10 Scariest Bioweapons

Small pox

Smallpox is caused by the variola virus. The most common form of the disease has a 30 percent mortality rate [source: CDC]. Signs of smallpox include high fevers, body aches, and a rash that develops from fluid-filled bumps and scabs to permanent, pitted scars. The disease predominantly spreads through direct contact with an infected person's skin or bodily fluids, but also can be spread though the air in close, confined environments.

In 1967, the World Health Organization (WHO) spearheaded an effort to eradicate smallpox through mass vaccinations. As a result, 1977 marked the last naturally occurring case of smallpox. The disease was effectively eliminated from the natural world, but laboratory copies of smallpox still exist. Both Russia and the United States possess WHO-approved stores, but as smallpox played a role in several nations' bioweapons programs, it's unknown how many secret stockpiles still exist.

T­­he CDC classifies smallpox as a Category A biological weapon due to its high mortality rate and the fact that it can be transmitted through the air. While a smallpox vaccine exists, typically only medical and military personnel undergo vaccination -- meaning the rest of the population is very much at risk if smallpox were unleashed as a weapon. How might the virus be released? Probably in aerosol form or even in the old-fashioned wa­y: by sending an infected individual directly into the target area.

The method for unleashing a biological weapon doesn't have to be flashy, however.

Anthrax

Most cases of anthrax are cutaneous, transmitted through skin contact with the spores. The most deadly form is inhalation anthrax, when the spores travel to the lungs and then the immune cells carry them to the lymph nodes. Here, the spores multiply and release toxins that result in such symptoms as fever, respiratory problems, fatigue, muscle aches, enlarged lymph nodes, nausea, vomiting, diarrhea and black ulcers. Inhalation anthrax carries the highest mortality rate of the three (100 percent, 75 percent with medical treatment), and unfortunately, that was the form contracted by all five casualties from the 2001 anthrax letters [source: NPR].

The disease isn't easy to catch under normal situations, and it can't be transmitted from person to person. Still, health workers, veterinarians and military personnel normally undergo vaccinations. The rest of us, however, remain at risk if someone were bent on another anthrax attack.

Along with the lack of widespread vaccination -- a common theme among our scary bioweapon nominees -- longevity is another point in anthrax's favor. Many harmful biological agents can only survive a short while under certain conditions. But hardy B. anthracis can sit on the shelf for 40 years or more and still pose a lethal threat.

Ebola Hemorrhagic Fever

Another well-documented killer exists in the form of the Ebola virus, one of more than a dozen different viral hemorrhagic fevers, nasty illnesses sometimes marked by copious bleeding. Named for the region of the Congo in which it was first discovered, scientists suspect the Ebola virus normally resides within a native, African animal host, but the exact origin and natural habitat of the disease remain a mystery. As such, we have only encountered the virus after it has successfully infected humans or nonhuman primates.

Once present in a host, the virus infects others through direct contact with blood or other bodily secretions. In Africa, the virus has proved itself particularly adept at spreading through hospitals and clinics. An infected individual can expect to start experiencing symptoms in between 2 and 21 days. Typical symptoms may include headache, muscle ache, sore throat and weakness, followed by diarrhea and vomiting. Some patients also suffer internal and external bleeding. Between 60 and 90 percent of infections end in death after 7 to 16 days [source: Chamberlain].

Doctors don't know why some patients are better able to recover than others. Nor do they how to treat it. And, as noted earlier, there's no Ebola vaccine. In fact, we only process a vaccine for one form of hemorrhagic fever: yellow fever.

While many medical professionals labored to better treat and prevent outbreaks of Ebola, a team of Soviet scientists set out to turn the virus into a weapon. They initially encountered difficulties cultivating Ebola in the laboratory, enjoying more success with the development of Marburg hemorrhagic fever. By the early 1990s, however, they had solved the problem [source: ­Alibek]. While the virus normally spreads through physical contact with bodily secretions, researchers have observed it spread through the air under laboratory conditions. The possibility of a weaponized, aerosol form of the virus only further cements Ebola and related viral hemorrhagic fevers as permanent placeholders on the list of Category A agents.

