3.1.2 Viral Diseases

• Are viruses living organisms?

  No.
• Are viruses made of cells?

  No.
• How many times smaller are viruses than animal or plant cells?


  10000.
• How do viruses spread and multiply?

  1. Viruses can spread between humans via the air, contaminated food or water, or by direct contact.
  2. As they can't reproduce themselves, viruses have to enter one of our cells, and then use it to create multiple copies of the virus itself.
  3. Once there are lots of copies, the viruses cause the cell to burst, and then go on to infect neighbouring cells.
• How can measles be spread between people?

  Through respiratory droplets when an infected person coughs or sneezes.
• What are the two main symptoms of measles?

  Fever and a red skin rash.
• Are most people vaccinated against measles?

  Yes.
• Why are most people vaccinated against measles?

  It is a serious illness that can be fatal if complications arise.
• What does HIV stand for?

  Human Immunodeficiency Virus.
• What does immunodeficiency mean?

  A weakened immune system.
• Which two ways can HIV be spread between people?

  Sexual contact and exchange of bodily fluids.
• Infection from HIV can lead to…?

  AIDS.
• What is AIDS?

  Where the immune system is so weak that a person can very easily catch unusual infections.
• What does AIDS stand for?

  Acquired Immunodeficiency Syndrome.
• What is the treatment for HIV/AIDS?

  Antiretroviral drugs.
• What does HIV initially cause?

  A flu-like illness.
• What type of organism does Tobacco Mosaic Virus (TMV) infect?

  Plants.
• What two plants does Tobacco Mosaic Virus mainly affect?

  Tomato and tobacco plants.
• What is the main symptom of Tobacco Mosaic Virus (TMV)?

  Patches of the leaves get discoloured.
• Tobacco Mosaic Virus (TMV) reduces the amount of photosynthesis that a plant can do. What are the consequences of this?


  The plant won't be able to produce as many sugars and will not grow as well.