In 2015, Nikki Schultek was in her prime: a young mother of two little boys, she had just run a half marathon. Then, a mysterious illness hit. Her asthma, previously well-managed, became increasingly severe. Over the following months, she experienced chronic pain, digestive problems and a cardiac arrhythmia. Then came the “last insult”: signs of neurodegeneration, including brain fog and lapses of memory. “It was the lowest point,” she recalls. “I began making plans for my kids, writing down notes of things that I would want to tell them if I continued to get worse.”

Schultek received various diagnoses for individual problems, but none fully matched her constellation of symptoms. Eventually, one doctor suggested that an undetected infection could lie behind her chronic pain and breathing difficulties. She tested positive for Borrelia burgdorferi and Chlamydia pneumoniae infections and was prescribed a cocktail of antibiotics. On taking them, she found that all her symptoms – including the brain fog and memory deficits – went into remission.

Schultek has since founded a research group to explore the role of infection more generally in cognitive decline. This idea would once have been considered outlandish, but interest in the brain’s microbial community is growing rapidly. It turns out our grey matter is teeming with bacteria, viruses and fungi, and a better understanding of this unexpected microbiome has enormous potential to prevent neurodegenerative diseases. It could even reverse symptoms of decline when things go awry, as Schultek found. And, most excitingly of all, some potential treatments have a proven track…