What exactly is freshers' flu - and why do so many get it?

It's the second week of term. You've finally figured out how to use the washing machine, your flatmates are starting to feel like friends, and the whirlwind of freshers' week is behind you.

But just as things settle down, your throat starts to scratch, your nose runs, and suddenly lectures are less about learning and more about trying not to cough louder than the person next to you.

You were warned it would happen, but didn't expect it to hit quite so fast.

What's actually going on here? Why does everyone seem to get freshers' flu in the first few weeks of term? And why do so many say it feels worse than the average cold?

"Freshers' flu is just an assortment of common cold viruses that come and hit us all at the same time," says Dr Zania Stamataki, associate professor of viral immunology at the University of Birmingham.

It's not the actual flu, and it's rarely serious. But when thousands of students arrive on campus they bring with them a cocktail of respiratory viruses.

Add packed lecture theatres, dirty shared kitchens and late-night parties, and the result is a wave of illness that spreads quickly.

Sheena Cruickshank, an immunologist and professor in biomedical sciences at the University of Manchester, describes it as a "mixing pot" of infections.

"You're bringing people together from all over the world, putting them in close quarters, and exposing them to viruses they've never encountered before," she says.

Respiratory viruses are constantly evolving and even small differences between variants can mean the body's immune system doesn't recognise them, forcing it to start from scratch.

The immune system is the body's natural defence against infections. It's made up of a network of cells, tissues, and organs that work together to detect harmful invaders like viruses and bacteria, and help the body fight them off.

But during freshers' week your immune system is under-resourced and overworked.

That's because, as Prof Cruickshank explains, "your diet, your level of activity, your level of stress, and sleep are all factors that affect immune functions."

Which, she recognises, are "not necessarily the first focus" for students in the early weeks of university.

Among these, stress plays a particularly disruptive role. The pressure to settle in, make friends, manage new responsibilities, and keep up with academic demands can quickly become overwhelming.

This triggers the release of cortisol, a stress hormone that suppresses immune responses.

"We've all had those times when you're super stressed, you've got loads of deadlines, you work, work, work, you finish all the deadlines - and then you get ill," says Prof Cruickshank.

Stress can also impact the amount of sleep you get, which also impacts the immune system.

But for many students, the pressure to socialise and make friends during freshers' week outweighs the need to rest.

"I didn't want to miss out," says Imogen Farmer, 19, a second-year student at the University of Leeds.

She says she met up with friends every evening during freshers' week.

"I definitely suffered with it after the first week, like sore throat, runny nose, those typical symptoms, and it does linger for quite a while."

Imogen says it's been worth it because "so much of student culture, especially during freshers' week, revolves around nights out".

"That is how you meet a lot of people and bond with friends. So I did just say yes to everything."

But it's not just lack of sleep which makes life difficult for your immune system.

After drinking a lot of alcohol - which many students will be doing to overcome nerves - your body produces fewer white blood cells, which help to fight off infections.

"A lot of people have the misconception that if you're consuming alcohol, you sleep better. But you have higher stress and you sleep worse," says Dr Stamataki.

A poor diet can also weaken the immune system and, for many students, eating healthily isn't easy - especially when skipping meals is a regular occurrence.

With so many viruses around, you could be stuck in a lecture between two people who are sneezing, each infected with a different one. And you'd be exposed to both.

Viruses can then be passed on very easily, without you knowing (during the incubation period), and before you notice symptoms.

"Sometimes you think you've gotten away with it. And you haven't," Dr Stamataki warns.

"So you'll feel great. You'll go and play rugby, you'll hug your friends and you'll have a good time but at the same time, you'll be transmitting."

She says that the immune response within young people is "quite powerful" but it's limited by the fact they haven't been exposed to many viruses yet.

While everything you come across for the first time will make you sick, the next time you come across the same virus, the symptoms won't be as nasty.

You can also get two infections at once. This can help or hinder your body.

Either you'll start to feel really awful - because your immune system is struggling to cope - or your body's defences will start working overtime to deal with the invaders.

When that happens, the immune system "is already super pumped up," says Prof Cruickshank, because the body is busy making chemical messengers called cytokines that help to kill viruses.

If you're unlucky enough to get a second infection soon after you've got rid of the first one, it's usually because you're already rundown. That's when conditions like bronchitis can occur.

"If your symptoms are persisting for a really long time or you felt like you're getting better and then you get ill again, it might be worth getting some medical help just to check that," says Prof Cruickshank.

"If you see spots at the back of your throat, that's definitely a sign that you've got strep throat and you might need some antibiotics," she adds.

Viruses like colds and flu don't respond to antibiotics - these drugs are only used to treat some types of bacterial infection.

While most viruses are mild, some can be far more dangerous and meningitis is a serious infection to watch out for.

It can look a lot like freshers' flu, but if left untreated, it can lead to seizures, brain damage and sepsis.

One student, from Wolverhampton, had her lower legs and parts of her fingers amputated after being struck down with it a week after starting university.

Vaccines which help protect against various types of meningitis are given to children, but it's still important to be aware of the symptoms, even if you've had the jabs.

So what do you need to look out for?

Meningitis spreads in a similar way to a cold - through close contact with someone carrying the infection.

It causes inflammation of the membranes surrounding the brain and spinal cord, so if you recognise these symptoms, call 999 or go to A&E straight away.

For many students, the pressure to keep going, even when sick, is hard to ignore.

"You're pushing yourself so much because that's what you're being told to do," says Emily Valentine, a 19-year-old student at the University of Leeds.

"I tend to rest, but I know a lot of my friends try to push themselves to go to lectures, especially in the first week," she adds.

A shift to recording lectures during the pandemic has made it easier for students to catch up with work.

But experts say you should still give yourself time to recover.

"It can take your body a while to get over a really big assault from a virus," says Prof Cruickshank.