Metallic silver has been used in various forms since the Middle Ages because of its disinfection effects. However, advances in the field of nanotechnology have allowed the revelation of the extraordinary potential and broad spectrum of antimicrobial properties of the finely dispersed silver nanoparticles known also as colloidal silver. The antibacterial properties of silver nanoparticles have been proved to be effective against a wide range of bacteria, including highly resistant strains (such as Staphylococcus aureus). The mechanisms of the effect can include damage and modification of the cytoplasmic membrane of bacteria, damage to bacterial DNA replication, etc. The smaller the nanoparticles, the higher their antibacterial activity. Nanosilver is also highly effective against fungi and mould. It is in many ways even more effective than commercial fungicidal agents. When compared with ionic silver (Ag+), silver nanoparticles (Ag0) are considerably less toxic to human cells. A number of studies have been published recently demonstrating the effectiveness of nanosilver in suppressing a wide range of viral infections, including the flu, herpes simplex, hepatitis B, HIV viruses, respiratory tract infections, rotavirus and coronavirus infections. Nanosilver acts as an antiviral through a number of potential mechanisms, including suppression of the virus replication in human cells. Medicines for the treatment of coronavirus infections (such as Remdesivir), including MERS-Cov and SARS-Cov2, are focused, among others, on the prevention of virus genome replication. Additionally, the survival period of viruses (including SARS) and bacteria on surfaces containing silver or those impregnated with nanosilver is considerably shorter on those surfaces. That is also why colloidal silver offers a huge application potential in medicine, in the antimicrobial treatment of surfaces and in disinfection technologies. Nanosilver is used for disinfection of water and air, as well as areas and products in the fields of medicine, veterinary care, the textile industry and the food processing industry.