The supply of drinking water is a crucial and vulnerable element of the Swedish infrastructure. In the past few years it has suffered several crises due to contamination and waterborne diseases. Therefore, management of water crisis has become a highly topical issue for the country's municipalities, particularly after two recent outbreaks of cryptosporidium. This protozoan parasite is often spread through contaminated water and causes a parasitic disease that affects the intestines and typically causes an acute short-term infection. The largest known outbreak of cryptosporidium in drinking water occurred in 1993 in Milwaukee, US, where more than 400 000 people were infected. In Sweden, two large outbreaks have occurred during the past few years. The drinking water in Östersund, a mid-sized city with around 59 000 inhabitants, was infected with cryptosporidium in November 2010. The number of people infected reached approximately 27 000, and the outbreak lasted for 12 weeks. Just a few months afterwards, Skellefteå, with 71 000 inhabitants, had a similar experience. At least 20 000 people were infected in an outbreak lasting 20 weeks. This type of crisis affects many people for a long time, and effective communication, therefore, is essential to limit the impact of the crisis.