A stomach bug can trigger the immune system to attack its own nerves
About 30% of Guillain–Barré cases follow infection with Campylobacter jejuni, a common cause of diarrhoea. Weeks later, the immune system turns on the insulation of the body's peripheral nerves, and weakness creeps up from the feet and hands, sometimes within hours. Yet only a tiny fraction of people who catch the bacterium ever develop it.
Guillain–Barré syndrome is a rare autoimmune disorder, striking 1 or 2 people per 100,000 each year. It is named for French neurologists Georges Guillain and Jean Alexandre Barré, who described it with André Strohl in 1916. Typically it starts with numbness, tingling or back pain, then weakness that spreads symmetrically, peaking anywhere from half a day to more than two weeks later before levelling off in a plateau that most often lasts about a week.
The damage happens in the peripheral nerves. Their long axons are wrapped in myelin made by Schwann cells, and in the most familiar form white blood cells strip that sheath; in another form, antibodies attack the axon membrane directly. Two-thirds of patients had an infection beforehand, usually of the gut or airways. Besides Campylobacter, around 10% of cases trace to cytomegalovirus, and links exist with Zika and dengue. Which strain of Campylobacter someone meets may matter, because the molecules on its surface differ.
The acute phase can be dangerous. About 15% need a ventilator because breathing muscles weaken, and many experience swings in heart rate and blood pressure as the involuntary nervous system is drawn in. Children under six are often misdiagnosed at first, sometimes for up to two weeks. With prompt treatment, typically intravenous immunoglobulin or plasma exchange plus supportive care, most recover well, though recovery can take years, around a third keep some weakness and about 7.5% die worldwide.
Vaccines are part of the story, with nuance. After the 1976 swine flu campaign, 362 cases appeared among 45 million vaccinated people, an 8.8-fold rise over normal rates and an outlier since. The 2009 pandemic flu shot added about one case per million, and catching influenza itself is a bigger risk than the jab. Rare links have also been reported with the Shingrix shingles vaccine and some COVID-19 vaccines.
Source: Guillain–Barré syndrome
