Biological weapon
A biological weapon or bio-agent was a weapon that operates by spreading a pathogen such as a virus or a bacterium to the intended targets. This weapon is generally either lethal or at least physiologically devastating to those afflicted.

Malcolm Reed told General Gosis a lie during the interrogation when he said he and Captain Jonathan Archer were genetically enhanced and their immune systems were resistent to chemical and biological weapons. ()

On Earth, the use of biological weapons was outlawed by the Geneva Protocol of 1928 and 2155. ()

The Tarellian civilization was wiped out by biological weapons during a civil war, leaving a small number of plague-carrying survivors who escaped, typically infecting the populations of other planets after establishing contact. ()

The Dominion at times used biological weapons to make examples of populations that resisted their rule, including the Teplans, afflicted with the blight, and the inhabitants of Boranis III. ()

In 2373, upon initially seeing a Species 8472 bio-ship, Commander Chakotay speculated that it was either a space-dwelling organism or biological weapon. ()

In a holoprogram titled The Voyager Encounter, the Emergency Medical Android had examined the Kyrian genome and determined they would be vulnerable to any number of biological weapons. The Emergency Medical Android later established a datalink between his neural net and the phaser array of the warship Voyager to reconfigure the phaser beam to carry a bio-agent into the atmosphere of the Kyrian and Vaskan homeworld for the targeting of Kyrian cities. This attack caused 3,000 Kyrian deaths, however the fatality rate would be 300,000 in one hour as the bio-agent was still dispersing through the atmosphere. The death toll could've been much higher had there not already been an evacuation taking place which resulted in thousands of lives being saved. ()

In 2375, Species 8472 accused the  of having created biological weapons and infecting their species. In addition they accused Voyager off allying with the Borg. ()

The Brunali created a spaceborne virus that they then used to infect the Borg via children they deliberately allowed to be assimilated. Icheb was one such child, who (unknowingly) successfully transferred the virus to the Borg cube that assimilated him, killing all of the crew except for those Borg drones still in their maturation chambers. ()

See also 
 Biogenic weapon

External link 
 
Biology
Weapons