The word "Ebola" is already synonymous with terror and death, despite having only become news in the last few decades.

Plague

Plague exists in two main strains: bubonic and pneumonic. Bubonic plague typically spreads by bites from infected fleas, but also can be transmitted from person to person through contact with infected bodily fluids. This strain is named for the swollen glands, or buboes, around the groin, armpit and neck. This swelling is accompanied by fever, chills, headache and exhaustion. Symptoms occur within two or three days and typically last between one and six days. Unless treated within the first 24 hours of infection, 70 percent of those infected die [source: Chamberlain]. Pneumonic plague is less common and spreads through the air by coughs, sneezes and face-to-face contact. Its symptoms include high fever, cough, bloody mucus and difficulty breathing.

Today, experts predict that plague would likely be weaponized in the form of an aerosol, resulting in an outbreak of pneumonic plague. However, low-tech, vermin-based attacks are still possible.

Several countries have explored the use of plague as a bioweapon and, as the disease still occurs naturally throughout the world, copies of the bacterium are relatively easy to come by. With appropriate treatment, plague's mortality rate can dip as low as 5 percent [source: BBC]. There is no vaccine.

A bioweapon doesn't have to boast a high mortality rate to be successful, though.

Tularemia

While tularemia only claims an overall 5 percent mortality rate, the microorganism that causes it is one of the most infectious bacteria on Earth . Francisella tularensis occurs naturally in no more than 50 organisms and is especially prevalent in rodents, rabbits and hares. Humans typically acquire the disease through contact with infected animals, infected insect bites, the consumption of contaminated foods or the inhalation of the bacteria in aerosol form.

Symptoms typically appear within 3 to 5 days and vary depending on the method of infection. Patients may experience fever, chills, headache, diarrhea, muscle aches, joint pain, dry cough and progressive weakness. Pneumonialike symptoms can also develop. If untreated, respiratory failure, shock and death can follow. The illness typically lasts less than two weeks, but during that time, the infected people are basically bedridden.

Tularemia doesn't transfer between human hosts and can be easily treated with antibiotics or prevented with a vaccine. It does, however, spread very rapidly between animal hosts and humans or when used in aerosol form. It is this factor, not its mortality rate, that earned F. tularensis a Category A biological weapon ranking. It is especially virile in aerosol form.

Botulinum Toxin

In weaponized airborne form, the deadly bacteria would be completely colorless and odorless. Between 12 and 36 hours later, however, the first signs of botulism would begin to take hold: blurred vision, vomiting and difficulty swallowing. If untreated, paralysis begins to take hold, seizing up your muscles and finally your respiratory system.

Without respiratory support, Clostridium botulinum can kill in 24 to 72 hours. For this reason, the o­rganism's deadly toxin rounds out the list of six Category A biological weapons. With ventilators to work your lungs, the mortality rate plummets from 70 percent to 6 percent, but recovery takes time [source: Chamberlain]. This is because the toxin binds to the point where nerve endings and muscles meet, effectively cutting off the signal from the brain. To recover fully from a case of botulism, the patient actually has to grow new nerve endings -- a process that takes several months. And while a vaccine exists, concerns over effectiveness and side effects have plagued its development, so it's not widely used.

As if the symptoms weren't scary enough, C. botulinum occurs all over the world, especially in soil and marine sediments. The spores often pop up on fruits, vegetables and seafood. In this state, they're harmless. It's only as they begin to grow that they produce their deadly toxin. Humans primarily encounter the toxin through the consumption of tainted foods, as the temperatures and chemicals in improperly stored foods often provide the perfect conditions for the spores to grow and develop. Deep wounds and infant intestinal tracks also present similar conditions.

Its power, availability and limited treatability have made botulinum toxin a favorite among several countries' bioweapons programs.

Rice Blast

A number of bacteria, viruses and toxins pose a significant threat to human beings, but plenty of the world's biological agents prefer different prey: cultivated food crops. Cutting off an enemy's food supply is a time-tested military strategy, whether you're defending your homeland against an invading force or besieging a walled city. Without food, populations weaken, panic, riot and eventually die.

