Three of the people who were infected had visited the Urkult festival in Ångermanland from July 30 to August 1 this year.
"People who visited the festival should be aware of symptoms of measles in themselves and their loved ones and contact healthcare by telephone if they suspect the disease. This is especially important for those who have not been vaccinated against measles," the Public Health Agency writes in a press release.
The agency is now working with regional infection control units to reduce the risk of further spread of infection.
Measles is a highly contagious disease that can cause serious illness. The disease is uncommon in Sweden, as it is included in the vaccination program for children.
"Two doses of measles vaccine provide very good protection against the disease. Since such a large part of the population is vaccinated, the risk of major outbreaks is low," says Johanna Rubin, a doctor at the vaccination program unit at the Swedish Public Health Agency, in the press release.
Measles usually first causes symptoms such as a dry cough, itchy and red eyes that are sensitive to light, and a high fever. After a few days, a rash appears, which is usually first noticed on the face and then spreads to the rest of the body.
"If you need to seek care, it is important to call first and not go directly to a clinic," writes the Public Health Agency.
