Large Outbreak of Guillain-Barré Syndrome, Peru, 2019

Outbreaks of Guillain-Barré syndrome (GBS) are uncommon. In May 2019, national surveillance in Peru detected an increase in GBS cases in excess of the expected incidence of 1.2 cases/100,000 population. Several clinical and epidemiologic findings call into question the suggested association between this GBS outbreak and Campylobacter.

G uillain-Barré syndrome (GBS) is the most common form of acute flaccid paralysis worldwide (1). It is characterized by motor weakness, areflexia, sensory abnormalities, and cytoalbuminologic dissociation in cerebrospinal fluid (2). An upper respiratory or gastrointestinal illness typically precedes GBS (3). Campylobacter jejuni infection is the most frequently identified precipitant of GBS and usually is associated with the acute motor axonal neuropathy form of GBS (4).
During the week of May 26, 2019, the Peruvian Ministry of Health surveillance system detected several cases of suspected GBS that exceeded the expected incidence of 1.2 cases/100,000 persons/year (i.e., 29 cases/year) (1). Since 2016, hospitals in Peru have reported suspected GBS cases to a passive surveillance system (https://www.dge.gob.pe/portal/index. php?option=com_content&view=article&id=653). In early May 2019, when the system was modified to an active surveillance system because of increasing incidence, the National Center of Epidemiology, Prevention, and Disease Control solicited cases. Examining physicians classified cases in accordance with the Brighton Collaboration case definition for GBS (5).
The Instituto Nacional de Salud tested serum, urine, nasal swab samples, and feces for infectious pathogens using molecular panels for multipathogen detection (bioMérieux, https://www.biomerieux-diagnostics.com) and conventional microbiology assays.
This GBS outbreak was unusual because of the large number of cases. The incidence rate was nearly 25 times higher than expected (1) and higher than previously described GBS outbreaks. The rapid increase in numbers, followed by an equally precipitous decrease, might suggest a point-source exposure. The outbreak affected many geographically disparate  regions, including some that differed substantially in geoclimatic properties. General demographic features, such as slight male predominance and greater incidence with increased age, are typical for GBS (7). However, in many patients, a descending, rather than the more common ascending, paralysis developed (8). The clinical significance of this observation is unclear. Electrophysiologically, most cases appeared to have the acute motor axonal neuropathy phenotype of GBS, which has been closely associated with antecedent C. jejuni infection (9).
PCR and culture detected the C. jejuni outbreak reported here. Genetic analysis confirmed the clonality of these isolates recovered from affected regions of Peru and identified genotype sequence type 2993, which has been associated with GBS outbreaks in China (10). These results support the hypothesis that this unprecedented GBS outbreak was related to an antecedent Campylobacter outbreak with point source. However, diarrheal illnesses shortly before or during the GBS outbreak were not reported; previous GBS outbreaks associated with Campylobacter mostly have occurred in the context of larger outbreaks of symptomatic diarrheal illness (10). Because of the wide distribution of outbreaks in many geographically separated regions, we questioned how all areas were exposed to C. jejuni within a short time frame.
Limitations of our investigation included nonsystematic testing of samples and incomplete data on variables, such as hospitalization and clinical features. Epidemiologic investigations are ongoing to determine the potential antigenic source of the presumed infection, testing for Campylobacter-specific IgM and antiganglioside antibodies, additional isolate sequencing, and active surveillance for new cases.