Hi there, I'm Mrs. Kemp and welcome to today's lesson all about bacterial and viral diseases in humans.

We're going to specifically talk about salmonella and measles today.

This fits into the health and disease unit, but you may also recognise some of the information from the diet and exercise unit.

Today, we will have the learning outcome, I can describe examples of common bacterial and viral diseases in humans, how they are spread and ways to reduce the spread.

These are some of the key terms that we're going to be using today, and if you'd like to read those in more detail, please do pause the video.

We have got three learning cycles for today.

We've got pathogens, pathogenic bacteria and pathogenic viruses, and of course we'll start with pathogens.

So actually what are pathogens? Okay, they can be viruses or bacteria or actually other microorganisms. And what they do is they cause a communicable disease.

Some of the types of pathogens then, like we said, include virus and bacteria.

It also includes fungi and protist.

Pathogens can actually infect plants as well as animals.

In fact, other organisms as well.

Pathogens can actually be spread from infected organisms to healthy ones, and this is why we call them communicable 'cause they can be passed from organism to organism.

Some of the ways that communicable diseases can be spread, then you can see that person sneezing there in the picture, that might give us a hint.

Actually, they can be spread through bodily fluids.

That can include blood, saliva, mucus, and semen, and also waste products such as faeces.

It can be passed from contaminated food or water, and we're going to see an example of that later, but also by touch, so one individual actually touching another individual may lead to the spread of a pathogen.

Okay, onto our first check, then.

This one is a true or false.

Pathogens are microorganisms that cause disease.

Is that true or false? Can you justify your answer? A, not all microorganisms cause disease or B, all microorganisms cause disease.

I'll give you a moment to think about it, but if you need more time please pause the video.

Okay, did you realise that that one was true? Well done, and that's because not actually all microorganisms cause disease.

Only the pathogenic kind.

Well done.

So not all microorganisms are pathogens, as we just mentioned.

Millions of bacteria actually live your digestive system.

We call those our gut flora and they have a really, really important job.

One of those is to help digest food that we couldn't digest ourselves.

So it means that when we eat food, it allows us to be able to break down and digest some things that actually otherwise we wouldn't be able to do.

They're also really linked with the health of our bodies, and depending on what kinds of bacteria we've got living down there may actually contribute to how healthy we are in other parts of our lives.

We also use bacteria to help make food and medicines.

So some of the bacteria might actually produce something that we can use as a medicine, for instance, insulin.

And other bacteria might be used to help make yoghourts and cheese, and they essentially help to produce products through fermentation, which we look at in other units.

Okay, which substances do bacteria help to make? A, apples, B, medicine, C, wood, or D, yoghourt.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay, did you get medicine and also yoghourt? Excellent, well done.

So onto our first task of the day then, If you want to get your worksheets out, you can record your answers on there.

Number one, what is a pathogen? Number two, name two types of pathogen.

Number three, describe how some microorganisms can be useful.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay, let's have a look at what we could have written then.

So of course, number one, a pathogen is a microorganism that causes a disease.

You may have put communicable disease in there.

That's also correct.

Number two, name two types of pathogen, any two from bacteria, fungi, virus or protists.

Describe how some microorganisms can be useful.

So our gut floor is made up of millions of bacteria and these can help us digest food that we cannot digest by ourselves.

We also use microorganisms to produce medicine and food such as yoghourt and cheese.

I hope you've got all those down.

If you need to add a little bit more, please do.

Onto our second learning cycle of today then.

This one is pathogenic bacteria.

Okay, so bacteria are known as prokaryotes, which means that they do not have a nucleus.

Let's have a look at a bacterial cell here.

We can see that it's got a long circular loop of DNA.

That's different to what we find eukaryotes, such as plants and animals where our DNA is actually contained inside a nucleus.

Bacteria when they are inside another organism will produce things called toxins, and toxins are essentially chemicals that cause harm to that individual.

They cause damage to the actual tissue and also make you feel unwell because of that toxin.

Salmonella is quite a well known bacteria and actually salmonella is the genus of the bacteria that is part of its classification and it's able to cause food poisoning.

It actually is found in the faeces of infected animals.

We can see chickens there living on a farm and where they live in very, very close contact to one another, they can pass that salmonella bacteria from one chicken to another.

It also means that there's going to be a lot of faeces in that area.

That actually may then mean that other individuals in that population actually become ill with salmonella as well.

So it's spread when food or water becomes contaminated with salmonella and that can happen at the farm as we've explained, also at the abattoir, that is where the animal is slaughtered and then prepared.

But also in the actual processing plant.

So where that chicken then goes to to be packaged up, and of course in your home kitchens or in restaurant kitchens, we can also see the spread of salmonella as well.

Which type of pathogen is salmonella? A, bacteria, B, protist or C, fungi? I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay, did you know that it was a bacteria? Excellent, really well done.

So when people actually ingest the contaminated food then, that has that salmonella bacteria on it or have some water that's also been infected, then they will have certain symptoms, things like vomiting, so being very violently sick, stomach cramps, having a really bad belly ache, having diarrhoea, a high temperature.

And most of the time in individuals actually these symptoms will usually pass within a week and you don't actually need any treatment.

You just need to make sure that you stay hydrated.

So keeping on drinking water whenever possible.

We can help to prevent the spread of salmonella.

We can vaccinate poultry, so that's what we do on farms. The chickens will be vaccinated to help slow down that spread.

Also making sure that when food is preferred, you follow basic hygiene standards.

So making sure that you've washed hands when you've handled uncooked or raw meat.

And then picking up other either like spoons or other pieces of food, making sure that your hands are clean, making sure that you wipe down surfaces really well, and also making sure that food has been cooked thoroughly.

Okay, one of the places where this can be a bit of a problem is maybe in the summertime at barbecue when potentially the barbecue's a bit too hot and you sort of burn the outside, but then the inside of that meat isn't cooked.

So it's always make sure that you either use a thermometer to test that it has reached the correct temperature or cut that food open and make sure that it is hot all the way through.

Okay, how is salmonella spread? A, bodily fluids, B, contaminated food or drink or C, touch.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Did you get B, contaminated food or drink? Excellent.

Really well done.

Okay, so onto our second task of the day, and just like the last one, we can record this on our worksheets.

Number one, describe some of the symptoms of salmonella.

Number two, explain why you cannot catch salmonella by standing close to someone with the infection.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay, let's see what we could have included in our answers then.

First of all, vomiting, stomach cramps, diarrhoea, and high temperature are all symptoms of salmonella.

Number two, salmonella is spread through contaminated food and drink that needs to be ingested.

Salmonella is not spread through bodily fluids that may become airborne.

Excellent, I hope you've got all those answers, well done.

Onto our final learning cycle of today then.

This is pathogenic viruses.

So viruses are actually not alive, okay? Because they cannot carry out all of the seven life processes without other cells.

They cannot respire or reproduce on their own.

They actually need a host cell to be able to reproduce.

Let's have a look at this little diagram then that shows a virus infecting a cell and then how it's actually sort of assembled and then how it's released.

So number one is showing that that virus is entering through the cell membrane into the cell.

The virus then uses all of the processes that are going on in that cell normally to actually get itself replicated.

So the cell in fact replicates the parts of the virus for the virus.

It then assembles that virus back into a particle and it bursts out of the cell.

When it bursts out of the cell, then it can lead to the cell actually dying, and this will cause damage to the host and make the host feel unwell.

Similar to other pathogens, viruses can actually survive for a long period of time outside.

So they can be sneezed out essentially, and then even when that mucus is sort of dried up, that actually would still be infectious if that got into somebody else.

They're also able to lay dormant in cells for long periods of time.

A good example of this is HIV, where actually the initial infection makes the person feel slightly unwell, but then actually that HIV can hide out in cells for about 10 years before they then actually start to cause more damage for that host.

So the host may not experience some symptoms sometimes even when you've had a virus for a really long time, and so actually you can be unaware that you've actually contracted a disease.

Okay, onto our next check.

Two students were discussing whether viruses are alive.

Who do you think has got the best answer? Laura has said, "I think viruses are alive because they are made of cells." Sophia has said, "I don't think viruses are alive because they cannot replicate on their own." I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay, did you realise that Sophia was correct? Excellent.

Really well done.

Can you match up each type of pathogen and how they cause damage to the host? So bacteria and virus, burst out of the host cells once replicated, produce toxins.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay, bacteria produces toxins and viruses, of course, they replicate inside cells and then they burst out.

Excellent, well done.

Let's have a look at an example then of a viral infection that affects humans.

This is measles and it is a highly infectious communicable disease.

