People in areas near rivers which have flooded in recent days are being warned that their homes may now be contaminated.
Flood waters can carry small particles of sewage and other toxins which can cause a number of diseases.
Dr Dougall Jerram from the University of Oslo says homeowners should replace any furniture which has been affected by flood water.
"To think that, you know, your house is flooded and you can just let it dry out and people will be move back in - but clearly that's not the case," he said.
"If flood water contains any small remnants of any of those horrible things, even dead rats and dead animals could be in the system, that's going to drip into the plasterboard, it's going to soak into any of the carpets and so on, so it all has to be replaced."