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Asked by Maddie to Aaron, Abbey, Keith, Natalie on 18 Nov 2015. This question was also asked by ellie loves pizza.
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Natalie Garrett answered on 18 Nov 2015:
Ok to answer the examples you’ve given, cancer and HIV are caused by very different things. HIV is caused by a virus, and is usually transmitted by direct contact between one person’s blood and an infected person’s blood. Cancer, on the other hand, is not contagious for humans. Cancer is caused by a combination of things, including your genetic predisposition, your lifestyle and exposure to carcinogenic (cancer-causing) chemicals.
In terms of testing for these and other diseases, you have to screen people. Each disease will have different signatures that you can look for in blood or other samples. Sometimes you have to take pictures of the inside of a person, using x-rays or MRI imaging.
For the HIV infection, you have to be tested twice before you know for sure you don’t have it after being exposed to something that could have infected you, with a few months between the two tests. This is because the virus replicates slowly, so it’s possible that even with a test result that shows no HIV to begin with, you may actually have had a small number of viruses (too small to detect) that you then can only detect for sure once they’ve multiplied enough by the time the second test comes around.
Cancer can take a while to test, and this is mostly because of the strain on the healthcare system. If the government put more money into the NHS, waiting times would most likely be shorter. Doctors have to decide who needs treatment and testing most urgently, but there are limits on what they can do with the resources available to them. If you want to improve this, when you’re old enough to vote, vote for a party that won’t cut resources to the NHS!
In terms of finding out what actually causes the disease in the first place, this can take a while because you have to test a lot of theories before you know for sure which one is correct. Scientific testing needs to be rigorous otherwise you can’t trust your results, and this takes time.
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Aaron Boardley answered on 18 Nov 2015:
The very question you have asked is part of the answer.
Before finding out what causes medical conditions, scientists ask the same question you have – they ask themselves ‘how can we find this out?’. The long process comes, in part, by trying to design reliable tests, but when something is new it is hard to know what you’re looking for. You have to look at lots of evidence, lots of examples, compare healthy people and sick people, look back through medical histories. You have to work out whether it was caused by a virus (like HIV), or genetics, or things in the environment – like poison or bacteria.
Ruling out some options might be quick, but others might take longer. Once you’ve ruled some things out, and you have an idea of what sort of problem you’re looking at (e.g. you know it is probably due to a virus) – you then have to try and find what that virus looks like. This means you need sick people, or samples you’ve kept from previously sick people, to test and look at – but have to be aware that some things (like bacteria) can evolve over time, so the thing that cause a certain disease might keep changing the same.
The more scientists you can get researching something like this, and the more money they’re provided with for time and equipment, then the quicker it can happen. It’s also important that scientists share their results – these days it’s far quicker to share information than it was in pre-internet days. This means scientists in different countries can make use of one another’s work to make advances even quicker, but as always it still needs more time and money.
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