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• A disease causes health problems by affecting an organism's body, organs, tissue or cells.
• There are many different types of disease that exist in the world today.
• Diseases can be caught, develop over time or be inherited.

• Communicable diseases are those which are infectious. This means they can be transferred from one organism to another. An example of this is the common cold.

• Non-communicable diseases are not infectious. This means they cannot be transferred between one organism and another. An example of this is chronic lung disease. Genetic diseases are also considered to be non-communicable. An example of this is sickle cell anaemia.

Cancer is a non-infectious disease, therefore we say it is non-communicable. It is not caused by a pathogen. Some lifestyle factors are linked to cancer, such as eating a poor diet, being exposed to radiation and smoking. However, there are also cancers that do not have a specific known cause, and research is ongoing into what might cause them.

Cancer happens when the cells in a person's body grow out of control. This often leads to a tumour. Some tumours are benign, which means that they do not spread. Other tumours are malignant, which means that they spread to other parts of the body and cause other tumours to grow.

Treatments for cancer include surgery, radiation therapy and chemotherapy, which uses harsh drugs to try and kill the cancerous cells. There are also treatments that are still being trialled, such as immunotherapy.

Measles is a highly infectious viral illness that can sometimes lead to serious complications. It is therefore considered to be an example of a communicable disease.

Symptoms can include:

• cold-like symptoms, such as a runny nose, sneezing and a cough
• sore, red eyes
• a high temperature or fever
• small greyish-white spots on the inside of the cheeks

Measles can be unpleasant, but will usually pass in about seven to ten days without causing any further problems. However, in some cases measles can lead to serious and potentially life-threatening complications. These can include infections of the lungs and brain.

The measles virus is contained in the millions of tiny droplets that come out of the nose and mouth when an infected person coughs or sneezes. You can easily catch measles by breathing in these droplets or, if the droplets have settled on a surface, by touching the surface and then placing your hands near your nose or mouth. There is no specific treatment for measles. If you contract measles, you are advised to rest, take painkillers and drink plenty of fluids to help ease the symptoms until it has run its course. However, measles is now uncommon in the UK because of the effectiveness of vaccination.

Find out more about vaccines and antibiotics.