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How do water chlorination and milk pasteurization control diseases spread through water or milk?

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Diagram showing the West Nile virus transmission cycle: a mosquito bites an infected bird (the primary reservoir host), then transmits the virus to humans or horses (incidental hosts) through subsequent bites. — infectious disease Birds are the primary reservoirs of West Nile virus. The virus is transmitted to humans and horses by mosquitoes that have bitten infected birds.

Water chlorination and milk pasteurization are critical public health interventions that control the spread of infectious diseases by eliminating harmful pathogens.

Water Chlorination

Chlorination is a disinfection process used to ensure the safety of drinking water. By adding chlorine or chlorine compounds to water, treatment plants destroy pathogenic bacteria that cause waterborne illnesses, such as cholera. A key advantage of this method is that a residual concentration of chlorine can be maintained throughout the water distribution system, providing ongoing protection against contamination until the water reaches the consumer.123

Milk Pasteurization

Pasteurization is a heat-treatment process that destroys disease-causing microorganisms in milk without sterilizing it or significantly altering its nutritional value. By briefly heating milk to specific temperatures—such as 72 °C (162 °F) for 15 seconds—the process effectively kills pathogens like E. coli, Salmonella, and Mycobacterium tuberculosis. This practice has been instrumental in reducing milk-borne epidemics and protecting vulnerable populations from foodborne illnesses.45