Disease is a massive threat to the population – there are lots of different types of disease, which cause different problems in people and spread in different ways. Some are very deadly, but don’t infect many people whereas some are not normally very dangerous, but infect lots and lots of people. One of the main problems is that diseases keep evolving and changing – for example, bacteria and viruses become resistant to the drugs we use to treat them, which makes it much more difficult to treat people infected with them. On top of this, we continue to find new diseases which have spread into the human population…examples of this from the past 30 years include HIV/AIDS, SARS and Nipah virus.
In the past, infectious diseases acted as a natural check on the human population….when populations started to get large, diseases could spread more easily, then every so often a large epidemic would spread through the population and kill a lot of people. An example of this is the 1918 flu pandemic (called the Spanish Flu) – the population were already in upheaval due to the war, nutrition levels were low due to rationing and the flu spread rapidly across the world. Flu changes a little bit every year, and this version of the virus was much more dangerous. It ended up killing up to 3% of the worlds population – that is between 50 and 100 million people…more than the first world war had killed!
Nowadays we have much better medicines and vaccines to prevent things like this from happening…so far we haven’t had any disease pandemics as bad as the 1918 flu, but the threat is always there. That is why there are scientists all over the world keeping an eye on what is going on, what diseases are spreading where, how many people are dying and also developing medication and vaccines in case they are needed.