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What is Leptospirosis? Why is it on the Incline in Philippines?

Summary: Leptospirosis is a zoonotic illness that is caused by contact with contaminated water. It causes a non-localized febrile syndrome in those infected. The Department of Health in the Philippines recently reported a 13% rise in the cases of leptospirosis over the last 6 months from the same time period in 2020. Outbreaks generally occur in the July to October month, corresponding to the typhoon season. Prior outbreaks coincided with flooding. The article will cover the epidemiology, infection, and ways to prevent it.

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Leptospirosis Introduction

On September 26, 2009, Metro Manila faced the aftermath of severe flooding after a typhoon. Cases of the water-borne, animal-spread disease leptospirosis increased for the following month. From 15 hospitals in Manila, there were a total of 2,299 patients involved in the outbreak, with 178 deaths.

From January to June of 2021, Health Undersecretary Maria Rosario Vergeire reported a spike in leptospirosis cases compared to the same time in 2020 (589 compared to 520). So far, the case fatality rate is one in ten (11.4%). This is not the first year that this has occurred in the Philippines, with 40 to 60% rise in cases in 2018 most recently and 1,030 cases and 99 deaths.

What is Leptospirosis, why does it mainly cause infection in the Pacific Islands and other island countries? What are ways to prevent this infection and how can health officials address the disease burden?

More About Leptospira

Leptospirosis is caused by a spirochetal (spiral) bacteria in the genus Leptispira. The most common species that causes disease is L. interrogans group (e.g. L. icterohemorrhagiae.)

Leptospirosis is caused by the spirochaete Leptospira species.
A scanning electron micrograph(SEM) of Leptospira atop a 0.1 um polycarbonate filter. Photo source CDC/Rob Weyant. Wikimedia Commons.

Leptospirosis Epidemiology

The CDC estimates that 1 million cases of Leptospirosis occur globally, accounting for nearly 60,000 fatalities. The Pacific Islands Countries and Territories have the highest amount of leptospirosis cases. Seychelles is a country with one of the greatest rates of leptospirosis (432.1 per million population). Additionally, countries in the Pacific Ocean, including Australia and New Zealand, eastern Europe and Russia, and parts of Latin America and South America have high incidence rates. Cases have been reported in United States (100-150 cases/year, 50% from Hawaii) and Puerto Rico.

Caseloads worldwide of leptospirosis; Red is associated with the highest case loads.
Global annual incidence of human cases of leptospirosis. Highest to Lowest (Red, Pink, Green Yellow). Source: Pappas et al, 2008. Open Archive Files.

Leptospirosis is a zoonotic infection, meaning that it is associated with animals. It is a water and soil-borne infection. The disease is often associated with livestock management and human behavior (e.g. occupational risk, etc.). Within urban centers, rodents (rats) are significant Leptospira carriers. However, domestic animals, including cattle, pigs, horses, and dogs also are reservoirs. A prevalence study (2017) in the Philippines determined that Leptospira seropositivity in animals was high: 58% in slaughtered animals, 61.7% in pigs, and 33% in cows.

Heavy rainfall and flooding has lead to outbreaks (CDC Fact Sheet). Other reasons for leptospirosis cases include poor city planning (e.g. sewer systems), rapid urbanization, and garbage collection problems, allowing for rodent overpopulation.

Leptospirosis may be an occupational risk for farmers, miners, and sewage workers. It has also been acquired in recreational activity, such as hiking and white water rafting, and triathlons.

People make contact with urine-contaminated water and soil, either with the skin through intact skin, cuts, or abrasions or mucosal surfaces.

Leptospirosis Clinical Presentation

About 90% of infections are mild and nonspecific febrile illnesses. Mild leptospirosis is usually difficult to discern from other infectious causes, like influenza. A patient may have flu-like symptoms with fever, chills, headache, and body aches. It is unlikely that patients with milder cases would seek care or be tested for leptospirosis.

However, leptospirosis may present with a biphasic illness, with an inflammatory phase known as Weil’s disease, following the original, mild illness in 10% of cases. Symptoms can be severe and include shock, jaundice, acute kidney failure, and lung hemorrhaging. This is life-threatening and accounts for a case fatality rate (CFR) around 10%.

