1371/journal.pntd.0003843

Pawar, S. D., et al., 2018, Seasonality of leptospirosis and its association with rainfall and humidity in Ratnagiri, Maharashtra, International Journal of Health & Allied Sciences 7, 37–40. https://doi.org/10.4103/ijhas.IJHAS_35_16

Rathinam, S. R., 2005, Ocular manifestations of leptospirosis, Journal of Postgraduate Medicine 51(3), 189-194. https://pubmed.ncbi.nlm.nih.gov/16333191/

Samrot, A. V., et al., 2021, Leptospiral Infection, Pathogenesis and Its Diagnosis—A Review,  Pathogens 10(2), 145. https://doi.org/10.3390/pathogens10020145

Thibeaux, R., et al., 2018, Biodiversity of Environmental Leptospira: Improving Identification and Revisiting the Diagnosis, Frontiers in Microbiology 9, 1-14. https://doi.org/10.3389/fmicb.2018.00816

Wongbutdee, J., et al., 2016, Perceptions and risky behaviors associated with Leptospirosis in an endemic area in a village of Ubon Ratchathani Province, Thailand, African Health Sciences 16(1), 170-176. https://doi.org/10.4314/ahs.v16i1.23

[1] Hospitalisation rate is based on data analysis of cases with known hospitalization status. Completeness of data on hospitalization is provided since 2009 and varies between 0 and 100% for different countries. Overall, for around 50% of all reported cases in Europe, also the hospitalization status is reported.