Anyone who went to Paris to watch the Olympics are being asked not to donate blood in Switzerland for the next few weeks.
There are concerns about viruses circulating – especially chikungunya, which is a disease spread by the tiger mosquito.
Nathalie Rufer, head of the transfusion centre in Epalinges in Vaud says there’s an epidemic in Paris at the moment.
Donors are being asked to stay away for at least a month.