How long can bacteria live on a doorknob? © Getty Images

How long can bacteria live on a doorknob?

Ah choo! Germs are all around you and can survive longer than you would think.

Asked by: Max E Jones, USA

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On a hard, non-porous surface like a door handle, most viruses are destroyed within 24 hours.

The survival time for bacteria is more variable. Salmonella only lasts four hours, but MRSA can last several weeks and C. difficile has been found to survive for up to five months. On clothing or skin, the survival time is roughly halved. This may be because these surfaces dry out more quickly, or because they interfere with the bacteria’s ability to produce protective biofilms.

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