A biological hazard, or biohazard, is anything coming from living organisms (i.e. pollen, fungi, animals, insects, bacteria and viruses) that could be a threat to someone's health. It is represented by ☣, the biohazard symbol, which is used everywhere in the world. When people see this sign they know to take precautions, and to follow proper conduct for science labs.

There are four biosafety levels made by the Center of Disease Control. These are used in laboratories so only people who have the right skills can enter. Different levels mean scientists must wear different uniforms and take special care when dealing with dangerous things like viruses.^[1]

Biosafety Level 1 The viruses handled in BSL-1 are not very dangerous and usually only cause mild sickness. Diseases in BSL-1 include chicken pox and some E-Coli strains. People in BSL-1 have to wash their hands with soap, wear gloves, and put waste materials in specially-marked bins.

Biosafety Level 2 BSL-2 is filled with slightly more hazourdous diseases than BSL-1. They have to take more safety precautions has a result. Hepatitis, influenza, HIV / AIDS, and salmonella are handled here.

Biosafety Level 3 BSL-3 is for diseases that may kill but are less deadly than those in Level 4, SARS and yellow fever. A lot of them are airborne, and the lab must be in an closed off area in case of an incident.

Biosafety Level 4 BSL-4 is for very hazardous diseases that kill many people and are hard to treat. BSL-4 workers must be careful and alert at all times and wear suits with special air filters. A lot of hemorrhagic fevers are dealt with in BSL-4, like Ebola, Marburg, and Lassa Virus.