Leptospirosis

What is leptospirosis?

Leptospira are thin, spiral-shaped bacteria. Infected animals, especially rats, can carry them in their kidneys for months or years without getting sick and pass them in urine. The bacteria survive for weeks in warm, wet soil and fresh water.

Leptospirosis is one of the most widespread infections passed from animals to people (a zoonosis), with an estimated 1 million cases and around 60,000 deaths worldwide each year. It is most common in tropical and subtropical regions and surges after heavy rain, hurricanes and flooding. In the US, cases occur mostly in Hawaii and Puerto Rico, and sporadically elsewhere, including in cities with large rat populations.

How do you get leptospirosis?

The bacteria enter through:

• Cuts, scratches or skin softened by long immersion in water
• The eyes, nose or mouth, for example when swallowing water while swimming
• Drinking contaminated water
• Rarely, animal bites

Higher-risk activities and jobs include:

• Wading or cleaning up after floods
• Swimming, kayaking, rafting or triathlons in rivers and lakes
• Farming, especially rice paddies, dairy and pig farms
• Veterinary, slaughterhouse and sewer work
• Rodent infestations at home
• Contact with the urine of infected dogs

It almost never spreads from person to person.

Symptoms of leptospirosis

Many infections cause no or only mild symptoms. When illness occurs it often comes in two phases.

Early (acute) phase, first week

• Sudden high fever and chills
• Severe headache, often behind the eyes
• Muscle pain, typically in the calves and lower back, often very tender to touch
• Red eyes without discharge (conjunctival suffusion), a helpful clue
• Nausea, vomiting, diarrhea or abdominal pain
• Cough and sometimes a rash

Second (immune) phase

After a few days of improvement, some people get sick again as the immune system reacts to the bacteria. This can cause aseptic meningitis (headache, stiff neck), eye inflammation (uveitis) weeks to months later, or progression to severe disease.

Severe leptospirosis (Weil's disease)

About 5 to 10% of people with symptoms develop severe illness:

• Jaundice: yellow skin and eyes from liver involvement, often with deep yellow-orange coloring
• Acute kidney injury: little urine, swelling, high potassium. See acute kidney injury
• Bleeding: nosebleeds, bleeding gums, bruising, blood in urine or stool
• Pulmonary hemorrhage syndrome: coughing blood and severe breathlessness. This is the most deadly form

Other complications include heart inflammation with irregular rhythms, low platelets and sepsis-like shock. Death rates in severe disease range from about 5 to 15%, and are higher with lung bleeding.

Similar illnesses

Leptospirosis is easily confused with other fevers common in the same places:

Doctors in endemic areas often treat for leptospirosis while awaiting tests if the picture fits.

How leptospirosis is diagnosed

Always mention flood, freshwater, farm or animal exposure, and travel. Tests include:

• PCR on blood in the first week of illness, and on urine afterward
• Antibody tests (IgM ELISA), which become positive after about 5 to 7 days
• Microscopic agglutination test (MAT): the reference test, comparing antibody levels a week or two apart
• General tests: kidney and liver function, blood count (often low platelets), urine (protein and blood), muscle enzymes (often raised), and a chest X-ray if breathing is affected

Because antibody tests can be negative early, a negative first result does not rule it out.

Treatment

Antibiotics should start as early as possible, ideally within the first few days, without waiting for confirmation if the diagnosis is likely.

• Mild illness: oral doxycycline, or amoxicillin for children and pregnant women
• Severe illness: hospital treatment with intravenous penicillin, ceftriaxone or cefotaxime
• Supportive care: fluids, dialysis for kidney failure, oxygen or ventilation for lung involvement, and blood products for bleeding

A short-lived reaction with fever, chills and low blood pressure (Jarisch-Herxheimer reaction) can occur in the first hours of antibiotics. Kidney and liver function usually return to normal in survivors. Fatigue, low mood and eye inflammation can linger for weeks to months.

Prevention

• Avoid wading or swimming in floodwater or water that may be contaminated, especially with cuts or sores
• Cover cuts with waterproof dressings and wear waterproof boots and gloves for flood cleanup, farm work and gardening in wet soil
• Wash with clean water and soap after exposure
• Control rodents around homes and store food in sealed containers
• Vaccinate dogs; leptospirosis vaccines for dogs are widely available
• Drink only treated or boiled water when traveling
• High-risk travelers or workers are sometimes prescribed weekly doxycycline as short-term prevention; ask a travel medicine clinic

There is no human vaccine available in the US.

Frequently asked questions

How do humans get leptospirosis?

People catch it when water, mud or soil contaminated with infected animal urine touches cuts, scratches or the eyes, nose or mouth, or is swallowed. Flooding, freshwater sports, farming and rodent contact are the commonest routes. It almost never spreads from one person to another.

What are the first symptoms of leptospirosis?

The first symptoms, usually 5 to 14 days after exposure, are sudden fever, chills, severe headache, muscle aches that are worst in the calves and lower back, and red eyes without discharge. Vomiting and diarrhea are also common. It often resembles flu or dengue at first.

What is Weil's disease?

Weil's disease is the severe form of leptospirosis. It causes jaundice, kidney failure and bleeding, sometimes with life-threatening bleeding into the lungs. It needs hospital treatment with intravenous antibiotics and often dialysis or intensive care. It affects a minority of people with symptomatic infection.

Can you get leptospirosis from your dog?

Yes, though it is uncommon. Infected dogs shed the bacteria in urine. Avoid contact with a sick dog's urine, wear gloves when cleaning up, wash hands well, and keep your dog vaccinated. Dogs often catch it from puddles, ponds and rodent contact.

Is leptospirosis curable?

Yes. Antibiotics cure leptospirosis, and most people recover fully, especially when treatment starts early. Severe cases need hospital care for kidney, liver or lung complications, and some people feel tired for weeks to months after recovery.