• Question: How are diseases "made"?

    Asked by anon-244767 on 29 Apr 2020. This question was also asked by anon-256870, anon-257533, anon-257812.
    • Photo: Alena Pance

      Alena Pance answered on 29 Apr 2020:

      That depends very much of the type of disease. So there are diseases caused by external factors, like parasites that invade our bodies leading to all sorts of problems or contaminants, poisons, present in the environment that surounds us that change the function of our cells. And other diseases are caused by changes in our DNA that either result in malfunctioning proteins or no protein at all. These are usually inherited from our parents because the genetic changes are in the DNA and are therefore transmitted to us with the DNA of our parents. Environmental factors can also result in changes in the DNA that will be responsible for disease. For example it has been shown that smoking cigarettes causes genetic changes in the lungs and some of these changes can lead to lung cancer.

    • Photo: Sophie Pritchard

      Sophie Pritchard answered on 30 Apr 2020:

      This is an excellent question! There is a selective pressure for bacteria and virus’ to evolve and adapt, so that they can enter our bodies and go undetected by our immune system. Bacteria and virus’ are therefore always mutating (changing their genetic makeup). Some of these mutations give them an advantage. If our bodies haven’t seen these bacteria/virus’ before then it takes time for us to build up the B cells (memory immune cells) and T cells (attacking immune cells) of our immune system. This gives the bacteria and/or virus enough time to infect our tissues and cause symptoms which make us ill. This is why people need to have a new flu jab every year, because the virus has mutated and the previous injection would no longer be effective. The new flu virus isn’t necessarily a new illness, but it is a different strain. I hope that helps to answer your question 🙂

    • Photo: Alex Holmes

      Alex Holmes answered on 30 Apr 2020:

      This is a fantastic question, because it’s actually one scientists and doctors are asking ALL the time! So it’s really impressive you’re having the same thoughts!

      If we know how a certain disease is made, it means we can start to work out how to “fix” the disease. For example, if something went wrong in a car you might go to a mechanic and they would say “ah yes it’s a problem with the brake fluid or there’s a leak in this pipe or the tyre is punctured”. So the mechanic has worked out where the issue is coming from and how to fix the cause – whether that’s adding more brake fluid or patching up a leak or changing a tyre. It’s just the same with diseases, a doctor might say “ah yes it’s a problem with the DNA or there’s a germ or there’s a problem in the kidney” and then know how to fix or help with this.

      There’s plenty of different types of diseases, some are to do with DNA, some to do with germs or bacteria, some to do with certain organs, some to do with lifestyle and some to do with environment. Some of these we understand really well, like infections are caused by bacteria and viruses, so we can give an antibiotic or antiviral to stop the bacteria or virus from working and therefore stop the infection. Or for genetic diseases, we know it’s caused by a certain gene or piece of DNA going wrong so we can try to minimise the effect of that or try gene therapies. Or if there’s a problem in the heart which makes it beat weirdly, we can add a pacemaker to make it beat normally.

      However, there’s diseases we’re still trying to work out how they’re made because there’s no clear answer. For example, certain mental illnesses like depression are really hard to understand because the symptoms (or signs of disease) are different in different people, or there’s no clear way of working out if a particular brain pathway or process isn’t working the way we would expect. Also, it’s normal and healthy to feel sad and depressed sometimes, so how do we tell the difference?

      So overall diseases are usually caused by something in the body going “wrong” like an organ or DNA, or by an outside source like bacteria. And understanding how things have gone wrong is key to helping them get right again.

    • Photo: Helena Fisk

      Helena Fisk answered on 30 Apr 2020:

      This is a great question and just to build on the two fantastic answers below I thought I would add an answer about how metabolic/inflammatory diseases that we are not born with can occur. Diseases such as type two diabetes, non-alcoholic fatty liver disease, and atherosclerosis (fat in our arteries) as often associated with obesity. Obesity develops when an individual has an above normal/healthy amount of body fat which can occur due to a mix of factors such as our genetics, taking medications, and our lifestyle (consuming too much high fat and energy food, and not exercising regularly). As obesity develops, our bodies respond by releasing chemical signals that try to help us adapt and store excess fat. Our bodies are usually pretty good at balancing these chemical signals to keep the normal functions in our bodies running smoothly (we call this homeostasis). However, in obesity, this balance is lost and we see an increase in inflammation. This can result in disruption of normal functions such as responding to insulin which is released when glucose is sensed in the blood after eating a meal. This is called insulin resistance and is a feature of type-2 diabetes. This can also affect the normal storage of fat in our bodies resulting in it accumulating where we do no want store fat such as in our arteries and our liver. The changes in our body as we gain weight occur slowly and disease worsens over a long period time. This is described as being chronic. Other diseases such as those caused by viruses and bacteria described by Sophie below, develop quickly and cause us to feel ill quickly (for example you may feel ill within a couple of days after catching the flu). These are described as acute diseases and often require urgent and short term treatment or go away on their own as our bodies immune system manages to fight them off (e.g. the common cold). I hope that helps 🙂

    • Photo: Laura Durrant

      Laura Durrant answered on 30 Apr 2020:

      That is a big question – and an excellent one! There are lots of different types of diseases that can come about in different ways. However, one thing that is common between most (if not all of them) is that our genetic make up effects what type of diseases we can get and how bad they can be to our health.

