BARNARDO: Who's there? FRANCISCO: Nay, answer me. Stand and unfold yourself.

From the very opening moment of Hamlet, we get the impression that this world is indeed out of kilter. In the dim light, we see a person approach a sentry on his watch., but it is the visitor who challenges the sentry to identify himself, rather than the reverse. Error already appears to have taken hold. A good part of the exposition of the play informs us just how deep the illness of this world is. Metaphors of cancers, ulcers, poisons, infections, contagion, and putrefaction are commonly employed to depict Claudius' Denmark.

The action of Hamlet takes us into a royal household, a court and a country, all stricken with a mortal sickness. Claudius has committed murder in order to get to the throne. More, his murder has been that of a brother and has been followed by marriage to that brother's wife. The bond of kinship as well as the political bond has been dragged asunder. Claudius is tainted with the unnaturalness of Goneril and Regan as well as the blood-spilling ambition of Macbeth. From this central ulcer, the infection spreads outwards. Every relationship, every enterprise is touched with disease. Finally the illness is cured by the violent surgery of the last act. But only at the cost of Hamlet's own life among others.  - John Wain, The Living World of Shakespeare, St. Martins Press, N.Y. 1964. p.149.

The progress of the poison through the body of Hamlet's father mirrors the metaphorical poisoning of the body politic of the Danish court.

And in the porches of mine ears did pour The leperous distillment, whose effect Holds such an enmity with blood of man That swift as quicksilver it courses through The natural gates and alleys of the body, And with a sudden vigor it doth posset And curd, like eager droppings into milk, The thin and wholesome blood. So did it mine; And a most instant tetter barked about, Most lazarlike, with vile and loathsome crust, All my smooth body.  (I.v.63-73)

These images have had a certain resonance with post World War II American society, and have been commonly borrowed for use in American popular culture. In his film JFK, for example, Oliver Stone draws a parallel between post-Kennedy America and Hamlet's Denmark. This parallel is based on the notion, earlier seen in Oedipus Rex, that a people will continue to suffer the effects of a murder until that pollution is removed by satisfactorily dealing with the murderer. Here's how Stone establishes the parallel:

We've all become Hamlets in our own country, children of a slain father-leader whose killers still possess the throne. The ghost of John F. Kennedy confronts us with the secret murder at the heart of the American dream.