Viruses are some of the smallest microbes there are, way smaller than bacteria. You cannot see them with an ordinary microscope like bacteria; you need to use a very special microscope to see viruses properly. Viruses are so basic that they are not even cells, just genetic material (genes) wrapped up inside a strong ‘coat’ made of protein. They cannot survive by themselves, viruses have to use a host to grow and multiply which makes them a type of parasite.
Some viruses are very clever. They don’t die off if they don’t have a host, they just hibernate (they become dormant) and wait for the right conditions to come along so they can make copies of themselves. Viruses can spread very easily from one person to the next just by touch or by sneezing or coughing when they fly out into the air in tiny water droplets. If a person doesn’t cover their mouth and nose when they sneeze or cough, you could breathe in their virus! Other viruses are spread when people are lazy about personal hygiene and they don’t wash their hands very often, especially when they have been to the toilet. Viruses also wait in areas you wouldn’t expect them to like door-handles or telephones so you should make sure to clean up after you and that you wash your hands regularly!
There are several thousand different types of viruses which use plants animals or even you as a host! Once a virus gets inside its host, it uses the hosts own cells to grow and make copies of itself. When a virus gets into your body and sees a cell it likes, it latches on and either injects its genes into your cell or your cell swallows it up. The virus then takes over the parts that make your cell work so it can make more copies of itself. These copies are identical to the first virus and usually, so many are made that your cell bursts! The new viruses spread to the cells next door and then the cells next to these, infecting your body bit by bit. Just one virus in your body can make thousands of copies of itself and make you very sick!
Viruses do lots of damage to their host and they damage normal healthy cells, causing disease. Some viruses cause diseases you will have heard of like measles, chickenpox and, of course, the flu! The flu (influenza) is one of the most famous viral diseases in the world. It affects your respiratory system and gives you cough, sore throat, runny nose, headache, fever, fatigue and pain. The flu is much more severe that a cold (which is also caused by a virus) although sometimes people do call a cold the flu! If the flu isn’t treated, it can lead to respiratory (breathing) difficulties, like bronchitis or pneumonia which is very dangerous in the very young, older people or people who are sick with something else already.
Scientists now know much more about how viruses like the flu work and viruses really are very clever. They can change themselves (mutate) very quickly so as soon as a new vaccine is made, a new type of flu appears that is just a little different from the last one! When a virus makes you sick, your immune system makes antibodies to help to fight the invaders. If the virus changes, even if it changes just a little, the antibodies made by your body don’t recognise it so you don’t have any defences to protect you. Viruses are different to bacteria which can be treated with antibiotics so there is no point taking antibiotics if you have a virus because they don’t work! The best defence against viruses is to be vaccinated before the virus gets a chance to get inside your body!
Viruses have different shapes but they are usually seen as large rods, spheres, or small, many-sided spheres. There are even viruses shaped like a spaceship! These are called bacteriophages and they infect and bacteria. Researchers and scientist are trying to find ways of using these viruses to fight bacterial infections that can be used instead of antibiotics.
The good viruses
There aren’t really many good viruses but a virus that did do some good was the vaccinia virus. In 1796, Dr Edward Jenner found that milkmaids infected with cowpox, a mild disease, did not get smallpox, a more deadly disease that only affects humans. Smallpox killed about 35% of people who were infected and left many people who survived with terrible scars on their skin. However, people that were first infected with cowpox were immune to smallpox! Dr Jenner invented the word ‘vaccination’ and his discovery led to the science of immunology. His work saved a massive amount of lives and led, in 1980, to the World Healthy Organisation (WHO) to declare that ‘the worldand its peoples’ were free from common smallpox. It is the only infectious disease in history to have been completely removed from nature by mankind!
Sometimes, being infected by a virus doesn’t mean you’ll get sick. A lot of adults have a virus called CMV – the cytomegalovirus – a member of the herpes virus family. You can get this at any time and it usually doesn’t make you very sick – sometimes it doesn’t make you sick at all. The virus lives in your body very happily but in its dormant state (so it is inactive, like its sleeping). It can still be very dangerous as it can wake up and cause problems if you are seriously ill or if your immune system is damaged. It is really important to keep fit and healthy so you can fight viruses that may be in your body if they decide to wake up!
Viruses have different shapes – they are most commonly seen as rods, spheres, or many-sided spheres. There are even viruses shaped like a spaceship! These are called bacteriophages and they infect and bacteria. Researchers and scientist are trying to find ways of using these viruses to fight bacterial infections that can be used instead of antibiotics.
The bad viruses
Viruses do lots of damage to the host and in humans they cause disease as they damage your normal healthy cells. Some viruses cause diseases you will have heard of like cold sores (caused by the herpes simplex virus), measles, chickenpox and, of course, colds and flu! Viruses can make you sick at the time but also for the rest of your life! The virus that causes chickenpox can hang around in your body and if you are stressed or your immune system is damaged, it can reappear when you are an adult as shingles, which are very painful.
