What Can Cause Guillain-Barré Syndrome
Guillain-Barré syndrome is primarily triggered by preceding infections in approximately two-thirds of cases, with Campylobacter jejuni being the single most common identifiable cause worldwide, followed by viral infections including cytomegalovirus, Epstein-Barr virus, hepatitis E virus, Zika virus, and Mycoplasma pneumoniae. 1
Primary Infectious Triggers
Bacterial Infections
The most important bacterial trigger is Campylobacter jejuni, which causes gastroenteritis and accounts for approximately 30-70% of GBS cases depending on geographic region 2. This bacterium is particularly prevalent in:
- Curaçao, China, and Bangladesh (60-70% of cases)
- Other countries (30-32% of cases)
The mechanism involves molecular mimicry between C. jejuni lipo-oligosaccharides and human nerve gangliosides, producing cross-reactive antibodies that activate complement and damage peripheral nerves 2.
Other bacterial triggers include:
- Mycoplasma pneumoniae (approximately 5% of cases) 1
- Haemophilus influenzae (particularly associated with Miller Fisher syndrome in Asia) 2
Viral Infections
Six pathogens have been definitively linked to GBS through case-control studies 1:
- Cytomegalovirus (10-13% of cases) - typically associated with demyelinating forms
- Epstein-Barr virus (10% of cases) - associated with demyelinating and sensorimotor variants
- Hepatitis E virus
- Zika virus - caused 20-fold increases in GBS during outbreaks in French Polynesia (2013-2014) and 3.2-5.1 times increases in Latin America/Caribbean (2014-2016) 2
- SARS-CoV-2 - associated with predominantly demyelinating subtype (77-80%) 2
Additional viral associations reported in specific regions include:
- Dengue virus (Southeast Asia and Brazil)
- HIV infection (sub-Saharan Africa)
- Enterovirus (Peru outbreak, 2018) 2
Clinical Pattern of Antecedent Infections
Upper respiratory tract infection is the most common antecedent event in Europe, North America, South America, and parts of Asia (22-53% of all patients, 50-70% in pediatric cases) 2.
Gastroenteritis is the predominant antecedent event in India and Bangladesh (36-47% of cases) 2.
The typical timeline: symptoms of infection occur within 4-6 weeks (most commonly 4 weeks) before onset of weakness 2, 1.
Non-Infectious Triggers
Vaccines
The 1976 "swine" influenza vaccine showed a definitive 7.3-fold increased risk of GBS 1. However, subsequent influenza vaccines show minimal risk:
- Approximately 1 additional GBS case per 1 million vaccinations
- No other vaccines have been convincingly linked to GBS 1
Immunobiological Agents
Rare associations reported with:
- Tumor necrosis factor antagonists
- Immune checkpoint inhibitors
- Type I interferons
These are based on case series and biological plausibility rather than definitive epidemiological evidence 1.
Other Temporal Associations
Surgery and malignancy have been temporally related to GBS, but lack clear biological rationale and strong epidemiological evidence 2, 1. The underlying mechanisms remain unclear.
Important Clinical Caveats
Risk Magnitude
Despite strong associations, the absolute risk of developing GBS after infection is extremely small:
- Only 1 in 1,000-5,000 patients with C. jejuni infection develop GBS
- Only 2 in 10,000 patients with Zika virus infection develop GBS 2
Absence of Antecedent Illness
The absence of a preceding infection does not exclude GBS diagnosis, as putative infections or immunological stimuli can be subclinical 1.
Geographic and Host Factors
Risk factors influencing susceptibility include:
- Genetic polymorphisms in TNF and MBL2 genes 2
- Nutritional status - malnutrition alters immune responses 2
- Strain-specific factors - not all C. jejuni strains possess the carbohydrate mimicry required to trigger cross-reactive antibodies 2
- Hygienic infrastructure and environmental factors affecting pathogen exposure 2
Subtype Associations
Different triggers produce different GBS variants: