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Agents of Bioterrorism

By: Swasti Tyagi

Bioterrorism is deliberately using biological agents of warfare, which are usually microorganisms such as bacteria and viruses, to cause widespread harm to human populations, animals and crops (also known as agro-bioterrorism). Agro bioterrorism is carried out to cause economic harm. It is feared that large-scale biological warfare may result in severe damage and panic due to difficulties in the mitigation and prevention of the spread of diseases through microorganisms. The possibility of artificial genetic modifications makes it more convenient for anti-social elements to carry out attacks.

It is difficult to take immediate action when a disease is released intentionally since the occurrence of the attack is only indicated to respective authorities after symptoms would have already appeared in several members of a population, along with unfortunate fatalities as well. Rapid advances in research in genetic engineering and gene modification technology increase the risk of such attacks, especially in a scenario where the resources required for the same happen to fall into the wrong hands. It can lead to the creation and production of more resistant and lethal strains of microbes, which, if gone undetected, would be very difficult to manage and bring under control.

Due to the invisible and infectious nature of most of the agents used in bioterrorism, public health authorities and defence organisations need to stay on high alert to take action at even the slightest sign of a bioterrorist act.

The agents of bioterrorism are divided into three major categories by the CDC based on mortality rate, frequency of use and lethality, namely:

Category A: Includes anthrax (Bacillus anthracis), botulism (Clostridium botulinum toxin), smallpox (Variola major), and viral hemorrhagic fever - caused by filoviruses such as Ebola. These are the agents of the highest priority for authorities to keep a lookout for due to their highly infectious nature and high mortality rates. They can lead to a widespread impact on public health and can cause social disruption.

Category B: Includes food safety and contamination threats such as the Salmonella species and the ricin toxin from Ricinus communis (castor beans). They are second on the priority list of agents to look for. They are relatively easier to bring into control and have lower mortality rates compared to Category A agents.

Category C: Includes emerging infectious diseases such as Nipah virus and Mycobacterium tuberculosis. These agents have the potential to be genetically engineered to become efficient weapons of mass destruction, although they have not been used as bioterrorism agents to date.

Some newer agents that can be used and are worth looking out for are ‘designer substances’ such as cytokines, hormones and neurotransmitters. These are obtained as products of microbes and are also known as bioregulators. Compared to traditional weapons of bioterrorism, which can take anywhere between a few hours to even a few days to show any effect, these have the potential to take action within a brief period after administration.

Agro-bioterrorism can be carried out by affecting the processes carried out while transferring agricultural products from the farm to the consumer and infecting livestock and crops. Contamination and initiation of outbreaks are carried out during the processing, manufacturing, storage, transporting or distributing of processed food products. Parasite-based biological weapons are believed to be under trial to affect cash crops.

Let’s take a deep dive into some of the most popular and well-known bioterrorism agents from each category, considering their lethality, mode of transmission, previous use and potential as bioterrorism agents.


It is caused due to the organism Bacillus anthracis, a gram-positive, rod-shaped bacteria. It is spread to humans either by coming in contact with infected animals or their products or by direct exposure to spores.

A unique feature of this particular agent is its spores. These spores can be formed effortlessly in a dry form. They are also colourless, odourless and tasteless, making them invisible to physical detection. The spores remain in nature for an extended period after formation, either in the air in the form of powder or it resides within the soil. All these features make it an excellent bioweapon, and it has been used in the past on a small scale.

On exposure to the agent three types of symptoms of anthrax can be observed within seven days of exposure to it:

Skin/Cutaneous: Blister formation, with a gradual progression into a skin ulcer with a black area in its centre, is observed

Inhalation: Symptoms are similar to that of a cold and flu. It starts with a sore throat and muscle aches and later progresses to chest pain, cough and shortness of breath. It can eventually lead to a more severe form of meningitis, shock and even death.

Gastrointestinal: A sense of nausea, loss of appetite and bloody diarrhoea is followed by a fever and terrible stomach pain.

There are no current vaccinations for anthrax; therefore, it can only be treated for individuals who have only recently acquired the disease without displaying severe symptoms. It is treated using the antibiotics doxycycline, penicillin or ciprofloxacin.

Contamination of food products through members of the Salmonella spp. :

This genus is part of the family Enterobacteriaceae. It consists of rod-shaped, Gram-negative anaerobic bacteria.

There are two existing serotypes; typhoidal and non-typhoidal. The typhoidal type directly infects humans inducing the infamous Typhoid fever, while the non-typhoidal type indirectly spreads through contaminated and infected livestock. It is, therefore, quite easy to contaminate food products and water sources on a large scale using this bacterium. It is essential to perform regular food and water safety checks to prevent an attack of this nature and for us to regularly wash and heat vegetables, fruits, poultry and dairy products before using them for cooking.

Symptoms of typhoid in the gastrointestinal system usually start showing up within 4 to 72 hours of ingesting contaminated food and water and last for about a week before the microbe itself is excreted and thrown out of the body via faeces. The symptoms include nausea, vomiting, fever and chills, and diarrhoea.

Typhoid infections don’t commonly cause fatalities and can be treated simply through rehydration and antibiotics, thus classifying Salmonellae as a Category B agent. However, infants, elderly and immuno-compromised patients are at high risk of developing fatal meningitis upon contracting any strain of Salmonella; they have to take extra precautions. Due to the ease of availability and method of contamination, it is still an agent for public health agencies to look out for.

Nipah virus:

It is a zoonotic virus that belongs to the family Paramyxoviridae. While it has only caused a few recorded outbreaks, its high mortality rates are of great concern. This qualifies it to fall under Category C, because it can be highly lethal and fatal if obtained and utilised as an agent of bioterrorism.

Studies have found that it has been commonly transmitted from infected pigs to humans through direct contact with contaminated tissues or body fluids. It is not known whether the infection can be transmitted between humans. It is believed that fruit bats might act as natural hosts for this virus, which may sound familiar - if you know, you know.

The worst part is there is nearly no hard and fast cure for infections caused by this virus. While initial symptoms may resemble those of influenza, what follows is much more fatal and dismal - the infected person feels disoriented and goes through physical convulsions before finally settling into a coma. This syndrome is known as acute Nipah encephalitis. The only possible cure for this syndrome is treatment with the antiviral drug ribavirin, which may - or may not - reduce the mortality rate, as per the given evidence.

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