How the impact of Covid-19 on a contractual relationship is dealt with under Swiss law depends primarily on the language of the contract. If it contains a specific "force majeure" clause dealing with a pandemic, that clause applies. Of course, such explicit clauses have not been widely agreed prior to the pandemic. In this case the contract has to be construed in order to determine the intent of the parties, and the Swiss Code of Obligations (CO) applies if it is found that the parties have not made a provision dealing with the impact of a pandemic.