Zika virus has been known since 1947, but it was only with its spread to the Americas that it was declared a public health emergency of international concern by the World Health Organization (WHO)1. As Zika virus spread throughout South and Latin America, cases of babies born with microcephaly, where the head is smaller than normal, dramatically increased. Cases of Guillain-Barré syndrome increased as well2.
Guillain-Barré syndrome is a normally rare disorder in which the immune system attacks the peripheral nervous system. It can affect nerves that are responsible for muscle movement, as well as nerves that transmit pain, temperature, and touch. Symptoms of the disorder include muscle weakness and loss of sensation in the arms or legs. As the disorder progresses, it can lead to paralysis of the legs, arms, or muscles in the face. Some patients with Guillain-Barré syndrome will die from complications, though this is rare3.
As cases of Guillain-Barré syndrome increased in areas where Zika virus was newly introduced, it was suspected that the two were linked. However, conclusively proving that Zika virus causes Guillain-Barré syndrome is difficult. A strong piece of evidence would be if Zika virus were isolated from every patient with Guillain-Barré syndrome, but this has not been accomplished. Infection by Zika virus can be confirmed by blood or urine tests, but by the time a patient begins showing symptoms of Guillain-Barré syndrome, there may be no evidence of Zika virus left in the body2.
Diagnosing infection can be done in other ways, such as examining the patient’s symptoms or testing for immune response to Zika virus. However, in the case of Zika virus, these methods are complicated by viruses similar to Zika virus, especially dengue virus and chikungunya virus. Outbreaks of dengue fever and chikungunya have been reported in several South and Latin American countries that have had outbreaks of Zika virus disease4,5. In addition, all three viruses cause similar symptoms, and antibodies that are created against one virus can react to the other two viruses6. Thus, diagnosis of Zika virus based simply on the patient’s symptoms or immune response can be inaccurate.
While it has not been proven that Zika virus causes Guillain-Barré syndrome, a new study further supports the association between the two. The study took place in Colombia, which has had outbreaks of Zika virus disease, and examined patients with Guillain-Barré syndrome for evidence of Zika virus infection7.
Of these patients, 97% had symptoms that are seen in Zika virus infections, such as fever, rash, and headaches. 25% of the patients tested positive for Zika virus infection by laboratory testing. Other patients showed an immune response that could have been caused by Zika virus; however, infection by dengue virus would also have caused the same immune response6,7.
The investigators also showed an association between Zika virus and Guillain-Barré syndrome by examining epidemiological evidence. Before the introduction of Zika virus to Colombia, there were approximately twenty cases of Guillain-Barré syndrome per month in the entire country. During the outbreak of Zika virus disease, this number increased to ninety cases per month. Dengue virus has been present in Colombia for the past decade, and there was an outbreak of chikungunya in 2015, yet there were no increases in Guillain-Barré syndrome until the time that Zika virus was introduced in Colombia7.
The evidence from this study suggests an association, yet it still does not prove that Zika virus causes Guillain-Barré syndrome. Perhaps in the future, with better diagnostic tools, this causation can be proven.
This blog post is based off an original research article. You can read the original research article for free here.
1: Sikka V, Chattu VK, Popli RK, Galwankar SC, Kelkar D, Sawicki SG, Stawicki SP, Papadimos TJ. 2016. The emergency of Zika virus as a global health security threat: A review and a consensus statement of the INDUSEM Joint Working Group (JWG). J Global Infect Dis. 8(1):3-15.
2: Zika Virus: Overview [Internet]. 2016. Atlanta (GA): Centers for Disease Control and Prevention; [cited 2016 Oct 27]. Available from https://www.cdc.gov/zika/about/overview.html
3: Guillain-Barré syndrome [Internet]. 2016. World Health Organization; [cited 2016 Oct 27]. Available from http://who.int/mediacentre/factsheets/guillain-barre-syndrome/en/
4: Dengue: Epidemiology [Internet]. 2014. Atlanta (GA): Centers for Disease Control and Prevention; [cited 2016 Oct 27]. Available from http://www.cdc.gov/dengue/epidemiology/
5: Chikungunya Virus: Geographic Distribution [Internet]. 2016. Atlanta (GA): Centers for Disease Control and Prevention; [cited 2016 Oct 27]. Available from https://www.cdc.gov/chikungunya/geo/index.html
6: Mansfield KL, Horton DL, Johnson N, et al. 2011. Flavivirus-induced antibody cross-reactivity. J Gen Virol. 92:2821-9.
7: Parra B, Lizarazo J, Jiménez-Arango JA, Zea-Vera AF, González-Manrique G, Vargas J, Angarita JA, Zuñiga G, Lopez-Gonzalez R, Beltran CL, et al. 2016. Guillain-Barré syndrome associated with Zika virus infection in Colombia. New Engl J Med. 375(16):1514-23.