• Question: why isn't cancer contageous?

    Asked by hdlxhj to Tim, Sarah on 13 Jun 2011.
    • Photo: Tim Millar

      Tim Millar answered on 13 Jun 2011:

      This is a tricky one. Normally for something to be contageous it has to pass between two people like a cold or bacteria. Cancer cells would have to be passed between two people somehow and then set up home in the newly “infected” person. Most of us have an immune system which looks out for foreign invaders and removes them so would make passing cancer cells between two people very difficult.

      But… some cancers are caused by viruses (Burkitts lymphoma, Human papiloma virus and cervical cancer) which is not the same thing as a cancer being contageous but it is caused by an infecting agent.

      The other case is during transplantation of organs from one person to another. If the donor had an undetected kidney cancer for example this may continue to grow inside the person who received the new kidney. This is made even worse because during transplants, we use drugs to remove the immune system so our own bodies defence system is lost which makes it even harder to detect and remove cancer. Fortunately this is rare even in transplantation, bvut it is a known risk.

    • Photo: Sarah Thomas

      Sarah Thomas answered on 13 Jun 2011:

      Ok so things that are said to be contagious are diseases that can be passed from person to person. These are always diseases that are caused by an infection (like bacteria or a virus). The infection can be passed on by bodily contact, not washing hands, and if it is an airborne pathogen, then just being in the same room as someone can make you sick. Examples of airborne pathogens are meningitis, flu and pneumonia.

      The reason that cancer isn’t contagious is because it is not an infection. It is a disease where something goes fundamentally wrong with your body. Like heart disease – heart disease isn’t contagious either.

      The fundamental cause of cancer is damaged or faulty genes – the instructions that tell our cells what to do. Genes are encoded within DNA, so anything that damages DNA can increase the risk of cancer. When a new cells grows with this faulty DNA, it just doesn’t look right and then is grows and spreads really fast, and quickly forms a big lump of faulty cells called a tumour.

      Things that damage your DNA are things like smoking, drinking alcohol, eating unhealthy foods, and sun tanning.

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