Case studies of common communicable diseases
Infection and response • Communicable diseases
Flashcards
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Key concepts
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Measles (viral)
Measles is a viral infection that produces fever and a characteristic red skin rash. Transmission occurs by inhalation of tiny droplets expelled when an infected person breathes, coughs or sneezes, making the disease highly infectious. Infection of respiratory tissues and subsequent immune response cause the fever and rash observed.
HIV (viral)
Human immunodeficiency virus (HIV) is a virus that causes a flu-like illness in the early stage and progressively attacks the body’s immune cells, particularly helper T lymphocytes. Transmission occurs mainly via sexual contact or exchange of body fluids. Damage to immune cells reduces the body’s ability to fight other infections.
Salmonella (bacterial)
Salmonella bacteria cause food poisoning after ingestion of contaminated food. Typical symptoms include fever, abdominal cramps, vomiting and diarrhoea. Bacterial growth and toxin production in the gut cause inflammation of the intestinal lining, producing the listed symptoms. Transmission normally occurs when infected food is eaten.
Gonorrhoea (bacterial STD)
Gonorrhoea is a sexually transmitted disease caused by a bacterium. Typical symptoms in infected people include a discharge and pain on urinating. Direct sexual contact transmits the bacterium from one person to another. Localised infection of the reproductive tract produces the characteristic discharge and pain.
Malaria (protist)
Malaria is caused by protists of the Plasmodium genus and involves a life cycle that includes mosquitoes as vectors. Infected mosquitoes inject protist cells into the bloodstream when they feed. The protists invade and destroy red blood cells, producing recurrent episodes of fever as the parasite lifecycle repeats.
Tobacco mosaic virus (plant virus)
Tobacco mosaic virus (TMV) infects many plants and produces a mosaic pattern of discolouration on leaves. The damaged leaf tissue has reduced photosynthetic capacity, limiting the plant’s ability to produce glucose and reducing growth. The virus can survive outside a host under favourable temperatures and spread via contact or contaminated soil.
Rose black spot (fungal)
Rose black spot is a fungal disease that causes purple or black spots on leaves. Spread occurs by water or wind moving fungal spores between plants. Extensive leaf damage reduces photosynthesis, causing stunted growth and premature leaf drop; infected material is removed or treated to reduce spread.
Key notes
Important points to keep in mind