TETANUS

If approached by someone with a penetrating wound, no history of vaccination and a mocking grin your best course may be to call 000. That wry smile is actually a classic symptom of tetanus, a disease caused by a bacterium whose spores are ubiquitous in soil. Clostridium tetani releases a toxin that blocks the inhibitory neurotransmitter GABA, sending muscles into spasms of such violence they can break bones, shut down breathing muscles and, yes, contort the face into that involuntary smirk. Which all serves to make the exceedingly safe and effective option of vaccination even more appealing.