 If you have a list of diseases with you, just like this, then how will you tell which ones are infectious and which ones are non-infectious? To answer that, you will need to know what are infectious and non-infectious diseases. Infectious diseases are the ones that spread from one person to another. Meanwhile, non-infectious diseases are the ones that don't. But why is that? Why do some diseases spread while the others don't? Well, infectious diseases are caused by pathogens like bacteria and viruses. They enter your body and multiply like crazy. And then they infect others via different excretions like a sneeze or cough or even feces. Non-infectious diseases aren't caused by pathogens at all. Since they don't rely on these disease-transferring agents, they stay limited to you. But they are still diseases that do a lot of damage to you. Instead of pathogens, non-infectious diseases are caused by genetic and environmental factors. Like being exposed to dangerous chemicals or leading a very unhealthy lifestyle or being born with a defective set of genes. However, you can prevent acquiring most of these diseases if you lead a healthy lifestyle. Now, there are some risk factors like age, gender and genes that you can't avoid. For example, you become susceptible to diseases when you're old. Some cancers are gender specific and diseases like cystic fibrosis are entirely genetic. Okay, so now you have a fair idea about infectious and non-infectious diseases at this point. So let's go back to that disease list and sort the diseases into the right category. We'll color the words in pink for the infectious diseases and yellow for the non-infectious diseases. Let's go. First up is typhoid. Typhoid is a bacterial disease that spreads through food and water. So that is an infectious disease. Then we have diabetes. Diabetes is the increase of sugar in the blood, something that a pathogen can't do. So it is a non-infectious disease. COVID in malaria are both infectious because they are pathogenic and they spread like wildfire. Cystic fibrosis is a genetic disease as we found out, so it is a non-infectious disease. Cholera is a bacterial disease that spreads through water, so again, infectious. Hypertension is increased blood pressure, not caused by a pathogen, so non-infectious. Now, this wouldn't be a biology lesson if we didn't have at least one exception. Cancer is that exception. Studies have shown that there are some viruses that can cause cancer. Yes, one of them is the human papilloma virus, which causes cervical cancer in women. So let's mark cancer in orange since it doesn't fit into one category strictly. And that's all about infectious and non-infectious diseases.