Germ vs. Terrain

When my daughter was two she contracted chicken pox. She was affected badly and we ended up spending the night in hospital as I couldn’t get her temperature down, but after a highly disturbed night were discharged the following morning, and she recovered quickly after that. A few weeks later though she started drinking as if water was going out of fashion, and waking regularly in the night to use the bathroom. The virus had triggered an autoimmune reaction which led to a diagnosis of type 1 diabetes.

We are not all affected equally

Now, why was she so badly affected when her sister was not? It was the same virus after all. True, she had probably got a bigger dose of virus in the first place, as she was likely exposed multiple times through being in the same house as her spotty sibling, whereas my eldest probably got one exposure from her nursery – but not everyone who has a bad dose of chicken pox ends up with type 1 diabetes. There must have been other factors at play – and this is where the terrain comes in.

In my daughter’s case, historic antibiotic use as a youngster had likely unbalanced her gut bacteria; she has a genetic predisposition towards autoimmunity which may not be shared with her sister; she was a picky eater and likely had intolerances to gluten and dairy right from early infancy which we didn’t know about (she has since been diagnosed as a coeliac). As we hadn’t modified her diet at all, she probably had a high inflammatory burden before she was infected; we live in the UK, and so it may well have been that her vitamin D levels were low as she was infected in November; she was a poor sleeper and used to wake at regular intervals throughout the night – pretty much every night…. All of these things would have affected her immune system functioning.

The germ did clearly play a role though – without the trigger she may still have a functioning pancreas (or something else may have triggered the condition by now) but this is just to say that how our bodies respond to an infection is in part dependent on how our bodies are functioning when we get infected.

Germs, terrain and respiratory infection risk

In the 1800s, Antoine Béchamp was the main proponent of this ‘terrain theory’ of disease, rivaling  Louis Pasteur, the champion of the germ theory. But the invention of the microscope and the ability to visualise microbes, helped the germ theory win the day – but denying that the terrain plays a role doesn’t make much sense.

We know that as we age, our immune resilience decreases, that socioeconomic status can increase your susceptibility to respiratory diseases, like flu (1) and being a peri-menopausal woman can increase your risk of “long-COVID” (more recently dubbed: post-acute sequelae of COVID) (2). These things we can do nothing about.

But other factors we can influence: Vitamin D status has been linked with risk from respiratory infections and autoimmunity (3) – and this is easily checked with a finger prick blood test and rectified with supplements or moving to sunnier climes. The Zoe COVID study from King’s College London recently announced that a higher quality diet, rich in fruit, vegetables and foods that nourish our gut bacteria can protect against catching COVID, whereas diets rich in ultra-processed foods were associated with poorer health outcomes (4). Stress hormones can suppress the immune system, and high and low blood sugars have been associated with poorer outcomes of COVID infection (5).

Improving resilience

For me, understanding the trajectory that led to my daughter’s diagnosis helped me come to terms with the situation, and gave me a challenge – what could I do to stop her getting further autoimmune diseases? Similarly the possibility that there are things we can do to affect our risk of being hard-hit by illness over winter, I find, helps remove some of the fear that comes from being threatened by a force that we are powerless to resist.

I would like to pass on the knowledge that I have gained about the immune system and how to support it – and so I have created a six-week course on Winter Wellness to help others make simple changes that can have big impacts. Do contact me if you would like to know more. We kick off on 7 November.


1) Cohen, S. (2006) ‘Social status and susceptibility to respiratory infections’ Annals of the New York Academy of Sciences
2) Crook et al., (2021) ‘Long COVID – mechanisms, risk factors, and management’ BMJ 374:n1648 doi:
3) Martens, P-J et al., (2020) ‘Vitamin D’s effect on immune function’ Nutrients 12(5) 1248
4) Merino, J et al., (2021) ‘Diet quality and risk of severity of COVID-19: a prospective cohort study’ Gut 70(11)
5) Shauly-Aharonov, M et al., (2021) ‘Both high and low pre-infection glucose levels associated with increased risk for severe COVID-10: New insights from a population based study PLOS ONE

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