BBCNews . 26 October
Anthrax anxiety has gripped America
Anthrax is not the only disease capable of being used as a biological weapon. Others such as smallpox, botulism and Ebola could also be used in an attack.
BBC News Online examines the symptoms and risks associated with some of those which could be used on humans.
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Botulism
What is it? Botulism is a muscle-paralysing disease caused by a toxin from the bacterium Clostridium botulinum. There are three main types - food-borne, wound and infant botulism.
Symptoms
The first recognisable symptoms, usually appearing 12 to 36 hours after exposure to the toxin, include blurred vision, vomiting and difficulty in swallowing.
If untreated, the disease can eventually lead to respiratory failure and paralysis. It is fatal in 5 to 10% of cases.
How is it spread?
Botulism is caused by eating or inhaling the bacterial toxin. It cannot be spread from person to person.
If used as a biological weapon, the toxin could be sprayed as an aerosol - it is colourless and odourless - or used to contaminate food.
Is there an antidote?
An antitoxin is available, but it is only effective if administered early in the course of the disease. There is also a vaccine, but concerns about its effectiveness and possible side-effects mean it is not widely used.
Availability
The bacterium from which botulism is derived occurs naturally in the ground, so many samples are likely to be held around the world. The Japanese cult Aum Shikrikyo dispersed it in aerosols on at least three occasions in the early 1990s. According to John Eldridge, the editor of Jane's Nuclear, Biological and Chemical Defence, Iraq, Russia and Iran are likely to have large quantities at their disposal.
Overall risk
One problem for health experts would be distinguishing a terrorist attack from a natural outbreak of food poisoning.
John Eldridge said: "Botulism toxin was considered by coalition forces to be a viable threat during the Gulf War. Some 10,335 kg was destroyed under UNSCOM [United Nations Special Commission] supervision."
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Smallpox
What is it?
Smallpox is a viral infection caused by the variola virus. One of the biggest killers in history, the disease was effectively wiped out in the 1970s by a worldwide vaccination plan.
Symptoms
The incubation period is about 12 days. First symptoms include fever, tiredness and an aching head and back. Over the next few days, a distinctive rash develops, usually on the face, legs and arms.
Lesions then appear, which form crusts and fall away within a few weeks. Death occurs in up to 30% of cases.
How is it spread?
Smallpox can be caught by inhaling the virus from an infected person. Sufferers are most infectious during the first week of illness.
In the event of a purposeful attack, the virus could be released in an aerosol, or suicide attackers could deliberately infect themselves. Its stability in air and high infection rate make the smallpox virus potentially very dangerous.
Is there an antidote?
There is a vaccine against smallpox but routine public inoculation ended in the 1970s as incidence of the disease declined. Everyone born before 1972 was vaccinated, but immunity has probably worn off by now.
In people exposed to smallpox, the vaccine can lessen the severity of, or even prevent, illness if given within four days of exposure. The US currently has an emergency supply of the vaccine.
There is no proven treatment for smallpox victims - except supportive therapy to combat the symptoms.
Availability
There are two World Health Organisation-approved repositories of variola virus - one at the US Center for Disease Control and the other in Novosibirsk, Russia.
The extent of secret stockpiles in other parts of the world remains unknown, but according to Jane's Defence, Iraq and Russia are likely to have the virus.
Overall risk
Smallpox is often cited as the most feared biological weapon. There is no proven treatment, and the virus could race through a population before anyone realises it has been released.
According to John Eldridge: "It is possible that cultures have found their way out of Russia and could be in the hands of terrorists."
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Plague
India had an outbreak of pneumonic plague in 1994
What is it?
Plague is an acute bacterial infection caused by Yersinia pestis. There are two main strains - bubonic and pneumonic.
Symptoms
In bubonic plague, the bacteria invade the body causing swollen lymph nodes and fever. The less frequent pneumonic plague causes severe respiratory problems, including coughing and breathing difficulties. The incubation period is usually between one and seven days.
How is it spread?
Bubonic plague is generally not spread from person to person, except through direct contact with fluids from the swellings. The disease is mainly transmitted from the bite of infected fleas carried by rodents.
But pneumonic plague can be passed on by face-to-face contact, through the inhalation of bacteria from a sneeze or cough of an infected person.
Terrorists would most likely attack by spraying an aerosol containing plague bacteria, causing the pneumonic variety.
Is there an antidote?
Plague can be effectively treated with antibiotics such as streptomycin and tetracycline. In treated cases, death occurs in fewer than 5% of victims, but if left untreated mortality rates can be higher than 90%. There is no vaccine.
Availability
Natural outbreaks of plague still occur - most notably in Africa, Asia and western USA. The bacterium responsible is also widely available in microbe banks around the world.
According to Jane's Defence, America, Iraq, Russia, Iran and possibly North Korea have supplies of the bacterium.
Overall risk
Pneumonic plague is less virulent than smallpox but more so than anthrax. John Eldridge said: "Plague is a possible low-tech choice as successful vectors include insects and rodents."
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Tularaemia
What is it?
Francisella tularensis, the organism that causes tularaemia, is one of the most infectious bacteria known.
Symptoms
Symptoms vary according to the method of infection. If the bacteria are inhaled, symptoms can be similar to pneumonia.
Victims who ingest the bacteria may get a sore throat, abdominal pain, diarrhoea and vomiting. Untreated, the disease could progress to respiratory failure, shock and eventually death. The overall mortality rate is about 5%.
How is it spread?
Tularaemia is not spread though human-to-human transmission. Many small mammals harbour the disease, and naturally-acquired human infection occurs through animal bites, ingestion of contaminated food or water and inhalation of infective aerosols.
Aerosol dispersal would be the most likely method of terrorist attack.
Is there an antidote?
There is an effective vaccine, and the disease is treatable with antibiotics.
Availability
During World War II, the potential of F. tularensis as a biological weapon was studied by both sides.
Tularaemia was one of the biological weapons stockpiled by the US military in the late 1960s, but the supply was subsequently destroyed.
The Soviet Union continued production into the early 1990s. Jane's Defence believe that Iraq and Russia are likely to have stockpiles of this bacterium.
Overall risk
Tularaemia is considered to be dangerous because of its extreme infectivity and because it is easily spread. But it would not kill the vast majority of those infected.
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Haemorrhagic fever
What is it?
Quarantine is used to prevent the spread of Ebola in Africa
What is it?
The most well-known haemorrhagic fever is Ebola, caused by a virus of the same name. A similar disease, also found in the tropics, is caused by the Marburg virus. Both are lethal and relatively easily transmitted.
Symptoms
Within a few weeks of exposure, ebola victims suffer from headaches and muscle aches. They may also experience nausea, chest pain and profuse bleeding. More than half of all Ebola sufferers die from the disease.
How is it spread?
The virus can spread from person to person, through direct contact with blood or other secretions.
Is there an antidote?
For both Ebola and Marburg, there is no cure, no vaccine and no treatment.
Availability
Like cholera and typhoid, these diseases are endemic in many poor countries. There is also speculation that the Soviets experimented with the Marburg virus for its use as a biological weapon.
Overall risk
Haemorrhagic fevers are unlikely to be an obvious choice as they are so hazardous to work with. But, said John Eldridge, perpetrators could quickly acquire the capability to use these germs as weapons. back to top