      For example, some diseases can be passed down families as a result of a faulty gene. These are called ‘inherited’ diseases. Genes are important for regular bodily function – so when there is a mistake in a gene (like a mutation) this could impair the function of that gene and result with an associated disease. Common examples are Alzheimer’s and Parkinson’s disease, as well as cancer.

      Although, a person can be born without these errors in their genes, but could still develop a disease. Genetic mutations can happen as a result of how healthy we are (like if we smoke, what we eat and how much we exercise) as well as our environment (like pollution and UV light from the sun). This is why it is recommended that we live as healthily as we can!

      Our genes can also affect the way we become infected by microbes, like bacteria, parasites and viruses. Some genes encode receptors on the surface of our body cells – it is these receptors that microbes use to enter the body and infect. Some people have lots of these receptors, while some people don’t. Those with more receptors are more likely to get ill.

      General health and age also affects microbial infections; a healthy diet can boost the immune system and protect against microbial infection. Meanwhile, older people generally have weaker immune systems, which means they are more likely to become ill compared to younger people.

      I hope that answers your question! 🙂

    • Photo: Nicole Wheeler

      Nicole Wheeler answered on 30 Apr 2020:

      Awesome question, and one I spend a lot of my research time looking at! I research how bacteria go from being relatively harmless to humans to being really dangerous. One of the most interesting things about studying this is that bacteria developing the ability to cause disease can be thought of as an “accident”. Bacteria don’t make decisions about what to do or how their DNA will change in the future. They just respond to their environment with the DNA they have and the genes that it encodes.

      Since we developed the ability to read the DNA of bacteria, we found out that a lot of the really dangerous bugs actually carry around a lot of broken DNA. This is because when they infect a host, like us, they can use the host for food and shelter, meaning some of the genes they used to need aren’t needed any more.

      Bacteria are mutating all the time, and if the mutation isn’t harmful, they carry on growing and spreading. There are lots of ways mutations can break a gene, but only a few ways they can fix a broken gene, meaning genes are slowly being broken down if they’re not needed. Once bacteria have lost genes they need to survive outside their host, they’re then a bit stuck, and the only way to survive and thrive is to get really good at growing in that host. Sometimes that means growing harmlessly or even helping us, like the bacteria that live in our gut, but sometimes it means causing us harm to get access to more food and stop the immune system from killing them.

    • Photo: Ben Wiggins

      Ben Wiggins answered on 1 May 2020:

      A very good question! There are lots of ways a disease can develop, and I like to first split different diseases into broad categories. Infectious diseases happen when certain viruses or bacteria get into our bodies and start attacking our own cells (not all bacteria though as lots of them are ‘good bacteria’ that live inside us and help us by making vitamins we need, or educating our immune systems in exchange for a nice place to live. In fact some scientists think each one of us contains 10 times as many bacteria as human cells! But I am getting sidetracked..). Other diseases like cancer happen when our own cells lose control over themselves because of a build up of mutations (changes in the structure of our genes) and start dividing, and then we have diseases caused accidentally by our own immune systems – like autoimmune disease when the immune system attacks our own cells by mistake, or allergy where immune cells overreact to something harmless like tree pollen or house-dust mites that live in our carpets. We also have genetic diseases like cystic fibrosis where because of a certain mutation in the lung cells, it’s harder to clear mucus. These type of diseases are ‘inheritable’ because a copy of the faulty gene mutation can be passed on to the children of the patient. There are many more examples, like obesity which is mostly caused by bad diet and lack of exercise, and some diseases we still have a lot to learn about like depression and anxiety.

      There are lots of different ways to classify these diseases, you could do it by the organs they affect, whether they affect the body or the mind, by whether they are infectious or not and loads more! What I find fascinating is that for most of these diseases develop due to a combination of the environment (diet, exercise, smoking, contact with infectious bacteria/viruses), and your genes. To try and unravel the contribution of any one thing is very complicated, but that’s why we need scientists interested in all different areas of disease to work together to get a better understanding of the whole process. We are understanding human disease more and more every day and it’s exciting to play a part, even if a very small one, of helping to make better treatments for disease in the future!

    • Photo: Valerie Vancollie

      Valerie Vancollie answered on 23 Jun 2020:

      An excellent question, unfortunately there is no one simple answer. The things we classify as ‘disease’ encompass a lot of different things.
      Some are simple accidents. A lot of diseases with a genetic component could fall into this category. We often think of genes as destiny, but this isn’t the case and they can be affected by a lot of different things like smoking, UV, chemicals and even the diet we eat or the exercise we take. Those things can effect whether genes are turned on or off or they could induce changes (mutations) that can be quite harmful and lead to cancers…
      Some are adaptions gone wrong like how we evolved to crave foods high in fat or sugar as that might have saved our ancesters’ lives back when food was scarce and you never knew when your next meal was coming. Now, of course, it can lead to obesity and all of the related diseased. Sickle cell anemia is another interesting one, if you have 2 bad copies of the gene in question you get very ill, but if you have only 1 bad copy you might be protected from malaria.
      Some, meanwhile, are a competition between different living organisms. Bacteria being a very big one here, but there are others like parasites, fungi… and then it becomes an evolutionary fight. Who can adapt better to survive? And our competition can often have a very big advantage as bacteria can reproduce in under half an hour, so they can evolve very quickly indeed compared to us!
      Another category is diseases we come across that evolved in other species and weren’t so bad in them. They only became really bad when we crossed paths with them. Ones in this category are HIV, flu, ebola, leprosy, West Nile virus…

Comments