3.1.2 Viral Diseases

What are viral diseases?

Viral diseases are caused by viruses that can enter all types of cells. They are difficult to treat as there are no medicines that can cure them.

What are the symptoms of measles?

Fever and red skin rash, which can lead to pneumonia, encephalitis (brain infection), and blindness.

How is measles spread?

By droplet infection.

How is measles prevented?

By vaccinating young children to reduce transmission.

What are the symptoms of HIV?

Initially flu-like symptoms. Later, the virus attacks the immune system and leads to AIDS, a condition where the body is vulnerable to many other diseases.

How is HIV spread?

By sexual contact or exchange of bodily fluids such as blood.

How is HIV prevented?

Preventing spread (e.g. using condoms, not sharing needles, screening blood, HIV+ mothers bottle-feeding instead of breastfeeding) and preventing development into AIDS with antiretroviral drugs.

What are the symptoms of Tobacco Mosaic Virus (TMV)?

Discolouration of the leaves, so affected parts cannot photosynthesise, reducing yield.

How is TMV spread?

By contact between diseased plants and healthy plants, or via insects acting as vectors.

How is TMV prevented?

Good field hygiene, pest control, and growing TMV-resistant strains.