Protecting ourselves from infectious diseases
Teaching during a pandemic means sometimes fielding tricky questions. This article should equip you to know enough about microorganisms and how they affect us and our bodies to be able to respond with confidence.
We've been used to winter illnesses like colds and haven't really had to worry much about them. But the coronavirus pandemic has forced us to take measures to protect ourselves in our homes, places where we work and learn, and places where we meet others socially, because it is a new human virus and very infectious.
Our bodies are home to millions of microorganisms, most of which do us no harm at all. But there are some microorganisms which cause disease and our bodies have some amazing ways to help protect us from them.
Our first defence is our skin. It's a really tough barrier. Skin cells grow from the inside so the layer we can touch, the outermost layer of the epidermis, is actually a layer of dead cells. Viruses cannot replicate in dead cells but could be present on the surface of our skin. We might touch something that already has the virus on it – a surface that's collected some droplets from a sneeze, for example. When we breathe, eat food, or urinate, any microorganisms that might enter our bodies will come across a sticky mucous membrane – another barrier. The mucous traps microorganisms and prevents them getting further. We might sneeze to get rid of them from our nose, we produce enzymes to destroy them in the mucous too, and when we swallow mucous the strong acid in our stomach is another defence.
Although our bodies are amazing and protect us, we must still take action to protect ourselves and others. Viruses can't replicate on our skin, but they can pass from our hands into our mouths, or to someone or something else that another person might touch. Hand washing and good hygiene is essential to try to prevent microorganisms being spread unwittingly to others. Try the activity, How clean are your hands? and use the excellent resources from e-bug to explore this further.
How does our immune system work?
If a microorganism gets past the protective barriers in our bodies, our internal immune system gets to work. Our bodies are constantly under attack from microbes, parasites, allergens and other threats. The only reason we're not sick all the time is that our immune system deals with these assaults.
Vertebrates (that includes humans, remember!) have very sophisticated immune systems that adapt during a lifetime to take account of specific organisms and substances that enter the body. We call something that causes infectious disease a pathogen.
The first response involves an army of different white blood cells (lymphocytes) that recognise a pathogen. First on the scene are the natural killer cells - think of them as the alarm raisers - that will latch on to a pathogen, especially a virus, and release special chemicals that alert other cells. Next to arrive will be the white cells that can surround and engulf the pathogen and try to digest it.
Your blood carries these cells around all the time. You'll have seen their impact if you've ever had a thorn in your finger. It will become a little red and sore, perhaps even a little swollen. If you notice a little bit of whiteish pus, that's what is left after the white cells destroy any pathogens.
Another type of white cell begins the process that will lead to antibodies being developed. Helper cells first help our immune system learn to recognise the pathogen and B cells (called B cells as they are formed in our bone marrow) produce antibodies that bind to the pathogen and disable it. The B cells also remember the pathogen so that if it gets into our bodies again, they can very quickly produce antibodies and prevent an infection developing.
When we receive a vaccine, our bodies follow the same response. The vaccine mimics the pathogen and so our bodies develop antibodies to it. When we receive the coronavirus vaccine, our immune system will be able to recognise the virus if we do get infected in future and prevent us becoming ill.
E-bug, run by Public Health England, has lesson ideas and resources to help children aged 7-11 understand how our immune systems work and learn more about vaccinations. The ASE also produced lesson materials, Why you'll never catch smallpox, to work alongside a film centred upon the young boy whom Edward Jenner first vaccinated. Wellcome also has created an information hub about COVID-19 vaccines.
Image credit: Smiling doctor wearing PPE by Mix and Match Studio via Shutterstock SL