Many countries face a mass migration every autumn. In the UK around 1.8 million young people leave their normal place of residence and move to a few hundred concentrated locations, where they often live and work at high density. Within a few weeks, it's common to hear reports that a significant proportion of them are ill with an infectious respiratory disease.
These migrants are undergraduate students and the disease is known colloquially as "freshers' flu". But seasonal influenza (A and B), which emerges from south-east Asia every year, doesn't normally arrive in the UK until December at the earliest. So freshers' flu is unlikely to be flu at all – although there's a small chance it could be the more obscure influenza C, for which there is no surveillance and therefore no information on seasonality.
Unseasonal outbreaks of respiratory diseases aren't that uncommon, but these are generally freak one-offs, like the presumed virus that struck down tennis players in the 2015 French Open. Freshers' flu, on the other hand, is regular enough to have entered the student consciousness as an annual fact of life. Whatever its causes, the phenomenon is a significant health burden on our universities, particularly for first-year students who may already be struggling to adapt to their new surroundings. This has left us with more questions about freshers' flu than we have answers.
Is it real?
Some might cynically suggest that hangovers and exhaustion play their part, but most academics are fairly convinced it is real, based on our experiences of watching the victims from the front of the lecture theatre. Despite the lack of research, most of our doubts are usually extinguished when we catch it ourselves.
After all, around 27.5 million working days are lost in the UK each year due to cold and flu-like illnesses.
Is there a single cause?
We know that cold and flu symptoms are caused by a multitude of different viruses. Recent work on genetic sequencing of a whole range of clinical and environmental samples –- an emerging scientific discipline known as microbiomics or microbial metagenomics –- has shown us that even apparently symptomless organisms are often hosting an interesting cocktail of bugs: viruses, bacteria and fungi.
We now have several respiratory microbiome datasets, some produced under conditions of experimental infection. Freshers' flu might simply represent an overwhelming of immune systems by things that are already there.
Is it the same illness every year?
One bad dose of the cold may seem much like any other. Freshers' flu might be something that hits the UK every year and that we have so far simply failed to look at closely enough. In the past, such things were technically quite difficult, but microbial metagenomics is changing that. The candidates other than flu might be coronaviruses, parvoviruses, enteroviruses or respiratory syncytial virus, all of which can cause the familiar constellation of symptoms that we know as "the common cold".
One other popular theory is that freshers' flu is caused when combinations of the above viruses from around the country and abroad suddenly arrive together in a place where there are plenty of unexposed susceptible potential victims. But as far as hard science goes, there is not enough evidence to really understand the origins and patterns of the condition (if it is one condition).
How can I avoid it and what should I do if I get it?
Protecting yourself against respiratory viruses is as much about hand hygiene as it is about avoid getting sneezed on. Make sure that your hands are washed immediately before you eat and try to avoid putting your hands in your eyes, nose and mouth the rest of the time. Avoiding large crowds is going to be difficult at university, but avoiding those individuals who are obviously ill might be slightly more feasible.
Eating properly, avoiding overdoing the alcohol, and getting enough sleep are fairly obvious ways to keep your immune system in good fettle, but then you may start to wonder if you are at university at all. If you do go down with it, there is little you can do other than stay hydrated and get through it. Not going out will help to avoid spreading it to other people.
Is the virus a candidate for vaccine development?
Despite these frivolities, universities take student health very seriously indeed. We are already vaccinating methodically against really dangerous student diseases such as meningitis. Freshers' flu might not be so life-threatening but it does diminish quality of life and decrease ability to study effectively. We now have the technology to investigate it, so we should get started.