Chapter 12: Fever and Rest: When Germs Get In

When Germs Slip Past the Guards

Imagine waking up one morning and feeling that something is not quite right. Your throat feels scratchy, as if you swallowed a little bit of sand. Your nose is stuffy, and your head feels heavy on the pillow. Maybe you feel too warm, and then a moment later you feel shivery and want to pull the blanket up to your chin. You are not hurt, and nothing happened the day before. Still, your body is telling you that today is different.

What has happened is very common. Some germs have slipped past the guards you have read about in this book. Perhaps a few germs landed in your nose before the mucus could trap them. Perhaps germs traveled from your hands to your mouth while you were eating a snack. However they got in, the germs have started to make copies of themselves inside some of your cells, and your body has noticed.

This does not mean that your guards have failed. No castle in any story has walls so perfect that nothing ever gets through, and no body does either. Your nose, throat, windpipe and lungs stop a huge number of germs every day, far more than you could ever count. Once in a while, a few germs get through. When that happens, a second, deeper line of defense swings into action.

Most children catch several colds every year, especially when they spend lots of time with other children at school or at play. That is a normal part of growing up. Each time, the body learns something new about fighting germs. In this chapter, you will find out what is happening inside you when you feel sick, why your body sometimes heats up, and why rest is one of the best gifts you can give your guards.

Colds and Flu: Two Common Visitors

Two of the most common illnesses that affect the nose, throat and lungs are the common cold and the flu. Both are caused by viruses. Remember from Chapter 1 that a virus is a germ even smaller than bacteria, so tiny that it cannot be seen even with an ordinary microscope from a school science room. A virus cannot grow on its own. To make more copies of itself, a virus has to get inside one of your cells and use that cell like a little factory.

The common cold is caused by many different kinds of viruses, not just one. That is one reason why people can catch colds again and again. A cold usually begins with a sore or scratchy throat, then a runny or stuffy nose, sneezing and sometimes a cough. Most colds are mild. You may feel tired and grumpy for a few days, and then, little by little, you start to feel like yourself again.

The flu is short for influenza, which is said like this: in-flu-EN-zuh. The flu is caused by a different group of viruses. The flu often comes on more suddenly than a cold. A person with the flu may have a fever, aching muscles, a headache, a cough and a feeling of being very tired, as if their arms and legs were made of heavy stone. The flu usually makes people feel more unwell than a cold does, and it can take a bit longer to get better.

Colds and flu spread from person to person in similar ways. When someone who is sick coughs, sneezes or even talks, tiny droplets fly out of the nose and mouth. Other people can breathe in these droplets. The droplets can also land on hands, tables, toys and door handles. If you touch one of those places and then touch your eyes, nose or mouth, the viruses can hitch a ride into your body. That is why the next chapter is all about the simple habits that help stop germs from spreading.

It can be hard to tell one illness from another, even for grown-ups. Many different germs cause sneezes, sore throats and coughs. Working out exactly what is making someone sick is a job for doctors and nurses. What you can learn in this book is what your body does to fight back, which is the same clever plan for many different germs.

Why the Body Turns Up the Heat

Your body has its own thermostat, a little like the control on a heater that keeps a room at the right temperature. This thermostat is in a small part of the brain called the hypothalamus, said like this: hy-po-THAL-uh-mus. Most of the time, the hypothalamus keeps the inside of your body at about 37 degrees Celsius, which is about 98.6 degrees Fahrenheit. The exact number changes a little from person to person, and it goes up and down a bit during the day.

When your immune system, the body's whole team of germ fighters, discovers that germs have arrived, the germ-fighting cells send chemical messages through the blood. Some of these messages reach the hypothalamus. The messages tell the thermostat, "Turn it up." The thermostat raises its setting a little higher than usual, and the body starts to warm itself up. A body temperature that is higher than normal is called a fever.

At first, while your body is heating up, you may feel cold, even though you are actually getting warmer. Your body thinks it is too cold for the new setting, so it does what it always does when it feels cold. You shiver, because shivering muscles make heat. Your skin may look pale, because blood is kept deeper inside to save warmth. You want to curl up under a blanket. These feelings are called chills.

Later, when the fight is going well, the thermostat turns back down to its normal setting. Now your body feels too hot for the new setting, so it cools itself off. Your face may turn pink, and you may sweat, because sweat cools the skin as it dries. You might kick off the blanket. All of these changes are the body following the instructions of its thermostat.

