Core temperature
Fever – or to use its medical term ‘pyrexia’ – is defined as an increase in the body’s core temperature.
The body’s core temperature is 37’c, give or take, although various studies have shown that it can be anywhere in the range 36’c – 38’c and as a consequence 36.5’c – 37.5’c is often considered as the normal range. The body is exceptionally good at maintaining its core temperature – thermoregulation – and usually keeps it within a very narrow range of +/-0.2’c. This is known as the set point.
Any elevation in an individual’s temperature above the set point indicates fever. The current fearfest that has engulfed the nation and in particular schools groupthinks that any child “with a temperature” must have the killer virus of death. Ignoring the fact that a human without a temperature is dead and therefore all living humans must have a temperature, one presumes that the groupthink intends to mean ‘any human with an elevated temperature above normal’ has the killer virus of death. Not true, far from it.
Turn the tap off, I’m in the shower
Upon detection of an invasive pathogen, monocytes – a type of leukocyte or white blood cell – will attempt to destroy it through phagocytosis, in effect by eating it. Monoocytes form part of the body’s innate immune system, which is the first line of defence against infection. It is the always-on component, on the lookout 24/7 for any pathogen and unlike the second stage adaptive immune system, is not programmed to target a specific antigen.
With the immune system being so elegantly interconnected and focused upon a single objective – protect the body at all costs – monocytes also release cytokines, including pyrogens. Cytokines act like a fire alarm, both signalling that there is a fire and marking its location to aid the arrival of other members of innate immune system, such as neutrophils, the most plentiful of all the leukocytes. They also assist in the immediate immunoresponse, which is to trigger inflammation with its four key components of swelling, redness, heat and pain.
Pyrogens, in particular interleukin-1 (and to a lesser degree interleukin-6) and are sent to the hypothalamus, the part of the brain that is responsible for thermoregulation. Upon arrival, they fool the neuronal thermoreceptors in the hypothalamus into thinking that the body is colder than it is, which causes the hypothalamus to turn up the thermostat. Cue shivering and constriction of the blood vessels, which are induced to raise the set point.
Fever – what is it good for?
Many invasive pathogens are very sensitive to changes in temperature, so fever can inhibit the pathogen’s infectability or ability to replicate. A raised temperature also assists in the innate immune system’s response: remember that heat is one of the four essential components of the initial inflammmatory response. The biochemical action of the monocytes and neutrophils attacking the pathogen creates heat and the action of all these cells crossing over from the circulatory system into an infection site – a process known as diapedesis – causes the pain you feel, along with the build-up of fluid caused by the same process.
In addition, an elevated temperature assists in the warming-up of the second stage of the immunoresponse, the adaptive immune system. This involves the progamming of B cells to recognise the specific pathogen and then activating them in the primary and second lymph organs. This action is aided by an elevated temperature: next time you’re under the weather and you can feel your glands are up – swollen and sore – you are feeling the germinal centre of a secondary lymph organ making lots of B cells.
Finally, recent work on T cell trafficking [Chen et al] suggests that an elevated temperature helps T cell lymphocytes to get around more easily, allowing them to reach the location of an infection quicker as well as increases diapedesis.
Just the right temperature
Once the set point has been raised to an optimum level of approx. 39.5’c, it remains there to provide maximum support to the immunoresponse. Once the immune system has dealt with the pathogen, normal service can start to be resumed as the hypothalamus begins to return the body to its set point. This process of elevating temperature is an essential part of the body’s immunoresponse. It is triggered by any invasive pathogen – think how quickly an insect sting or bite shows the four signs of inflammation – and it is neither pathogen-specific nor unique to SARS-CoV-2.
As children have immature immune systems that are still developing and lacking experience, their immunoresponse will often – quite naturally – be exaggerated: think of the first times you tried to ride a wave when learning to surf or early days of riding without stabilisers: you wobble around way more than normal. So kids are more likely to have a high temperature in more situations than adults and to a greater degree.
School’s Out For Panic
Unfortunately, in this Great Insanity, any child turning up with the slightest sign of a cold, bug, ear infection or Twiglet in their lunchbox is immediately subjected to a temperature check, whereupon they and the whole of their academic year are all sent home and told to hide away for 14-days.
With an average secondary school having approximately 950 pupils, that means sending around 150 children home all because little Timmy stuck a pen in his ear a couple of days ago and has a bit of a temperature this morning. Cue localised hysteria, yet more enforced home schooling by parents acting as unpaid teachers while having to take yet more unpaid, unannounced leave from work.
A high temperature is a natural thing if you have any infection.
It does not mean your child has SARS-CoV-2 and in all likeliness doesn’t, given peak infections was now just under seven months ago.
If a whole year is sent home for two weeks every time a child has a high temperature, nothing approaching normality will ever be resumed as there will be continuous absences of overlapping academic years. Perhaps if the teachers didn’t get paid every time a year was sent home, we would witness the miraculous disappearance of the imaginary killer virus of death.
