Unit 5 · Germs, Vaccines and First Aid

Think about a spoonful of yogurt. It is full of living things, too small to see. They are called bacteria. Each one is just a single cell. You would need a microscope to see them.

Bacteria live almost everywhere. They live in soil, in water and on your skin. Millions live inside your gut. Most bacteria do not hurt you. Many help you digest food or turn milk into yogurt.

A few kinds of bacteria are germs. A germ is a tiny living thing that can make you sick. One kind of bacteria causes strep throat. Another kind can get into a cut and make it red and sore.

When you catch a cold, a virus is usually the cause. A virus is a germ even smaller than bacteria. The flu and chickenpox are also caused by viruses.

A virus cannot grow or make copies on its own. It must get inside a living cell. The cell it uses is called the host. Inside, the virus makes the cell build many new viruses. Then they spread to more cells.

Bacteria and viruses are both germs, but they are different. Bacteria are living cells. Viruses are much smaller and are not cells at all. This difference matters when doctors choose a medicine.

Maya sneezes into the air. Tiny drops fly out. If she has a cold, the drops carry the virus. A friend nearby can breathe them in. That is one way germs spread.

Germs also spread by touch. Someone coughs into a hand, then touches a door handle. The next person touches it and then rubs an eye. Germs can also ride in food that was not cooked well, or in dirty water.

Simple habits block these paths. Wash hands with soap and water for about 20 seconds. Cough or sneeze into your elbow. Keep food clean and cooked. Drink clean water. These habits cut down the chances of getting sick. This is called good hygiene.

Your skin is like a wall that keeps most germs out. But sometimes germs get in, like through a scrape on your knee. Then your body has a team ready to fight. That team is your immune system.

The fighters are white blood cells. They travel in your blood to where germs are. Some white blood cells swallow germs whole. Others make antibodies. Antibodies are like tags that stick to a germ so other cells can find it and destroy it.

Your immune system also remembers. After it beats a germ, some cells keep a memory of it. If the same germ comes back, your body can fight it faster. This memory is why many people get chickenpox only once.

Ana wakes up hot and tired. Her dad checks her with a thermometer. Her temperature is higher than usual. She has a fever. Her dad tucks her back into bed with a glass of water.

A fever is not a germ. It is one way your body fights germs. When germs get in, the body turns up its heat. Some germs do not grow as well in a warmer body. The heat may also help the immune system work.

A fever can make you feel tired and achy. Resting and drinking water help. Tell a grown-up when you feel hot or sick. A grown-up can check your temperature and call a doctor or nurse if needed.

A fire drill helps you practice before there is a real fire. A vaccine is like a drill for your immune system. It lets the body practice fighting a germ without getting very sick.

A vaccine holds a weak, dead or harmless piece of a germ, or instructions for making one. It is often given as a shot. The immune system sees it and makes antibodies. It also makes memory cells.

Later, the real germ may come. Now the body knows it. It can fight fast, often before you feel sick. This protection is called immunity. Your doctor or nurse can tell you which vaccines you need and when.

Smallpox was a sickness caused by a virus. It killed many people for thousands of years. In the 1700s, English farm families noticed something. Milkmaids who had caught cowpox from cows seemed safe from smallpox.

Edward Jenner, a country doctor, tested this idea in 1796. He put matter from a cowpox sore into a cut on James Phipps’s arm. Later, he exposed James to smallpox. James stayed well.

Jenner wrote a book about his tests in 1798. The word vaccine comes from vacca, the Latin word for cow. Today, doctors test vaccines with careful rules to keep volunteers safe.

After Jenner, many countries began to vaccinate people against smallpox. In 1967 the World Health Organization started a big push to end it everywhere. Health workers traveled to villages all over the world.

The workers found each new case. Then they vaccinated everyone around that sick person. This stopped the virus from finding new people. The last natural case was found in Somalia, in Africa, in 1977.

In 1980 the World Health Organization said smallpox was eradicated. That means it was wiped out in the wild. It is the first human disease ever wiped out. It took teamwork from many nations.

In 1928, a scientist named Alexander Fleming came back to his lab in London. He saw mold growing on a dish of bacteria. Around the mold, the bacteria had died. The mold made something that killed them.

That something became penicillin. It was one of the first antibiotics. An antibiotic is a medicine that kills bacteria or stops them from growing. Penicillin was made in large amounts in the 1940s and saved many lives.

Doctors give antibiotics for infections caused by bacteria, like strep throat. Only a doctor or nurse can decide if you need one. Take it just the way they say, and finish it if they tell you to.

Sam has a runny nose and a cough. He asks his doctor for an antibiotic. The doctor kindly says no. Sam’s cold is caused by a virus, and antibiotics do not work on viruses.

Antibiotics attack parts that bacteria have, like their cell walls. Viruses do not have those parts. So the medicine has nothing to hit. For a cold, rest, fluids and time usually help most.

Using antibiotics when they are not needed can cause a problem. Some bacteria learn to survive them. This is called antibiotic resistance. Using antibiotics only when a doctor says so helps keep them effective for everyone.

