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Immunity & Disease: fun facts and quiz
The essentials in 7 ideas, with fun facts, an illustrated story and a quiz to see how much you know.
The essentials
Germs
Germs are tiny organisms, or particles, that can cause disease. The main kinds are bacteria, viruses, fungi and parasites.
Key fact
Viruses are far smaller than bacteria.
Your Immune System
Your immune system defends you. Skin blocks germs, white blood cells attack invaders, and antibodies mark them for destruction.
Key fact
A fever is often a sign of the body fighting an infection.
Handwashing
Washing your hands with soap is one of the easiest ways to stop germs spreading. In the 1840s, doctor Ignaz Semmelweis showed it saved new mothers’ lives.
Key fact
Wash for at least 20 seconds.
Immune Memory
After fighting a germ, your body keeps memory cells that recognise it next time and respond faster. That’s why most people catch chickenpox only once.
Key fact
Vaccines train this memory without making you ill.
Epidemics & Pandemics
An epidemic is a disease spreading quickly in one region; a pandemic spreads across the world. The 1918 flu infected about a third of the world’s population.
Key fact
The WHO declared COVID-19 a pandemic in March 2020.
Antibiotic Resistance
Antibiotics kill bacteria, but overusing them lets resistant bacteria survive and spread. Using antibiotics only when they’re really needed helps slow this down.
Key fact
Antibiotics don’t work on viruses like colds and flu.
Allergies
An allergy is the immune system overreacting to something harmless, like pollen, peanuts or pet dander. Hay fever is one of the most common.
Key fact
Reactions range from sneezing to, rarely, dangerous anaphylaxis.
Fun facts
In ideal conditions, one bacterium dividing every 20 minutes could become billions in under 12 hours.
Tears contain an enzyme, lysozyme, that breaks down the walls of some bacteria.
In one study of public toilets, people washed their hands for only about 6 seconds on average.
Survivors of the 1918 flu still made antibodies against it when tested in 2008, 90 years later.
“Quarantine” comes from the Italian for forty days, how long ships waited in plague-era Venice.
Resistance is ancient: resistance genes have turned up in bacteria frozen in permafrost for 30,000 years.
Hay fever affects around a quarter of people in some countries.
Story: A Lesson from Constantinople
A Lesson from Constantinople
1717, Constantinople. Lady Mary Wortley Montagu, scarred by smallpox herself, sees local women protect children against it.
They scratch a little matter from a mild case into the skin. The children fall mildly ill, and never catch smallpox again.
Back in London in 1721, she has her daughter treated the same way, and helps spread the practice decades before vaccines.
True or false?
Tap your answer to see if you got it, and why.
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Question 1 of 10
Viruses are smaller than bacteria.
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True. Often a hundred times smaller.
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Question 2 of 10
White blood cells fight infections.
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True. They seek out and destroy invaders.
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Question 3 of 10
Handwashing helps stop germs spreading.
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True. Soap lifts germs off and water rinses them away.
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Question 4 of 10
Memory cells help the body respond faster to germs it has met before.
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True. The second response is quicker and stronger.
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Question 5 of 10
A pandemic spreads across many countries.
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True. Across continents, even worldwide.
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Question 6 of 10
Using antibiotics only when needed slows resistance.
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True. Fewer chances for resistant survivors.
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Question 7 of 10
Allergies are the immune system overreacting.
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True. To something that’s actually harmless.
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Question 8 of 10
Viruses are a kind of bacteria.
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False. They’re a different kind of germ, and far smaller.
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Question 9 of 10
Skin plays no part in protecting you from germs.
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False. It’s your first barrier against them.
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Question 10 of 10
Doctors accepted Semmelweis’s ideas on handwashing straight away.
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False. Many rejected them during his lifetime.
Keep going in the app
KnowSoda learns what you know and brings back what you’re about to forget. Immunity & Disease has 6 more ideas at the Advanced and Expert levels.
Sources
- NHS — How the immune system works and allergies
- World Health Organization — Antimicrobial resistance and COVID-19 timeline
- U.S. CDC — History of the 1918 flu pandemic
- Encyclopaedia Britannica — Ignaz Semmelweis, immune system
- World Health Organization — Smallpox eradication; measles
- The Nobel Prize — Physiology or Medicine 2018
