Crimean-Congo hemorrhagic fever | Nairovirus
Crimean-Congo hemorrhagic fever most often infects goats and sheep, but people can contract the virus from ticks or the bodily fluids of infected animals. The fever is marked by the quick onset of gruesome symptoms, beginning with nausea and headache, and followed by bleeding within internal organs and underneath the skin as the virus attacks the body’s tissues.

Anthrax | Bacillus anthracis
The anthrax bacterium has had a long and relatively successful history as a tool of bioterrorism. In World War I, German agents in the U.S. reportedly infected American battleground-bound horses with it. In 2001, a series of contaminated letters killed five people in the U.S. and paralyzed the postal service. Anthrax spores are hardy, surviving for long periods in almost any environment.

Botulism | Clostridium botulinum
Botulinum toxin, produced by common soil-dwelling bacteria, is one of the most poisonous known substances–as little as 100 nanograms can kill an adult by disrupting nerve impulses. The U.S. sees sporadic outbreaks of foodborne botulism, usually caused
by eating improperly canned foods, but terrorists could intentionally contaminate the food supply with the toxin.

Glanders | Burkholderia mallei
In a single year in the 1980s, the Soviet Union’s bioweapons program reportedly produced more than 2,000 tons of the bacteria. Ordinarily, glanders resides in horses and rarely infects people. But if dispersed as an aerosol, it is a dangerous weapon. Even with antibiotic treatment, glanders has a 50 percent mortality rate; only a few bacteria are needed to trigger a deadly respiratory infection.

Ebola | Filoviridae ebolavirus
Thanks in part to sensationalist Hollywood fare such as Outbreak, but no doubt also because of the disease’s incredible near-80 percent mortality rate, Ebola is one of the best known and most feared bioterrorism threats. Since it first appeared in 1976, it has caused epidemics across Africa. Ebola effects a total meltdown of the
victim’s internal organs. There is no vaccine.

Smallpox | Variola major
One of the deadliest infectious diseases, smallpox killed some 500 million people in the 20th century alone before it was eradicated by a worldwide vaccination campaign. Today only frozen samples of the virus exist. If smallpox were ever to get out into the human population again, victims would experience a suffocating rash of pus-filled lesions, and as many as half of them would die.

Typhoid fever | Salmonella typhi
In the early 1900s, New York cook Typhoid Mary sickened at least 51 people by refusing to wash her hands before handling food. Since then, anti- biotics and hygiene have largely eradicated the disease in the U.S. But typhoid fever remains common in the developing world, causing 16 million illnesses and 600,000 deaths every year. The bacterium is now resistant to most drugs.