Several chronic viral infections (such as HIV and hepatitis C virus) are highly prevalent and are a serious health risk. The adaptation of animal viruses to the human host, as recently exemplified by influenza viruses and the severe acute respiratory syndrome coronavirus, is also a continuous threat. There is a high demand, therefore, for new antiviral lead compounds and novel therapeutic concepts. In this Review, an original therapeutic concept for suppressing enveloped viruses is presented that is based on a specific interaction of carbohydrate-binding agents (CBAs) with the glycans present on viral-envelope glycoproteins. This approach may also be extended to other pathogens, including parasites, bacteria and fungi.