Well water key risk factor for amoebic meningitis in Kerala, ICMR study finds
A joint field study by the Kerala Health Department and the Indian Council of Medical Research's National Institute of Epidemiology in Chennai has identified the use of non-chlorinated well water for bathing and washing the face as a significant risk factor for amoebic meningoencephalitis (AME). This is the first epidemiological evidence from the State on potentially modifiable exposures linked to the disease, which can be fatal.
The case-control study, published in the journal Emerging Infectious Diseases, analysed 159 AME cases reported in Kerala between January 1 and November 11, 2025. Of these, 76 were confirmed by real-time PCR and 83 by microscopic examination of cerebrospinal fluid. Among the PCR-confirmed cases, 67 (88.2 per cent) were caused by Acanthamoeba species and nine (11.8 per cent) by Naegleria fowleri.
The study found that people who used well water for bathing or washing their face had 2.95 times higher odds of contracting AME. The estimated population attributable fraction was 34.2 per cent, meaning that more than a third of Acanthamoeba-caused AME cases in Kerala could be prevented if exposure to non-chlorinated well water were eliminated.
Dr. R. Aravind, head of infectious diseases at Thiruvananthapuram Government Medical College and a key researcher in the study, said: “The finding that the use of non-chlorinated water, or well water, for domestic purposes is independently associated with AME caused by Acanthamoeba is quite relevant for Kerala, where only a tiny fraction of the population has access to chlorinated, safe, piped water supply.” He also noted that the study provides the highest level of scientific evidence that water quality is a key public health issue requiring immediate investment.
The study distinguishes domestic water use — activities such as bathing or washing the face and hair that involve direct contact with the face, head, skin, or body — from ingestion. It does not refer to drinking water. Known risk behaviours such as diving into natural water bodies, snorting water into the nostrils, and entering water with skin wounds remain separate factors that increase susceptibility to AME.
Many households in Kerala depend on individual or public wells. Heavy rainfall, flooding, sewage contamination, organic matter, and algal growth can contribute to the contamination of poorly maintained wells and promote the proliferation of free-living amoebae. The study highlights that these conditions are prevalent in Kerala, making water quality surveillance and maintenance a year-round necessity.
Public health experts stress that local self-governments must invest in periodic chlorination and maintenance of wells to minimise risk. Public health messaging, particularly during the monsoon and post-monsoon periods, should focus on reducing high-risk exposures and encouraging the use of safe, treated water for facial and body washing.
The study, titled “Epidemiology of and Risk Factors for Amoebic Meningoencephalitis, Kerala 2025,” underscores that ensuring safe domestic water is not just a convenience but a critical public health measure. The findings call for urgent action to improve water quality infrastructure across the State.