There is no common treatment for viruses. They are not like bacteria that are killed with antibiotics. Antibiotics do not work on viruses, so there is no point taking them if you have a viral infection! As scientists find out more about how viruses work, there are some drugs being made that can treat some viral diseases, but these are pretty rare. The only really good way of protecting yourself against viruses is vaccination.
Being vaccinated means that the doctor will give you a tiny piece of a particular microbe that is dead, so that is safe. Vaccines won’t make you sick but it shows your body enough microbe to make sure your immune system would recognise it if it saw it again. Your body makes antibodies to the vaccine and you are then protected if that microbe ever tries to get past your first line of defence again!
Once you are vaccinated, you are immune to the microbe you have been vaccinated against. You have to be vaccinated for each new microbe you need to become immune to, but sometimes a couple of vaccines are mixed together so you can do a couple at once! Usually, when you are immune to a microbe, if it invades your body again you won’t get sick. Every so often though, a microbe that you have been vaccinated against will invade your body and make you a little sick. It is better though than having no defences because you are sick for a shorter time and you won’t feel as bad.
There are new viruses being discovered all the time so you probably will get sick from a virus at some stage! If you take care that your personal hygiene is good, your environment is clean and you are fit and healthy, you won’t feel too bad and will recover more quickly. Take care when you are sick, not to pass it on to others – just rest and give your body a chance to recover!
The ugly viruses
Before scientists knew how viruses passed from one person to the next, many people died in pandemics – that is, a disease that spread throughout the whole world. From 1918 to 1919, a flu pandemic occurred. This was also known as the ‘Spanish flu’ and killed between 50 and 100 million people across the world – that’s 2.5% - 5% of the total population of the world at that time!!! The Spanish flu was unusual as it attacked young healthy people and it killed up to 20% of the people infected (most flu viruses are only fatal in about 0.1% of cases and these are usually the very young and the very old). The disease was first seen in the USA, in Kansas, and it spread to just about every place in the world. Not everyone was infected, only about 20% of the world’s population. Many places escaped because of quarantine (where infected people were separated from healthy people) and simply things like wearing facemasks.
Scientists now know much more about how viruses like the flu work but viruses really are very clever. They can change themselves (mutate) very quickly so as quick as a new vaccine is made, a new type of flu appears. Viruses are different to bacteria which can be treated with antibiotics so there is no point taking antibiotics if you have a virus because they don’t work!
There are lots of really ugly viruses out there, many of which mean that the patient will die. Viruses cause diseases like rabies which comes from the Latin word for ‘rage’ or ‘madness’. The rabies virus makes the brain swell up and causes so much damage that the infected animal or person can have foam coming from their mouths which makes them look like there are in a terrible ‘rage’. There is a vaccine for rabies and people who are infected can be cured if they are treated quickly enough.
Another well known ugly virus that causes a lot of fear when its name is mentioned is the Ebola virus. Ebola is also known as a hemorrhagic fever because of the symptoms it causes. When the Ebola virus enters a host, it can cause a high fever and internal or external bleeding (haemorrhage). Most people who catch the Ebola virus die because it spreads so quickly and easily. Usually, the virus gets into as many hosts as possible until there are no hosts left. It then dies out but scientists don’t know what happens next. Sometimes Ebola just appears out of nowhere after years of hiding but it is not known where it goes or how it gets from place to place. Usually, the Ebola virus causes lots of problems in the very poor areas of the world, where hospitals and hygiene are not as good as in the developed world.
Some of the ugliest viruses are actually viruses that are quite common now. When the world was a mystery to most people, there was very little travel from one place to another. That all changed when technology was invented that allowed people to travel great distances by sea. Explorers found the ‘new worlds’ but brought a very unwelcome gift with them – disease. The explorers brought diseases that were very common in their home country but that had never been seen in the country they ‘discovered’. The native people of the new worlds did not have any immunity or protection from diseases like flu, smallpox, measles…lots of different common diseases. There was no vaccination either, so entire tribes and populations were killed by simple diseases. Now that travel around the world is very easy, the same problem doesn’t exist although lots of people get infected with bacteria and viruses spread by spending long hours in the same space with lots of people! If one person is sick on a plane for example, other people on the plane will feel sick pretty soon too!
All in all, viruses are some of the cleverest microbes there are. There are new viruses being discovered all the time so you probably will get sick from a virus at some stage! If you take care that your personal hygiene is good, your environment is clean and you are fit and healthy, you won’t feel too bad and will recover more quickly. Take care when you are sick, not to pass it on to others – just rest and give your body a chance to recover!
Not only are the parasitic viruses not animals or plants, they are not really even living organisms! Living organisms can survive without a host, whereas the parasitic virus cannot!
The word ‘virus’ comes from the Latin word for ‘poison’
People who study viruses are called virologists and the study of viruses is called virology.
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