The School of Tropical Medicine (STM) has confirmed the presence of fecal coliform bacteria in samples collected from the current diarrhoea belt in Kolkata. The confirmation came a couple of days after KMC admitted to water contamination.The water samples had been collected from Patuli, Bagha Jatin, Santoshpur, Mukundapur, Kasba and Garfa areas and sent to STM for examination. The tests have confirmed presence of virulent strain of E.coli that triggers diarrhoea.

Pathogenic E. coli make toxins which damage the lining of the intestine. The strains of E. coli that make the toxin are sometimes called STEC, which is short for “Shiga toxin-producing E. coli.” These cause abdominal cramps, vomiting, and in some cases bloody diarrhoea. Sometimes, the bacteria can invade the intestinal wall itself, which results in the toxin spilling into the blood stream. In such cases, it could cause renal damage and multi-organ failure

Enteric diseases happen when the fecal E-coli mix with the municipal supplies. There can be many reasons for the same and Kolkata Municipal Corporation will fund out the source of contamination. Treating the enteric cases will not solve the root cause.

Infiltration: In this situation contaminated sub-surface water is drawn into the distribution system. In order for this to happen three conditions must be in place. First contaminated water must be present in the sub surface possibly from leaking sanitary, storm or combined sewer. Secondly, there must be an adjacent low-pressure zone in the water supply pipe either due to high water use or pressure surges in the water supply system and thirdly there must be a pin hole caused by corrosion, cracks or outright breaks or leaking joints in the wall of the water mains. This leads to intrusion of pathogenic organisms in the water supply system.

Back Siphonage: In this situation faecally contaminated surface water is drawn into the distribution system or storage reservoir through a back flow mechanism.

Open drinking water storage reservoirs: Microbial contamination can be introduced into the distribution system through open treated-water storage reservoirs.

Line construction and repair: When existing mains are repaired or replaced or when new water mains are installed strict protocols if not followed involving disinfection and flushing can lead to contamination and debris into the drinking water supply system.