I watched this film again last night. I've seen it several times before, and I love it more each time I see it.
The way I see it, the virus itself serves only as a catalyst for the real plot. The film is actually about what would happen (on a personal level) if all of the social structures in which we live our lives ceased to exist. Selena and Mark represent the struggle simply to "exist", and have resigned themselves that this is as good as it gets (and attempted to become emotionless as a coping strategy). The father and daughter in the block of flats almost seem to be trying to maintain a sense of normality despite what has happened. And the military represent a regression to animal instincts (to defend and to reproduce). The main character Jim is not IMO a hugely important one until the end of the film where he also regresses to the point where Selina thinks he is infected. Is this suggesting that the non-infected are capable of the same acts of violence as the infected? Maybe the infection is not so important. The scientist at the beginning said in the laboratory that the disease is in the blood. But whose blood? The blood of the infected individual, or the 'blood' of society?
Maybe I'm over-analysing. But after several watches of this film it feels to me like a profound warning.
Any thoughts? :-)
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moto