Example communicable diseases

Infects: Humans

Symptoms: Fever and a red skin rash. Can be fatal if complications arise.

Treatment/control: None, but most young children are vaccinated against measles.

Spread by: Inhalation of droplets from sneezes and coughs.

Infects: Humans

Symptoms: Initially causes flu-like symptoms (sneezing, coughing, fever). Unless successfully controlled the virus attacks the body’s immune cells. Late-stage HIV infection, or AIDS, occurs when the body's immune system becomes so badly damaged it can no longer deal with other infections or cancers. 

Treatment/control: Antiretroviral drugs are used to slow the reproduction of HIV, but there is no vaccine and no cure.

Spread by: Sexual contact or exchange of body fluids, such as blood, occurs when drug users share needles.

Infects: many plants, including tomatoes.

Symptoms: Gives a distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis.

Treatment/control: None, but some resistant crop varieties are available.

Spread by: Contact between diseased plant material and healthy plants.

Infects: Humans

Symptoms: Fever, abdominal cramps, vomiting and diarrhoea are caused by the bacteria and the toxins they secrete. 

Treatment/control: Plenty of fluids to prevent dehydration. In the UK, poultry are vaccinated against Salmonella to control the spread.

Spread by: Bacteria ingested in food, or on food prepared in unhygienic conditions

Infects: Humans

Symptoms: Thick yellow or green discharge from the vagina or penis and pain on urinating.

Treatment/control: Was easily treated with the antibiotic penicillin until many resistant strains appeared. Now treated with different antibiotics. Spread is controlled by the use of a barrier method of contraception such as a condom.

Spread by: Sexual contact.

Infects: Rose plants.

Symptoms: Purple or black spots develop on leaves, which often turn yellow and drop early. It affects the growth of the plant as photosynthesis is reduced. 

Treatment/control: Can be treated by using fungicides and/or removing and destroying the affected leaves.

Spread by: Wind or water.

Infects: Humans but has a lifecycle that includes the mosquito.

Symptoms: Recurrent episodes of fever that can be fatal. 

Treatment/control: The spread of malaria is controlled by preventing the vectors (mosquitos) from breeding, such as removing areas of still water and using insecticides. Mosquito nets are used to avoid being bitten.

Spread by: Mosquitos.