Diagnosis can be sometimes difficult, particularly in the beginning of the disease. It is made from bloodwork by detecting antibodies (IGM-based assays). A test to confirm usually follows, such as Microscopic agglutination test (MAT) or polymerase chain reaction (PCR) of blood, urine, or cerebrospinal fluid.

Leptospirosis can present with conjunctival suffusions and scleral icterus.
Conjunctival suffusions (bleeding) (scleral icterus also pictured) is a distinct clinical finding in leptospirosis. Source: Daniel Ostermayer, Wikimedia Commons.

Leptospirosis Treatment

The bacteria is quite sensitive to doxycycline and penicillin. Although most cases are mild and self-limited. Early treatment with antibiotics is beneficial in patients with a significant enough illness to seek care. While studies have not clearly shown a mortality benefit, earlier treatment was associated with a decreased likelihood to developing severe disease in some cases.

Ways to Prevent Disease

With an infection that can be fatal in approximately one-tenth of patients presenting with illness, the CDC recommends the following to prevent leptospirosis:

  • As the disease is transmitted in animal urine-contaminated water and soil, avoid fresh water or wet soil contact This includes swimming, drinking, or walking through water from rivers, ponds, or lakes.
  • Good protective shoes would reduce contact with water and wet soil. Avoid walking outside barefoot.
  • Take care of any cuts or scratches by using waterproof band-aids.

For prevention, 200mg of doxycycline may be taken weekly starting before exposure and through the exposure time. This is generally not recommended and used in select people that may have high-risk exposure, including the exposures mentioned above. Doxycycline can also be used as post-exposure prophylaxis, for people associated with cases identified in a high risk setting, such as wading in flood waters. Check out the Statement (2009) by the Philippines Society for Microbiology on Doxycycline here.

Leptospirosis control

Since many animals become harbor the bacteria, usually without any harm to the animal, it can be challenging to control leptospirosis. These animals may shed bacteria in the urine for a long time, even up to years. Additionally, the bacteria is hardy and can persist in water, soil, and mud for months.

With the typhoon season also comes an increased risk of dengue fever and other mosquito-borne infections.

gray mice in the middle of walls
Photo by David Bartus on Pexels.com

Situation in the Philippines:

At this point, it is early in the typhoon season which spans the next few months. Although cases are not as high as those reported in 2018 in the Philippines after flooding, it is still important to treat this increase as a potential threat the population. The Philippines is also potentially in the midst of an increased COVID-19 caseload.

Here are a few recommendations to reduce spread of Leptospirosis

  1. Ensure regular garbage collection to reduce a food source for rodent populations.
  2. Control the rodent population, particularly in high risk areas (areas with improper sewer systems, poor city planning, and waste management challenges).
  3. Educate the public regarding management of wounds (water-proof bandages), the importance of footwear, garbage control, and what Leptospirosis is (such as in this article).

For more information about zoonotic infections and outbreaks, check out this Your Health Forum link.


Amilasan A, Ujiie M, et al. Outbreak of Leptospirosis after Flood, the Philippines, 2009. 2012. Emerging Infectious Diseases. 18(1) Link. Accessed 7/31/2021.

CDC. Leptospirosis Fact Sheet for Clinicians. Link.

Goarant C. Leptospirosis: Risk factors and management challenges in developing countries. 2016. Res Rep Trop Med. Sep 28, 7: 49-62. doi: 10.2147/RRTM.S102543. Accessed 7/31/2021.

Pappas G, Papadimitriou P, Siozopoulou V, et al. The globalization of leptospirosis: worldwide incidence trends. 2008. International Journ Infect Dis. 12(4): 351-357. Accessed 7/31/2021.

Tabo N, Villanueva S, Gloriani N. Prevalence of Leptospira-agglutinating Antibodies in Abattoir Workers and Slaughtered Animals in Selected Slaughterhouses in Cavite, Philippines. Philippine Journal of Science. 2018. 147(1): 27-35. Link. Accessed 7/31/2021.

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