Swedish authorities announced on Thursday that frozen berries may have been the cause of over 20 Hepatitis A infections in Sweden since December.

The Swedish Institute for Communicable Disease Control (Smittskyddsinstitutet, SMI) warned that the berries may have been responsible for 22 cases of Hepatitis A in Sweden so far.

The usual contagion rate for the same timeframe is about five people in Sweden.

Experts from the institute advised berry lovers to take caution when consuming any berries bought in Sweden that were sold frozen.

“If you cook them for at least one minute then all the contagion will die or disappear,” Margareta Löfdahl, epidemiologist from the Institute, told the TT news agency.

The people infected in Sweden were infected with the same type of Hepatitis that 30 people in Denmark were diagnosed with recently, which has since been traced to frozen berries and strawberries in particular.