A biological hazard or biohazard is an organism, or substance derived from an organism, that poses a threat to (primarily) human health. This can include medical waste or samples of a microorganism, virus or toxin (from a biological source) that can impact human health. It can also include substances harmful to animals. The term and its associated symbol is generally used as a warning, so that those potentially exposed to the substances will know to take precautions. There is also a biohazard HCS/Workplace Hazardous Materials Information System (WHMIS) logo which utilizes the same symbol.
In Unicode, the biohazard sign is U+2623 (☣).
Biohazardous agents are classified for transportation by UN number: