1. Department of Communicable Disease Prevention and Control, Region Västra Götaland, Sweden
2. Department of Infectious Diseases, Sahlgrenska University Hospital, Göteborg, Sweden
3. Department of Paediatrics at the Queen Silvia Children’s Hospital, Sahlgrenska University Hospital, Göteborg, Sweden
4. Department of Virology, Sahlgrenska University Hospital, Göteborg, Sweden
5. Department of Obstetrics and Gynaecology, Sahlgrenska University Hospital, Göteborg, Sweden
6. Department of Hospital Infection Control, Sahlgrenska University Hospital, Göteborg, Sweden
7. Department of Virology, Swedish Institute of Infectious Disease Control, Stockholm, Sweden