Why Are More People Getting Leptospirosis (Rat Fever) During the Monsoon, and How Can You Protect Yourself?

More people get leptospirosis during the monsoon because heavy rain causes flooding and waterlogging, which mixes with rodent urine and spreads Leptospira bacteria through contaminated water and soil. According to a report published by The Indian Practitioner, Kerala alone recorded 3,259 confirmed cases and 209 deaths between January and December 2025. Wading through floodwater with open cuts, working in wet fields, or walking barefoot in stagnant water are the main ways people get infected.

Key Takeaways

• Leptospirosis symptoms usually appear within 2 to 14 days and include fever, headache, muscle pain and calf pain
• Contaminated water, contaminated soil and rodent urine are the primary sources of infection during monsoon flooding
• Skin cuts and wounds allow the bacteria to enter the body far more easily
• Leptospirosis treatment works best when started early, usually with appropriate antibiotics prescribed by a doctor
• Leptospirosis prevention involves avoiding floodwater exposure, wearing protective footwear, and taking preventive doxycycline when advised by a doctor
• Kerala and Tamil Nadu together account for a large share of India's confirmed cases each year

Introduction

Every year, once the monsoon sets in, hospitals across South India start seeing a familiar pattern. Fever cases climb, and among them, a fair number turn out to be rat fever, more formally known as leptospirosis. This happens because rainwater mixes with soil, drains, and puddles that carry traces of rodent urine, and that combination becomes the perfect route for infection. This blog explains why rat fever during monsoon becomes such a recurring concern, what leptospirosis symptoms look like, and how you can lower your risk. If you are experiencing unexplained fever after wading through floodwater, our team at EMC Hospital can help you get tested and treated promptly.

Why Leptospirosis Cases Rise During Monsoon?

Infected rats, along with other infected animals like cattle and dogs, carry Leptospira bacteria in their kidneys and pass it out through urine. During dry months, this urine sits on soil and dries up, posing little threat. But once the monsoon flooding begins, everything gets washed together into puddles, ditches and stagnant water that people walk through daily.

India's numbers reflect this seasonal spike clearly. The country reported 14,222 confirmed cases in 2023, 19,005 in 2024, and 19,095 in 2025, and a large share of these clusters within just a few months. In fact, research from state surveillance data in Maharashtra and Tamil Nadu found that over 85% of annual leptospirosis cases in India occur during the monsoon and the months immediately following it.

The Climate Factor

Weather patterns have also been shifting in ways that don't help matters. A 2025 review published by The Week pointed out that monsoons are becoming less predictable, with delayed onset, shorter duration but heavier rainfall events, all of which extend the window during which people are exposed to contaminated water.

Leptospirosis Causes and How Infection Spreads

At its core, leptospirosis is caused by a corkscrew-shaped bacterium that thrives in warm, wet environments. Understanding leptospirosis causes helps explain why prevention is so heavily tied to water and soil hygiene.
The bacteria enter the human body through:

• Skin cuts and wounds that come into contact with infected water
• Mucous membranes such as the eyes, nose or mouth
• Prolonged soaking of skin in contaminated water or mud, even without a visible cut

Farmers, sanitation workers, fishermen and anyone wading through floodwater face the highest exposure. Even a small scratch on the foot can become an entry point if you're standing in stagnant water for long periods.

Leptospirosis Symptoms to Watch For

Leptospirosis symptoms often get mistaken for a regular viral fever early on, which is part of why the disease is so easy to miss. Usually, symptoms show up between 2 and 14 days after exposure.

Early Symptoms

• Sudden high fever
• Headache, sometimes severe
• Muscle pain, particularly calf pain
• Chills
• Red eyes
• Nausea or vomiting

When It Gets Serious

If left untreated, leptospirosis can progress into a more dangerous phase affecting the kidneys, liver, or even the lining around the brain. Health authorities in Kerala have noted that without timely antibiotics, people can develop serious kidney or liver complications, and in some cases the infection can be fatal. This is exactly why calf pain paired with fever after monsoon flooding shouldn't be ignored, even if it seems mild at first. 

Leptospirosis Treatment Options

Leptospirosis treatment is usually straightforward when started early. Doctors commonly prescribe antibiotics such as doxycycline or penicillin, depending on the severity of the case and how early the patient seeks care.

Mild Cases

Oral antibiotics taken over a short course, along with rest and fluids, are often enough to clear the infection without complications.

Severe Cases

Patients with worsening symptoms, kidney involvement or breathing difficulty may need hospital admission for intravenous antibiotics and closer monitoring. This is why doctors keep repeating the same advice: don't wait out a fever after floodwater exposure, get it checked instead.

Leptospirosis Prevention: Practical Steps

Leptospirosis prevention doesn't require anything complicated. Most of it comes down to reducing contact with contaminated water and soil, especially if you have any open wounds.

At Home

• Cover any cuts or wounds with waterproof dressings before stepping outdoors
• Avoid walking barefoot through puddles or waterlogged streets
• Keep food and water storage areas rodent-free
• Clean surfaces that may have come into contact with floodwater

At Work or Outdoors

• Wear gumboots and gloves if your work involves fields, drains or floodwater
• Wash hands and feet thoroughly with soap after any contact with stagnant water
• Take preventive doxycycline if advised by a doctor, particularly if you're in a high-exposure occupation

Community Level

Local authorities also play a role through rodent control programmes and drainage maintenance, which several studies have flagged as an area needing far greater investment rather than relying only on seasonal awareness campaigns.

Leptospirosis vs Common Monsoon Fevers

Who is at Higher Risk

Certain groups face a considerably higher chance of infection:

• Farmers and agricultural workers who wade through fields
• Sanitation and sewage workers
• People in low-lying areas prone to waterlogging
• Anyone with open wounds who comes into contact with floodwater
• Fishermen and those handling animals regularly

Conclusion

Leptospirosis follows a fairly predictable pattern tied to rainfall, contaminated water, and rodent activity, which is exactly why cases spike every monsoon. Recognising leptospirosis symptoms early, understanding leptospirosis causes, and following basic leptospirosis prevention steps can make a real difference in outcomes. If fever and calf pain show up after floodwater exposure, don't wait for it to pass on its own.

Frequently Asked Questions (FAQs)

Q1: How long does it take for leptospirosis symptoms to appear after exposure?
A1: Symptoms usually appear within 2 to 14 days after contact with contaminated water or soil, though 7 to 10 days is the most common window.

Q2: Can leptospirosis spread from person to person?
A2: No, leptospirosis does not spread directly between people. Infection happens through contact with contaminated water, soil, or rodent urine, not through coughing, touching, or close contact with an infected person.

Q3: Is leptospirosis fully curable?
A3: Yes, leptospirosis is fully curable, especially when antibiotics are started early. Most people recover completely with proper treatment. Delayed treatment increases the risk of kidney or liver complications, so early diagnosis matters.

Q4: Should I take antibiotics before entering floodwater to prevent leptospirosis?
A4: Preventive doxycycline is sometimes recommended for people with high exposure risk, such as rescue workers or those in flood-affected areas, but this should only be taken under medical advice rather than self-prescribed.

Get Checked 
If you have been exposed to floodwater or stagnant water this monsoon and are experiencing fever, headache or calf pain, don't wait to see if it passes. Reach out to EMC Hospital for quick diagnosis and treatment, our team is equipped to manage leptospirosis cases at every stage.

2026-08-20