Jada trips on the sidewalk and scrapes her hand. It stings, and there is a little blood. This is a small cut. Knowing a few steps helps her feel calm. Helping someone with a small hurt is called first aid.

First, wash the cut gently with clean water. Soap around the cut helps too. This rinses out dirt and germs. Next, press with a clean cloth if it is still bleeding. Then cover it with a bandage to keep it clean.

Always tell an adult about a cut. An adult can check it. A cut that is deep, will not stop bleeding, or gets red, puffy and warm later needs a doctor or nurse.

Ben is reading when his nose starts to bleed. Nosebleeds happen often, especially when the air is dry. Most stop on their own with the right care. Ben knows what to do.

Ben sits up and leans a little forward. This keeps blood from running down his throat. He pinches the soft part of his nose, just below the hard bony part. He breathes through his mouth and keeps pinching for about 10 minutes.

Leaning back is an old habit, but it is not the best idea. Blood can go down the throat and upset the stomach. Ben tells an adult. If a nosebleed does not stop or came from a hard hit, an adult should get medical help.

Mia touches a hot pan by mistake. Her finger turns red and hurts. This is a small burn. A burn is an injury from heat, like a stove, hot water or the sun.

The first step is to cool the burn. Hold it under cool running water for several minutes, until it feels better. Do not use ice. Ice can hurt the skin more. Do not put butter or oil on it either.

Tell an adult right away. An adult can cover a small burn loosely with a clean bandage. A big burn, a burn on the face, or a burn with blisters needs a doctor or nurse.

In the United States, 911 is the number to call in an emergency. An emergency is when someone is in danger right now and needs help fast. The call is free from any phone.

Call 911 if someone will not wake up, cannot breathe, is bleeding a lot, or is badly hurt. Call if you see a fire. If a grown-up is nearby, get them first. If not, you can call.

Do not call 911 as a joke or a test. Helpers must be free for real emergencies. The person who answers is a dispatcher. The dispatcher sends police, firefighters or an ambulance.

Remember Rosa? When she called, she said what happened: Grandpa fell and could not get up. Then she gave her address. An address is the street name and number of a home or building.

Knowing your address is a big help. Practice saying it with a grown-up. If you are not home, look for a street sign or a store name. Say your city too.

Answer each question the dispatcher asks. Speak slowly and clearly. Do not hang up until the dispatcher says you can. The dispatcher may give instructions, like unlocking the door.

Little Theo finds a bottle under the sink and takes a sip. His big sister sees. She knows cleaners can be harmful. She gets their dad right away. She brings the bottle too.

Dad calls Poison Control at 1-800-222-1222. That number works across the United States, any time of day or night. Experts there tell callers what to do. A poison is something that can hurt the body if swallowed, breathed in or touched.

If the person will not wake up or cannot breathe, call 911 instead. To stay safe, never taste things you do not know. Medicines, cleaners and plant sprays should be kept up high or locked away.

Omar cannot eat peanuts. For most people, peanuts are just a snack. But Omar’s immune system treats peanuts like a germ. This is called an allergy. It is not his fault.

Things that cause allergies are called allergens. Common ones are peanuts, tree nuts, milk, eggs, bee stings and pollen. A mild reaction may be sneezing or an itchy rash.

A very strong reaction is called anaphylaxis. The throat may swell, and breathing can get hard. It needs help right away. Friends can help by respecting food rules and never sharing food without asking.

Some people with serious allergies carry an epinephrine pen. One well-known brand is the EpiPen. Epinephrine is a medicine that can quickly help with anaphylaxis.

The pen gives a shot, often into the outer thigh. Adults and trained helpers, like school nurses, use it. Some older kids learn to use their own pen with their doctor’s help. After it is used, call 911, because the person still needs a doctor.

Your job as a friend is to know the signs and get an adult fast. Know where your friend’s pen is kept. Never play with someone’s pen. It is real medicine.

In an emergency, your heart may race and your hands may shake. That is normal. Your body is getting ready to act. Rosa felt this too when Grandpa fell.

Slow breathing helps. Breathe in through your nose while you count to four. Breathe out slowly. One or two slow breaths help your brain focus. Then you can remember what to do.

Staying calm also helps the hurt person. A kind, steady voice helps them feel safe. You can say, "Help is coming. I am here." You do not have to fix everything. Your job is to get help.

Mr. Lopez keeps a red box in his classroom. It has a white cross on it. It is a first-aid kit. Inside are supplies for small hurts. Every student knows where it is.

A kit often has bandages of different sizes, gauze pads, tape, and wipes for cleaning. It may have gloves, a cold pack and small scissors. Homes, schools and cars can each have one.

Know where the kit is kept at home and at school. Check it with a grown-up to replace used supplies. A kit does not replace a doctor. It helps with small things and gets you ready.

At recess, Lily falls off the monkey bars. She is crying and holding her wrist. Her friend Noah wants to help. He tells her, "Stay here. I will get the recess teacher."

Getting a trusted adult is often the most important step. A trusted adult is a grown-up you know can help, like a teacher, coach, nurse or parent. Noah does not try to move Lily or fix her arm.

If two friends are there, one can stay while the other runs for help. Tell the adult what happened and where. Being a good helper means doing your part and letting trained people do theirs.