viruses

• Viruses


  • Not cells, not living, but considered organisms
  • About 10,000 times smaller than animal cells
  • Can't reproduce by themselves, but can use a host cell's machinery to make copies of themselves
  • Can burst the host cell to release new viruses to infect other cells
• Viruses can damage the body and make people feel ill
• Viral diseases covered


  • Measles
  • HIV
  • Tobacco mosaic virus
• Measles virus


  • Spread by droplets when an infected person coughs or sneezes
  • Generally causes a red rash and fever
  • Can be serious and even fatal
  • Rare in UK due to vaccination
• HIV


  • Human Immunodeficiency Virus
  • Spreads through sexual contact or sharing bodily fluids
  • Initially causes flu-like symptoms
  • Gradually weakens the immune system
  • Can lead to AIDS if left untreated
  • Can be managed with antiretroviral drugs
• Tobacco mosaic virus (TMV)


  • Affects certain plant species like tobacco and tomato
  • Causes discoloured patches on leaves, reducing photosynthesis and plant growth
• Viruses are the leading cause of certain diseases