That means that it is really easily spread around a population.

It usually occurs in early childhood and can have really serious complications.

There are some emergence of some measles actually affecting older people, but it really does affect children a lot more.

The initial symptoms are similar to a common cold, so things like high temperature, sneezing and coughing and runny nose.

So actually it's quite difficult to detect in those early stages and actually realise that it is different from just a normal cold.

After a few days though, usually not always, the individual will come out with quite a strong rash and we can see it in the image there.

And actually that's really characteristic of the measle infection.

It's spread by one person coughing or sneezing.

And when a person coughs or sneezes, just like you can see in that image, droplets of mucus actually enter the air.

Inside those droplets then you've got thousands of viral particles and they can be breathed in by other people and obviously then they're able to infect that person's cells and the person will have contracted that disease.

One of the ways that we can help to prevent the spread of measles then is by just following our normal hygiene standards, like making sure that we wash our hands.

If you are coughing and sneezing, make sure that you do that into a tissue and then you can throw them away.

If you are concerned that you have got measles, you should not attend nursery school or work because it can really be quickly spread around people.

The best way that we can stop the spread of measles is actually making sure that we have been vaccinated with the MMR vaccine.

The MMR is actually a combined vaccination against measles, mumps, and rubella, all things that can cause really devastating effects on young children.

So let's have a little think about actually how vaccines work to prevent the spread of diseases.

We're going to use some little faces in order to see who's being vaccinated then, that's that smiley face there, and so therefore that person is going to be immune to measles.

What that means is, is that that person will not be able to be infected by the measles virus because they already have the white blood cells needed to prevent that infection.

The pink unhappy faces, those are people that have not been vaccinated and therefore they are not immune to the measles.

And also the unhappy green faces, and these are people that actually have the disease.

So if none of the population is vaccinated, then it means that the disease can spread easily through the population because nobody has any immunity to this virus.

So anyone that comes into close contact with the person that is infected are likely to also then become infected.

If only a small percentage of people get vaccinated, actually the disease can still spread around that population.

It also means that people that have been vaccinated can still be a much lower risk, but still have a risk of contracting that infection if there are high numbers of people with that measles virus in the population.

The best way to prevent the spread is actually if most of the population are vaccinated.

So all of the individuals that are able to get the vaccination do do that.

This is something called herd immunity, which actually reduces the spread of that virus.

Okay, so it's important that when you are asked to go and get a vaccination, you do that in order to protect individuals in the population that are maybe not able to get that vaccination.

Okay, onto our next check then, which is the best way to stop the spread of measles? A, coughing into a tissue, B, getting vaccinated or C, washing hands.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay, that should be getting vaccinated.

Excellent, well done.

Onto our final task of the day, task C.

Again, you can record this on your worksheet.

Number one, explain why measles is a communicable disease.

Number two, what are the symptoms of measles? And number three, in 1998, Dr.

A, Wakefield made a link between the measles vaccine and an increased number of children with autism.

However, the study had many flaws and furthermore, rigorous studies have found no link.

Since the study, many parents have decided not to vaccinate their children.

How do you think this has affected the spread of the virus? I'll give you a moment to think about it, but if you need more time, please pause the video.

Let's have a look at what we could have answered then.

So number one, measles is caused by a virus and can spread from person to person.

If a person coughs or sneezes, the virus will be present in the droplets of mucus, which can be breathed in by someone else.

Number two, the person may experience a high temperature, sneezing and coughing, runny nose, and also a characteristic rash.

Number three then, how do you think this has affected the spread of the virus? So less people becoming vaccinated.

Many more cases of measles around the world, fewer people are immune, and so it spreads more easily.

The population is no longer protected by herd immunity.

I hope you've got all of those points down, but if you need to add a little bit more, please do.

So, we're nearly at the end, I'm just going to go through some of those key learning points for today.

So some microorganisms are pathogens and cause communicable diseases.

Some microorganisms do not cause disease, such as the ones that live in our small intestines.

Pathogenic bacteria produce toxins that damage living tissue and cause disease.

Salmonella is a type of bacteria that causes food poisoning.

It is spread through contaminated food and drink.

Viruses, invade cells to reproduce where they cause damage to cells.

Measles is a viral infection that is spread through droplets of mucus containing the virus being breathed in by another person.

I've really enjoyed learning with you today and I hope you have too.

I look forward to seeing you again soon, bye.