On 26 June 2023, the National Center for Epidemiology, Prevention, and Disease Control (CDC) of Peru issued an epidemiological alert due to an unusual increase in Guillain-Barré Syndrome (GBS) cases in different regions of the country. According to historical data (excluding the 2019 outbreak), the average monthly number of GBS cases registered is less than 20 suspected cases per month nationwide. However, between 10 June – 15 July 2023, 130 suspected cases1 of GBS have been reported. Out of these cases, 44 have been confirmed. 2,3 This increase in the number of observed cases is higher than expected. The Presidency of the Republic of Peru in early July 2023, declared a national health emergency due to the unusual increase and enhanced the implementation of public health responses. To date, the potential cause of the unexpected GBS incidence remains under investigation. WHO advises Member States to maintain the ongoing monitoring of the incidence and trends of neurological disorders, especially GBS, to identify variations against their expected baseline values and implement protocols for improved patient management. By closely observing and tracking these conditions, countries can effectively respond to any changes and ensure appropriate measures are in place to address potential public health concerns.

Description of the situation Between epidemiological weeks 1 and 28 (until 15 July 2023), a total of 231 suspected GBS cases were reported in Peru as defined by the National Center for Epidemiology, Prevention, and Disease Control (CDC) Technical Health Standard for Epidemiological Surveillance and Laboratory Diagnosis for GBS1 in 20 of the country’s 24 departments. Fifty-six percent of the cases (130 cases) were reported between epidemiological weeks 23 (10 June 2023) and 28 (15 July 2023). Since the start of the year, the highest number of GBS cases were recorded in seven of the country’s 24 departments: Lima and Callao (75 cases), La Libertad (39), Piura (21), Lambayeque (20), Cajamarca (17), Junín (12), and Cusco (10). As of 15 July 2023, 100 cases have been confirmed to be compatible with GBS 2,3, including four deaths (Case Fatality Rate (CFR) 1.7%). The age group most affected were adults ≥ 30 years (158 cases) while children under 17 years of age accounted for 19% of the cases (44 cases). More than half of the reported cases (133; 57.6%) were males. The preliminary clinical manifestations of the 130 cases reported between epidemiological weeks 23 (10 July 2023) and 28 (15 July 2023) include gastrointestinal infection, respiratory infection and fever. In addition, 72.3% of these cases (94 cases) presented with upward progression of paralysis as neurological manifestation, with other cases presenting with some type of sequelae. Samples were collected from the cases according to the technical health standard for epidemiological surveillance and laboratory diagnosis of GBS in Peru. Between epidemiological weeks 23 and 28, 22 samples were collected of which 14 (63%) were positive for Campylobacter jejuni (one of the most common risk factors for GBS) in samples from the departments of La Libertad (5 cases), Lima (4), Piura (3), Cusco (1) and Lambayeque (1), with the sample from Lambayeque further characterised as genotype Campylobacter jejuni sequence type (ST)2993. Epidemiology of the disease Guillain-Barré Syndrome (GBS) is a rare neurological disorder of variable clinical severity, including fatal outcomes. It is the most common form of acute flaccid paralysis worldwide and is characterized by motor weakness, areflexia (absence of muscle reflexes), sensory abnormalities, and elevated protein levels in cerebrospinal fluid (cytoalbuminologic dissociation). Most often, an upper respiratory or gastrointestinal illness typically precedes GBS. There is currently no known cure for GBS. However, people with GBS need supportive treatment, sometimes in intensive care and follow-up. Most treatments available can help manage the symptoms, support the recovery process, and potentially shorten the duration of the illness. Although most cases, even the most serious ones, fully recover, they can produce almost total paralysis. Campylobacter jejuni infection is the most frequently identified precipitant and usually is associated with the acute motor axonal neuropathy form of GBS. While this syndrome is more common in adults and in males, people of all ages can be affected. In 2019, Peru reported an unprecedented outbreak of GBS that affected several regions of the country, with almost 700 reported cases (incidence: 1.2/100,000 inhabitants). From the clinical-epidemiological characteristics and the study of the identified agents, it was concluded that the outbreak was associated with the presence of the Campylobacter jejuni sequence type (ST) 2993 genotype. In addition, during the year 2020, a total of 448 cases were reported nationally with a weekly average of 11 cases; in 2021, a total of 210 cases were reported with a weekly average of four cases. Similarly, in 2022, there were 225 cases reported with a consistent weekly average of four cases.