As mosquitoes continue to spread Zika viral illnesses across Central and South America, Brazil and a number of other countries are noting a perceived surge in the number of instances of Guillain-Barré syndrome. While the data is slim regarding the confirmed number of cases, it may be useful to look at what the “normal” number ought to be. Brazil, Columbia, El Salvador and the United States are included in this analysis.
Guillain-Barré syndrome  is a condition caused by the body’s immune system attacking the peripheral nervous system. The National Institute of Neurological Disorders and Stroke states that the cause is unknown. The condition may progress until the entire body is affected. The result can be serious, even fatal, if if interferes with breathing, the regulation of blood pressure or the functions of the heart. There is no cure for Guillain-Barré syndrome and there is no vaccine. Treatment consists of supporting the body’s functions and reducing complications, using “plasma exchange (also called plasmapheresis) and high-dose immunoglobulin therapy …”.
Causes of Guillain-Barré syndrome
According to the Merck Manual , in about two thirds of the cases, the onset of Guillain-Barré syndrome “begins 5 days to 3 wk after a banal infectious disorder, surgery, or vaccination.” Common infections that are prequel to the condition include “Campylobacter jejuni , enteric viruses, herpesviruses (including cytomegalovirus and Epstein-Barr virus), and Mycoplasma sp.”
The most frequently identified cause of GBS is Campylobacter jejuni infection, which has been identified in up to 41% of patients and is associated with more severe disease and prolonged disability.
Hughes and Rees 
Hughes and Rees note a varying incidence rate for Guillain-Barré syndrome of 0.4 to 4.0 per 100,000 of population. They state a median incidence of 1.3 cases per 100,000.
Additional links about various infections associated with Guillain-Barré syndrome:
- Neuromuscular Manifestations of West Nile Virus Infection
- Guillain-Barre syndrome occurring during dengue fever
- Chikungunya Fever: An Epidemiological Review of a Re-Emerging Infectious Disease
- Guillain-Barre syndrome associated with rubella
- Two cases of Guillain-Barré syndrome and encephalitis after measles
West Nile was identified in NE Brazil in 2014. NE Brazil had a measles epidemic in 2014-2015. Brazil is in the midst of a dengue epidemic as well as a chikungunya epidemic. While rubella has not been identified recently, the same low vaccination rate for measles that allowed the recent outbreak would have meant an equally low vaccination rate for rubella. Zika viral infections are not the sole possible source of cases of Guillain-Barré syndrome in Brazil.
Incidence of Guillain-Barré syndrome
Eight sources for incidence rates have been identified. All are per 100,000 of population. These are estimates of what the “normal” caseload of Guillain-Barré syndrome should be in these four nations.
|Population 2015 ||204,259,812||46,736,728||6,141,350||321,368,864|
|CDC low ||1.0||2,043||467||61||3,214|
|McGrogan low ||1.1||2,247||514||68||3,535|
|Walling low ||1.65||3,370||771||101||5,303|
|Walling high ||1.79||3,656||837||110||5,753|
|McGrogan high ||1.80||3,677||841||111||5,785|
|CDC high ||2.0||4,085||935||123||6,427|
|GBS|CIDP Foundation ||2.0||4,085||935||123||6,427|
|U.S. military ||2.28||4,657||1,066||140||7,327|
- Guillain-Barré Syndrome Fact Sheet
- Guillain-Barré Syndrome (GBS) – Merck Manual
- CIA World Fact Book
- CDC General Questions and Answers on Guillain-Barré syndrome (GBS) 2009
- McGrogan A, Madle G, C, Seaman H, E, de Vries C, S, The Epidemiology of Guillain-Barré Syndrome Worldwide. Neuroepidemiology 2009;32:150-163
- Walling A, Dickson G, Guillain-Barré Syndrome. Am Fam Physician. 2013 Feb 1;87(3):191-197.
- GBS|CIDP Foundation International update on Zika virus and onset of Guillain-Barré Syndrome
- Nelson L, Gormley R, Riddle M S, Tribble D R, Porter C K, The epidemiology of Guillain-Barré Syndrome in U.S. military personnel: a case-control study. MC Research Notes 2009; 2:171. DOI: 10.1186/1756-0500-2-171
- Hughes R, Rees J, Clinical and Epidemiologic Features of Guillain-Barré Syndrome. J Infect Dis. (1997) 176 (Supplement 2): S92-S98. doi: 10.1086/513793
According to the Latin Post on Jan. 25, Brazilian authorities are noting an increase in cases of Guillain-Barré Syndrome. They are not, as yet, collecting any numbers. El Salvador is reporting 46 cases since Dec. 1. CBC, on Jan. 29, reported that Columbia has announced it has 41 cases that appear to be related to Zika viral illnesses.
The estimated “normal” number of cases of Guillain-Barré Syndrome in Columbia ranges from 467 to 1,066, and for El Salvador the range is 61 to 140. Both nations are experiencing the dengue and chikungunya epidemics.
As is being reported concerning microcephaly, an accurate diagnosis is essential. At this time, the data consists of reports and rumors. Columbia, for example, could merely be experiencing a normal number of GBS cases. El Salvador could be seeing an increase in GBS or just an increase in unconfirmed reports.
Worth noting, too, is that Brazil appears to normally have about three times more cases of Guillain-Barré Syndrome than cases of microcephaly. That suggests that the driving factor for GBS in Brazil is the large number of other viral illnesses that are rampant.