Theatre is contagious, writes PETER CRAWLEY

Long experience taught the critic James Agate that nobody goes to the theatre unless they first have bronchitis. Listening to the seasonal chorus of hacking coughs, snivelling harmonies and the gentle rustle of Kleenex and lozenge wrappers, it’s easy to mistake most theatres for convalescence homes.

Misery loves company, of course, which may be why people will still go to a show with frogs in throats. But company never seems that fond of misery. One of the reasons people will tut-tut at every mobile phone disturbance is because they can’t be quite so aggressive with somebody succumbing to consumption in row G. Instead, they release their frustrations at the first sign of an electronic scapegoat – which is why you should set your ringtone to the sound of a cough.

There's another reason that audiences have little collective sympathy for the afflicted. If you've come out to see La Ronde, for instance, or A Long Day's Journey into Night, or Angels in America, the last thing you want is to be distracted from those compassionate and brutal studies in communicable disease by a bunch of sick people.

Such is the strange contradiction in illness on and off the stage: the place you might go to collectively tease out society's ills or unravel the political metaphor of a plague is the same place you might catch something airborne. Can you properly appreciate the strident allusions to hereditary disease in Ibsen's Ghosts, for instance, if you're worried that the person next to you is in the early stages of swine flu?

We may worry periodically about various pestilences that will, at some point, annihilate our species, but the Black Death really didn’t mess around. Given that health care at the time amounted to little more than lancing, leeching and some prescriptions for liquorice, it’s fascinating that the images of sickness from Elizabethian-era stages are so luridly unsanitised.

Soldiers in Shakespeare's Henry IVcomplain about having a "whoreson cold, sir, a cough" which earns them short shrift ("thou shalt go to the wars in a gown"). Even filial communication in King Lear, sounds like deadly contagion: "Thou art a bile, a plague-sore, or embossed carbuncle, in my corrupted blood." The Bubonic Plague would see theatres shut down as incubators of deadly disease, so there's something brilliantly defiant about this poetry of pathogens, as though a dose of sickly metaphors might boost the audience's immune system, like an inoculation.

Are things so different now in an age of zealously guarded personal space and sensationalised epidemics? When Freefall, the Corn Exchange's current play in Project, whips us between hospital wards and the imaginative reaches of a suffering mind, it lays bare both the disease of a man and implicitly of a nation.

Maybe Agate’s observation requires a second opinion. Nobody goes to the theatre without a more subtle ailment, a shared unease for which there is no diagnosis or vaccine, but a real possibility of recovery. And they’ll keep going until somebody finds a cure.