At this time of the year, it seems like everyone in teaching has a cold. That’s unsurprising: schools are hotbeds for the transmission of disease.
But what happens when an infected student comes into the classroom? And how can we ensure that we teachers escape?
The common cold is not a single virus, it is a group of related viruses (mainly rhinoviruses), which live in the nose (they survive best at the temperature of the nasal passage, 33-35C, slightly below body temperature).
They cause similar enough symptoms, so we group them together. But the differences between them are why, no matter how many winters we teach in with our throats tickling and our noses streaming, we remain susceptible to the humble cold.
Catching a cold
The cold tends to be transmitted when "the afflicted" either cough or sneeze, and droplets of water containing live viruses are passed into the air.
Anyone within a metre is likely to breathe in some of these water droplets and then become infected with the various different types of cold virus, which enter the healthy cells in the nasal passage.
The viruses use different pathways, sometimes by latching on to receptors on the surface of the cell, or sometimes by being swallowed into an endosome because the cell thinks that the virus is food (the world’s smallest Trojan horse).
Once the viruses fuse, they hijack the cell’s apparatus to produce another load of viruses, and the pattern repeats.
And here’s the kicker: students who have picked up the virus can be infectious for 24 hours before they experience symptoms.
How to avoid a cold
So what would be the worst thing you can do as a teacher? Getting the students moving around so that they all have the opportunity to breathe in the air surrounding the as-yet-undiagnosed patient.
In a modern languages class, for example, a "speed dating" oral activity could be particularly damaging. If you really want to spread the infection, get the students all touching the same things – passing around their work for peer assessment, as infected water droplets can survive on hands for over five hours, and on surfaces for 24 hours.
Bingo. Another infected student.
Laboratory work is also great for this, especially if there is only one bottle of sulphuric acid for all of the groups to share.
Do any of this and all of the students will leave with a new friend living in their nasal passage, and start to exhibit symptoms over the next two-three days.
And yet so often it is the teacher who succumbs. It should be obvious by now why: we are the ones who move around, speak to every student and breathe in their infected air; it's us who collect their work, which is covered with the virus, and then rub our eyes with extreme exhaustion.
What can you do?
Invest in some sterile gloves, stick some Blu Tack up your nose and get creative with self-assessment so the little buggers (the viruses, not the children) don’t get passed around.
Then cross your fingers and pray.
Emily Seeber is head of science at Bedales School in Hampshire