THIRUVANANTHAPURAM: Despite Kerala having a robust healthcare infrastructure, rat fever (leptospirosis) has emerged as the state’s most lethal infectious threat, with related deaths skyrocketing to 1,455 between 2021 and 2025.
Alarmingly, the disease saw a three-fold jump in case volumes over those five years, alongside a spike in its mortality rate to a worrying 6%.
Yet, while public anxiety and administrative focus remain overwhelmingly consumed by high-profile outbreaks of dengue and localised scares of shigellosis, this far more dangerous killer is failing to receive the critical attention and resource allocation it urgently requires.
This deficit in public health prioritisation has extended directly into the current year, with fresh data from the directorate of health services (DHS) revealing that the state has already recorded 1,531 cases and 56 deaths as of June 23, 2026.
While the catastrophic floods of 2018 and 2019 served as the initial ecological triggers for this crisis, the true scale of the explosion was temporarily masked by the Covid lockdowns, which restricted public movement and minimised environmental exposure.
However, once normalcy returned in 2022, annual cases abruptly quadrupled to over 5,000 cases per year, signalling a dangerous post-disaster shift that the state’s public health machinery has failed to adequately address due to its preoccupation with more visible vector-borne and food-borne pathogens.
Medical professionals warn that this lack of administrative focus is particularly hazardous because the disease’s epidemiological and clinical profile has fundamentally altered, catching clinicians off guard while attention is diverted elsewhere.
“Earlier, most of the patients were field workers. Now, the cases are found among other categories as well,” said Dr Althaf A, an epidemiologist and professor at the Government Medical College, Thiruvananthapuram.
Dr Althaf pointed out that the disease is now being detected even among bedridden patients who have minimal contact with the outside environment, indicating a much wider, insidious environmental contamination. Furthermore, the clinical window for intervention has shrunk dramatically, making early suspicion vital.
While complications traditionally manifested after a week or two, patients are now experiencing severe organ complications and rapid deterioration by the third or fourth day of fever.
To counter this rapid progression, experts argue that cases must be aggressively picked up during initial outpatient consultations based on clinical symptoms alone, allowing for the immediate administration of doxycycline on Day One.
This matches guidelines from the High-Power Committee for Epidemic Control, which recommends immediate doxycycline use alongside distributing protective gloves and boots to agricultural and manual labourers.
The persistent surge and corresponding policy neglect also expose a critical systemic failure in post-disaster vector control and animal surveillance, which traditionally prioritises mosquito eradication to fight dengue over complex rodent control strategies.
“During floods, rodents get washed off, and their urine and excretion lead to widespread sewage contamination,” said Dr S Nandakumar, assistant director, animal husbandry department.
However, tracking and proving the exact transmission routes remains an uphill task because rodents are classified as agricultural pests rather than domestic animals under veterinary care, leaving them out of routine health monitoring. Dr Nandakumar noted that establishing a definitive epidemiological link requires laboratory-backed serovar profiling to match the bacteria in animals to human cases.
Because rodents are the most populous mammalian species, controlling them post-disaster is an immense practical hurdle that requires dedicated institutional will.
Alarming numbers
2011 to 2015: 4,667 cases and 208 deaths (mortality rate: 4.5%)
2016 to 2020: 7,447 cases and 319 deaths (mortality rate: 4.2%)
2021 to 2025: 23,953 cases and 1,455 deaths (mortality rate: 6%)