WHO focuses on the possible public health consequences of an incident, regardless of whether it is characterized as a deliberate act or a naturally occurring event. 

When a Member State is concerned and wants to be prepared, WHO advises strengthening public health surveillance and response activities, with an emphasis on: 

Biological weapons are microorganisms like virus, bacteria, fungi, or other toxins that are produced and released deliberately to cause disease and death in humans, animals or plants. 

Biological agents, like anthrax, botulinum toxin and plague can pose a difficult public health challenge causing large numbers of deaths in a short amount of time while being difficult to contain. Bioterrorism attacks could also result in an epidemic, for example if Ebola or Lassa viruses were used as the biological agents.