3.1.2: Viral diseases
Not started yet — this one needs some love.
Measles: fever + red skin rash; spread by droplet inhalation (coughs/sneezes); can be fatal if complications arise; most children vaccinated.
HIV:
Initially causes flu-like illness.
Attacks immune cells (white blood cells/T cells).
AIDS = late-stage HIV; immune system so damaged it cannot fight other infections or cancers.
Spread by: sexual contact or exchange of body fluids (e.g. blood — shared needles for drug use; needle-stick injuries).
Controlled with antiretroviral drugs (do not cure but prevent progression to AIDS).
Tobacco mosaic virus (TMV):
Infects many plant species including tomatoes.
Causes mosaic pattern of discolouration on leaves.
Reduces photosynthesis → affects plant growth.
Spread by contact with infected plants.
Common exam mistakes
HIV is NOT spread by droplets or air — it is spread by sexual contact or exchange of body fluids. Measles IS spread by droplets.
HIV ≠ AIDS: HIV is the virus; AIDS is the late-stage condition when the immune system is severely compromised.
TMV affects plants (not animals); do not say it spreads through air or water like a human respiratory virus.
HIV: sharing needles (for drug use) is a key transmission route — do not omit this.