Tetanus is an infectious disease caused by a soil-borne bacteria called Clostridium tetani. Patients are often infected soil entering the blood through deep wounds, such as a cut. The bacteria produces a toxin called tetanospasmin which leads to the characteristic symptoms of tetanus involving muscle.

The term tetanus actually refers to a state where skeletal muscle remains contracted and cannot relax due to maximum signalling from the nervous system. Tetanus is associated with some distinct symptoms involving tetanised muscles.

Tetanus starts in the face in the form of lockjaw (jaw clamps shut and cannot be opened) and sardonic risus sardonicus. Risus sardonicus, also known as sardonic grin, is a contorted, malicious-looking smile that is caused by spasms of muscles in the face. A good portrayal of the grin is seen in the Joker’s face from the Batman comic book series.
The disease then progresses to cause stiff neck, spasming of chest and leg muscles and difficulty swallowing. 

A dramatic symptom is opisthotonos, where the patient experiences extremely painful contractions of back muscles causing them to arch their back against their will. Along with lockjaw and risus sardonicus, it is a characteristic sign of tetanus and has been known for centuries. Before it was attributed to tetanus, people used to think the person was possessed by a demon due to the agonised screams and involuntary spasming of the body.

The disease is especially devastating in infants and can be spread to the fetus within the womb. This is because babies do not have a developed passive immune system that can combat the infection. Neonatal tetanus carries a mortality rate of over 90% and is responsible for 15% of all neonatal deaths.

Tetanus is a preventable disease through immunisation. Immunisation is done by injecting an inactive form of the toxin (i.e. cannot cause disease), inducing a reaction by the immune system. This essentially “teaches” the immune system to defend the body against tetanus. By completing a course of three doses and receiving occasional booster shots throughout life, tetanus can be prevented. Pregnant women must be immunised against tetanus to prevent neonatal tetanus (the babies receive scheduled immunisations soon after birth too).

This is one example of how immunisation can effectively prevent fatal diseases in a population.

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