Why would the body want to heat up at all? Scientists have found that a fever is part of the body's defense. Many germs grow best at your normal body temperature, and they grow less well when the body is warmer. At the same time, many of your germ-fighting cells work faster and better when they are a little warmer. So a fever is a bit like turning up the heat in a room to make it uncomfortable for unwelcome visitors while your guards get busier.

A fever can make you feel tired, achy and not hungry. That is not much fun. But it helps to know that, in most cases, a fever is a sign that your body is fighting, not a sign that something is going wrong with the fight. Grown-ups may use a thermometer to check how warm you are, and they keep an eye on how you are feeling. If a fever worries them, they can talk to a doctor, who will know what to do.

Runny Noses, Coughs and Other Busy Signs

When you are sick, many of the things you feel are signs that your guards are hard at work. It is a little like hearing lots of noise from a busy kitchen. The clatter and steam are not the problem. They are the sounds of people cooking.

Take a runny nose. When germs get into the lining of your nose, your body makes extra mucus. The mucus washes over the lining, trapping germs and carrying them away. At first the mucus is usually clear and runny. Later in a cold, it may become thicker and change color, sometimes to yellow or green, because it is now full of worn-out germ-fighting cells and the bits they have cleared away. Blowing your nose gently into a tissue helps move the mucus out, and throwing the tissue away helps keep germs from spreading.

A stuffy nose happens when the lining of the nose swells up. Germ-fighting cells and extra fluid gather there to fight, so the space for air gets narrower. Breathing through the nose may feel harder for a few days. This is the same kind of swelling that happens around a scrape on your knee: the body sends extra help to the place where it is needed.

A cough is the emergency exit at work. Mucus in the throat and windpipe gets pushed up and out with each cough, along with the germs trapped inside it. Sometimes a cough keeps going for a while even after the rest of a cold has gone, because the lining of the airways is still healing and stays a bit sensitive, like skin that is still tender after a scrape.

You may also notice small, soft lumps on the sides of your neck or under your jaw that feel a little sore when you are sick. These are the lymph nodes you met in Chapter 4, sometimes called glands. They are guard stations along your body's roads, where germ-fighting cells gather, share information and get ready to fight. When there is a lot of fighting to do, the lymph nodes fill up with busy cells and grow a little bigger. When the fight is over, they usually shrink back down.

Even feeling sleepy and not wanting to play is part of the plan. Fighting germs takes a lot of energy. When your body asks you to slow down, it is saving its strength for the guards. That brings us to one of the most important parts of getting better.

Rest: Giving Your Guards Time to Work

When you are sick, you might feel bored lying in bed or on the sofa. You might wish you could be at school with your friends or outside on your bike. But rest is not doing nothing. While you rest, your body is doing a huge amount of work on the inside.

Think of your body as a town with a limited supply of workers. On a normal day, many workers are busy helping you run, jump, think, learn and play. When germs invade, the town needs as many workers as possible on germ-fighting duty. If you rest, fewer workers are needed for running and jumping, and more energy can go to the fight. Rest is a way of sending your workers where they are needed most.

Sleep is especially powerful. While you sleep, your immune system is very active. Many of the body's repair jobs happen during sleep, and the germ-fighting team gets organized. This is why you may feel like sleeping much more than usual when you are sick. Your body knows what it needs.

Drinking enough is another way to help. When you have a fever, you lose extra water through your skin and your breath. A runny nose uses up water too. Sips of water, warm drinks, or a bowl of soup help replace that water. Enough water also keeps your mucus thinner and easier to move, so the escalator of tiny hairs in your windpipe can carry it away. A grown-up can help you choose what to drink and how often.

Staying home when you are sick does two good things at once. It gives your body the rest it needs, and it keeps your germs from spreading to your classmates, your teachers and other people around you. Some of those people might be babies, grandparents or people who are already unwell, whose bodies have a harder time fighting germs. Resting at home is a kind thing to do for yourself and for everyone else.

Being sick can also bring big feelings. You might feel sad about missing a party, cross about being stuck inside, or just miserable because your head hurts. All of those feelings are normal. It can help to listen to a story, look at picture books, draw quietly, or have a grown-up sit beside you for a while. Feeling cared for is part of feeling better.

