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Guillain-Barré syndrome and Zika viral illnesses

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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

Guillain-Barré syndrome [1] 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 [2], 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 [9]

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:

  1. Neuromuscular Manifestations of West Nile Virus Infection
  2. Guillain-Barre syndrome occurring during dengue fever
  3. Chikungunya Fever: An Epidemiological Review of a Re-Emerging Infectious Disease
  4. Guillain-Barre syndrome associated with rubella
  5. 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.

Brazil Columbia El Salvador USA
Population 2015 [3] 204,259,812 46,736,728 6,141,350 321,368,864
Source Incidence Brazil Columbia El Salvador USA
CDC low [4]  1.0  2,043 467 61 3,214
McGrogan low [5]  1.1 2,247 514 68 3,535
Walling low [6]  1.65 3,370 771 101 5,303
Walling high [6]  1.79 3,656 837 110 5,753
McGrogan high [5]  1.80 3,677 841 111 5,785
CDC high [4]  2.0 4,085 935  123 6,427
GBS|CIDP Foundation [7]  2.0 4,085 935 123 6,427
U.S. military [8]  2.28 4,657 1,066 140 7,327
Mean  1.7 3,478 796 105 5,471
Median  1.8 3,666 839 110 5,769

    Discussion

    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.

    Sources and Citations

  1. Guillain-Barré Syndrome Fact Sheet
  2. Guillain-Barré Syndrome (GBS) – Merck Manual
  3. CIA World Fact Book
  4. CDC General Questions and Answers on Guillain-Barré syndrome (GBS) 2009
  5. McGrogan A, Madle G, C, Seaman H, E, de Vries C, S, The Epidemiology of Guillain-Barré Syndrome Worldwide. Neuroepidemiology 2009;32:150-163
  6. Walling A, Dickson G, Guillain-Barré Syndrome. Am Fam Physician. 2013 Feb 1;87(3):191-197.
  7. GBS|CIDP Foundation International update on Zika virus and onset of Guillain-Barré Syndrome
  8. 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
  9. 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

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