There may be a connection between climate change, primarily increased extreme precipitation, and rising cases of waterborne disease outbreaks in Sweden and other European countries. In northern Europe, assessments have indicated that precipitation volumes will increase, which will adversely affect the raw water quality, the preparation process and the distribution of drinking water. The most common infectious agents have been Campylobacter and Norovirus. According to the Swedish Center for Decease Control, it seems that the number of cases is already increasing, which may be associated with a slightly warmer climate. Waterborne diseases anticipated to increase due to climate change are those caused by viruses, and protozoa such as Cryptosporidium. These are considered to be severely under-diagnosed today and the number of diagnosed cases in Sweden is expected to increase. Serious problems with raw water quality, preparation and distribution usually appear by clusters of disease cases. Only a small part of the disease cases are probably detected and reported to the authorities. Waterborne disease outbreaks can affect people through contaminated water sources, incorrect wiring in waterworks or through leaks in distribution networks. The drinking water is a very fast and efficient carrier of infectious agents. Raw water contaminated with microorganism from human or animal feces is the most common cause of outbreaks due to drinking water. The need of early warning systems and rapid identification methods is great since the agent causing the disease remains unknown in a large share of all waterborne outbreaks. From a safety and security perspective, it is a serious shortcoming and initial attempts have been made to develop rapid detection and specific analytical methods that can measure the levels of potential pathogenic microorganisms. The drinking water is vulnerable when burglary and active acts of sabotage can affect any part of the drinking water supply chain. In particular, the raw water sources and the distribution grid are hard to protect. IT-controlled water utilities can also be subjected to hacking and virus attacks.