Apart from SARS and Covid-19, there will be other outbreaks. In the future, there will also be a type of waterborne pathogen that is capable of consuming flesh, making water unsafe for human consumption and affecting marine life.
This waterborne pathogen will be unleashed from glaciers and ice caps as they melt, reviving the pathogen and turning them active once in the water. They can survive temperatures of 80 - 100°C or even higher, thus possibly rendering boiling an ineffective means to disinfect water. Moreover, this pathogen will spread through the water cycle, eventually finding itself in rainwater too. The degree to which this pathogen will spread is unprecedented and make everyone fearful of drinking water.
When that happens, Governments worldwide will add chemical disinfectants to water, however, overexposure to such chemicals will harm the human body.