When Grown-Ups Talk to a Doctor

Most colds get better on their own with rest, fluids and time. But your body does not have to do everything alone. Doctors and nurses are people who have studied for many years to understand how bodies work and what to do when someone is sick. They are part of the team that helps your guards.

The most important thing you can do when you feel unwell is to tell a grown-up. Say how you feel as clearly as you can: does your throat hurt, or your ear, or your tummy? Do you feel hot or cold, and is it hard to breathe? You know your body better than anyone else does, so your words are an important clue. You never need to be shy or worried about saying that you feel sick.

Grown-ups watch how you are doing and decide when to ask for help. A grown-up should talk to a doctor about any symptom that worries them. For example, a grown-up might call a doctor if breathing seems hard or very fast, if a fever is very high or goes on for many days, if a child is much sleepier than usual or will not drink, or if a child just seems much sicker than usual. These are only some examples. Grown-ups do not need a special reason: if they are worried, asking is always a good idea.

A doctor or nurse may look in your ears, mouth and throat, listen to your chest with a stethoscope, or check your temperature. The stethoscope is the listening tool you read about in Chapter 8, and it does not hurt at all. The doctor may feel the lymph nodes in your neck and ask you some questions. All of this helps the doctor understand what your body is going through.

Only a doctor or another trained health worker should decide whether you need any medicine or treatment. Medicines are chosen carefully for each person, so you should never take any medicine on your own or share someone else's. A grown-up will follow the doctor's advice. Your job is simple: tell a grown-up how you feel, rest, drink, and let your guards and your helpers do their work.

Getting Better: The Body Remembers

Little by little, the fight turns in your favor. Your germ-fighting cells destroy the infected cells and the viruses inside them. Antibodies, the special proteins you have read about before, grab on to the viruses so that the viruses cannot get into new cells. Antibodies are made by certain white blood cells, and each kind of antibody is shaped to fit one particular germ, like a key cut for one lock.

As the number of germs goes down, the alarm messages quiet down too. The thermostat in your brain turns back to its normal setting, and the fever fades. Your nose stops running so much. Your appetite comes back, and one morning you wake up and realize that you want to play again. Most colds last about a week, though a cough or a stuffy nose can linger a little longer.

Something wonderful remains after the fight. Some of the white blood cells that fought the germ stay in your body as memory cells, which you first met in Chapter 4. Memory cells remember what that particular germ looked like. If the same germ ever tries to get in again, the memory cells recognize it right away and call the guards much faster. Often, the germ is stopped before you even notice that you were exposed to it.

This is a little like learning to ride a bike. The first time is slow and wobbly, and you might need lots of help. After you have learned, your body remembers how to do it, and the next time is much quicker and easier. Your immune system learns in a similar way. That is one reason why children often catch more colds than grown-ups do: children are still meeting many germs for the first time.

Being sick is never fun, but it is a normal part of life, and your body is very good at getting better. Your guards at the gates catch most germs. When some germs get past, a deeper defense turns up the heat, sends extra workers and remembers the invader for next time. And all around you, grown-ups, doctors and nurses are ready to help. In the next chapter, you will discover how you can help your guards every day, with soap and water and with a clever kind of practice called a vaccine.

Key Words

Virus: A germ so tiny that it can only be seen with very powerful microscopes. A virus makes copies of itself by getting inside the body's cells.

Common cold: A mild illness of the nose and throat caused by many different viruses. It often brings a runny nose, sneezes and a sore throat.

Flu: Short for influenza, an illness caused by flu viruses. It often brings fever, aches, a cough and deep tiredness, and it usually feels worse than a cold.

Fever: A body temperature that is higher than normal. A fever is one of the ways the body fights germs.

Hypothalamus: A small part of the brain that works like a thermostat, keeping the body at the right temperature and turning it up during a fever.

Immune system: The body's whole team of germ fighters, including white blood cells, antibodies and lymph nodes.

Lymph nodes: Small, soft guard stations in places such as the neck, where germ-fighting cells gather. They can swell a little when the body is fighting germs.

Antibody: A special protein made by certain white blood cells. Each kind of antibody fits one particular germ and helps stop that germ from causing harm.

Memory cells: White blood cells that remember a germ after the body has fought it, so that the body can fight the same germ much faster next time.

Stethoscope: A tool that lets a doctor or nurse listen to the sounds of the lungs and the heart.