One such bioweapon is rice blast, a crop disease caused by the fungus Pyricularia oryzae (also known as Magnaporthe grisea). The leaves of affected plants soon develop grayish lesions composed of thousands of fungal spores. These spores quickly multiply and spread from plant to plant, sapping the plants and leading to much lower crop production. While breeding resistant plants is a good defensive measure against some crop disease, rice blast presents a problem because you wouldn't have to breed resistance to one strain of fungus, but 219 different strains.

Such a bioweapon wouldn't be as sure of a killer as the likes of smallpox and botulism. It could however lead to severe starvation in poorer countries, as well as financial losses and other huge problems.

A number of countries have pursued rice blast as a biological weapon.

Rinderpest

Rinderpest is caused by a virus closely related to measles, and it affects cattle and other ruminant animals such as goats, bison and giraffes. The condition is highly contagious, causing fever, loss of appetite, dysentery and inflammation of the mucus membranes. The condition drags on for six to 10 days, when the animal typically succumbs to dehydration.

Over the centuries, humans have introduced rinderpest-infected animals to various corners of the globe, often resulting in millions of dead cattle, along with other livestock and wild animals.

Nipah Virus

Viruses adapt and evolve over time. New strains emerge and, occasionally, close contact between humans and animals allow life-threatening diseases to leap to the top of the food chain. As human populations continue to swell, the emergence of new diseases is inevitable. And every time a new outbreak makes the headlines, you can be sure someone is considering how to turn it into a weapon.

Nipah virus is just such a disease, having only risen to the attention of world health agencies in 1999. The outbreak occurred in the Nipah region of Malaysia, infecting 265 and killing 105. While 90 percent of those infected handled pigs for a living, health workers su­spect the virus naturally occurs in fruit bats. The exact nature of transference is uncertain, but experts think that the virus may spread through close physical contact or contaminated body fluids. Human-to-human transmission hasn't been reported yet.

The illness typically lasts 6 to 10 days, inducing symptoms that range from mild, flulike conditions such as fever and muscle pains to encephalitis, or inflammation of the brain. In these more severe cases, patients experienced drowsiness, disorientation, convulsions and ultimately coma. The virus carries a mortality rate of 50 percent, and there currently are no standard treatments or vaccinations [source: WHO].

Nipah virus, along with a number of other emerging pathogens, is classified as a Category C biological weapon. While no country is known to have researched its weaponization, its potential for widespread use and 50 percent mortality rate make it a bioweapon to watch for.

Chimera Viruses

In Greek and Roman mythology, the chimera combined elements of lion, goat and serpent into one monstrous form. Artists in the late medieval age often used the creature as a symbol to illustrate the complex nature of evil. In modern genetic science, a chimeric organism is a life form that contains genes from a foreign species. Given its namesake, you might expect all chimeric organisms to be awful examples of man twisting nature for nefarious ends. Fortunately, our increased understanding of genetic science has led to some beneficial creations. One such chimera, which combines the common cold with polio, may help cure brain cancer.

But as the war continues its forward momentum through human history, the abuse of such science is inevitable. Geneticists have already discovered the means to increase the lethality of such bioweapons as smallpox and anthrax by tweaking their genetic structure. By combining genes, however, scientists could theoretically create a virus that triggered two diseases at once. During the late 1980s, the Soviet Union's Chimera Project studied the feasibility of combining smallpox and Ebola into one super virus [source:Alibek].

Other potential nightmare scenarios involve strains of viruses that require certain triggers. A stealth virus would remain dormant for an extended period until triggered by predetermined stimuli. Other possible chimeric bioweapons might require two components to become effective. Imagine a strain of botulinum toxin that, when combined with the botulinum toxin antidote, only becomes more lethal. Such a biological attack would not only result in a higher mortality rate, but might erode public trust in health initiatives, aid workers and government response to the outbreak.

From splitting the atom to cracking life's genomic riddles, the last century of scientific research has brought about tremendous potential for humans to build a better world -- or destroy the one they have.

Credit to:Howstuff`s