Link Between Zika Infection And Guillain-Barré Syndrome Identified
Zika Linked with GuillainBarré Syndrome (GBS)
Between October, 2013 and April, 2014, French Polynesia experienced a severe Zika outbreak, described as the largest of its time. Simultaneously, an increase in the incidence of Guillain-Barre syndrome (GBS) was also recorded. These statistics led scientists to investigate the possibility of a link between the Zika virus and Guillain-Barre syndrome, suggesting a role of the virus and dengue infection in the development of Guillain-Barre syndrome.
Zika Linked With GuillainBarré Syndrome (GBS): Understanding the Basics
Zika virus was initially identified in 1947 in Africa, where it still causes regular outbreaks but very few clinical cases. The first reported full-blown epidemic occurred on the Micronesian island of Yap in 2007, spreading across the Pacific to Easter Island. In 2015-16, it again resurfaced in Americas and rest of the world leading W.H.O to label it as a global emergency threat. Zika virus is sustained within, with no prior vaccine and no definitive treatment availability, and spread to humans via the Aedesaegypti mosquitoes.
Guillain-Barré syndrome (GBS) is a common and highly severe form of acute autoimmune paralytic neuropathy, affecting about 100,000 people annually around the world. As is suggestive of the term ‘syndrome’, the disease consists of various distinctly recognizable clinical and pathological features, such as respiratory failure among 20-30 percent of cases. The symptomatic manifestation is usually always mild and self-limiting, with reports of fever, joint pain, rash and conjunctivitis. Along with supportive care, intravenous immunoglobulin or plasma exchange is the optimal approach for managing GBS. Advances in medicine have led to the initiation of many clinical trials investigating immunological and pathological mechanisms to develop new treatments.
Could There Be A Link Between Zika And GBS?
Guillain-Barré syndrome is regarded as a serious autoimmune illness occurring as a progressive paralysis over one to three weeks. A five percent death rate is associated with the illness, and about 20 percent of patients are left significantly disabled. Although rare, but various flaviviruses have also been found to trigger the syndrome, such as the West Nile virus, Japanese encephalitis virus, live-attenuated yellow fever vaccine and most importantly, the dengue virus.
Recent reports in the US suggesting an association between Zika and fetal deaths due to microcephaly, along with the serious neurological diseases such as GBS has triggered the World Health Organization (WHO) to declare the outbreak a global emergency. Hence, it was not a surprise when a tentative Zika-induced case of Guillain-Barré syndrome was recorded in French Polynesia in 2013.
The Study: Guillain-Barré Syndrome Associated With Zika Virus In French Polynesia
Van-Mai Cao-Lormeau and colleagues recently presented the first strong evidence that Zika virus infection could possibly cause GBS. The study is published in The Lancet.
The case-control study incorporated patients diagnosed with GBS from the Centre Hospitalier de PolynésieFrançaise (Papeete, Tahiti and French Polynesia) during a potential outbreak. Both, patients of GBS (cases) and individuals with a non-febrile illness or acute Zika virus disease without neurological symptoms (controls) were matched for age, sex and residence. Virological investigations and different immunoassays were performed to analyze the presence and activity of virus for both diseases.
A total of 42 patients were diagnosed with GBS during the study period, of which 41 (98 percent) had anti-Zika virus antibodies in their systems, whereas 100 percent of the patients had neutralizing antibodies against the virus. Moreover, 37 patients (88 percent) reported having a transient illness in a spell of six days before the onset of neurological symptoms, which is strongly suggestive of a recent Zika virus infection. All patients with GBS developed rapid clinical and neurological adversities, and 12 (29 percent) required respiratory assistance. No deaths were reported.
The above mentioned study demonstrates novel evidence that Zika virus infection could result in a potential epidemic of GBS as well. Due to the rapid spread of Zika infection across the US, other at risk countries need to develop adequate intensive care facilities to efficiently manage patients with GBS.
Since 88 percent of the cases reported by the researchers involved complaints of a preceding clinical illness, and since Zika was known to be symptomatic in only 20 percent of the cases reported in the Yap outbreak, an asymptomatic infection might pose a significantly lower risk of GBS as compared to infection with clinical symptoms. However, this can be assumed if the case-to-infection ratio in the French Polynesia outbreak is similar to that in the Yap outbreak.
What’s reassuring is that the study did not observe any evidence that a previous dengue infection increased the severity of GBS, which reduces the possibility of enhanced threats in areas of regular dengue activity.
Despite the strong associative evidence shown by the study, researchers warn that data is still limited to assume a complete causality. It is not known whether the present Zika virus is identical to that registered in previous outbreaks, whether it has a similar progression in different genetic and immune populations, or whether a potential co-infection or cofactor is responsible for the association.
In conclusion, it can be fairly stated that Zika virus can be included among the list of potential viruses causing GBS. Further investigations into cases of the syndrome must include tests for Zika, especially in areas where a significant risk of such an infections exists. Whether Zika virus will prove to enhance the incidence of GBS remains to be determined, but for now clinicians and medical experts must be vigilant and aware of a possible association, and should hence prescribe diagnostic tests and preventive regimes accordingly.