5.4 Viral Diseases Flashcards
What do viruses do?
- can infect and damage all types of cells
- replicate inside cells
- burst open the cells
Have scientists developed medicines to cure viral diseases?
No, so it is important to stop them spreading
Measles symptoms
- fever
- red skin rash
- red sore eyes
- can cause blindness and brain damage and may be fatal if complications arise
How do viruses cause damage?
Viruses are smaller than bacteria and have a regular shape, taking over cells and live and reproduce in cells, damaging and destroying them
ways to reduce spread of measles
- MMR vaccine
- infected people need to be isolated
treatment for measles
nothing
ways HIV is spread
- Direct sexual contact
- exchange of bodily fluids such as blood.
- Sharing needles, unscreened blood used for transfusions
- Can be passed from mother to child in breast milk
Ways to reduce spread of HIV/AIDs
- condoms
- not sharing needles
- screening blood used for transfusions
- bottle-feeding
symptoms of HIV/AIDS
- mild flu
- HIV attacks cells and after initial mild illness it remains hidden inside the immune system
- until the immune system is so badly damaged that can no longer deal with infections or certain cancers
- at this point the patient has developed AIDS
treatment for HIV
- no cure
- regular use of antiretroviral drugs can can prevent development of AIDS for many years
- this gives HIV positive people an almost normal life expectancy
ways tobacco mosaic virus is spread
- contact between diseased plant material and healthy plants
- Insects act as vectors
ways to reduce spread of tobacco mosaic virus
- good field hygiene
- good pest control
- remove all decaying leaves from plant and burn them
Symptoms of tobacco mosaic virus
discoloration on the leaves, small patches of light green, brown or yellow
treatment for tobacco mosaic virus
no treatment
TMV - resistant strains of many crop plants
Explain why the introduction of a vaccine decreases the number of cases of a disease
Immunisiation will prevent individuals from catching the disease. Therefore by a fewer carries of disease, less likely to spread to non-immunised indiviuals
How does a vaccine work
stimulates immune system to recognise and fight specific pathogen without causing disease itself
How do measles spread?
Air borne: spread by the inhalation of droplets from coughs and sneezes and is very infectious
Why has the number of people infected by measles decreased?
Vaccination means that people are immune to the disease, and so less people catch it
TMV destroys chloroplasts if the leaf. Explain how this could affect the growth of the plant.
- less chlorophyll present
- so less light is absorbed
- so reduced photosynthesis
