Skip to story
ELI5 Yahaaa

Living things too small to see

What Are Germs?

Germs are tiny living things that multiply inside you and make you ill.

A person who feelsill Microbes multiplyinginside them
Too small to see, numerous enough to matter.
  1. Step 1 of 5

    They are alive, and very small.

    A full stop1 mm wideA bacteriumabout 1/1000 ofthat

    Thousands of bacteria fit across a full stop. They eat, grow and reproduce like any living thing — just at a scale you cannot see.

  2. Step 2 of 5

    They multiply by splitting.

    1 One splits intotwo2 Two into four3 Millions withinhours

    One bacterium becomes two, two become four. With a 20-minute doubling time, a single cell can become millions within a day.

  3. Step 3 of 5

    Illness is partly them and partly you.

    The germ's doing Damage to cellsYour body's doing Fever and aches — thedefence

    Some symptoms come from damage the microbes do; many — fever, aches, tiredness — are your own immune response working.

  4. Step 4 of 5

    Bacteria and viruses are not the same.

    Bacteria Living cells —antibiotics workViruses Not alive — antibioticsuseless

    Bacteria are living cells and antibiotics can kill them. Viruses are not really alive and hijack your cells — antibiotics do nothing to them.

  5. Step 5 of 5

    They spread by touch, droplets and food.

    1 Germs on hands2 Soap breakstheir outerlayer3 Water rinsesthem away

    Hands are the main route, which is why washing works so well. Soap physically tears apart the outer layer of many microbes.

    Most microbes are harmless or helpful. Your gut holds trillions that you genuinely need.

The short version

Germs are microscopic living things that multiply inside you, and much of feeling ill is your own defence at work.

Try it yourself

Press a clean finger onto a slice of damp bread in a bag, and an unwashed one on another. Compare after a week.

Topics