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Infectious diseases - pathogens

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Viruses are very tiny – they are much smaller than bacteria or fungi . They measure only a few thousand millionths of a metre (nanometres).

All natural viruses cause disease including the common cold, influenza (flu), measles, mumps and rubella. They are not living cells themselves, and they can only reproduce inside other living cells.

Viruses can attack all different types of living organisms – they invade animal, plant and even bacterial cells. Different viruses attack specific cells – so the 'flu virus attacks the cells of the respiratory system while the virus which causes meningitis attacks the cells of the membranes which cover your brain.

Scientists have started to use viruses to benefit people. They are an important tool in genetic engineering. They are used to carry new genes into the DNA of the cells of other organisms.

In the disease resource, you can find out more about flu, chickenpox and HIV/AIDS, all viral diseases.

Hiv Mature Scale
Hiv Parts

The structure of viruses

  • Glycoproteins
    Protein spikes embedded in the virus envelope. This attaches to and penetrates the host cell
  • Envelope
    Outer surface of the virus
  • Capsid
    core that contains the genetic material and enzymes of the virus
    Viral genetic material that codes for the viral enzymes
  • Enzymes
    Proteins necessary to replicate the virus and infect the hosts