According to a new study led by neurologist Maria Lucia Brito Ferreira, MD of Restoration Hospital in Recife, Brazil, the Zika virus may be linked to an autoimmune disorder, acute disseminated encephalomyelitis (ADEM), that is similar to multiple sclerosis.1 ADEM is an immune mediated inflammatory disorder of the central nervous system that can be triggered by viral or bacterial infections or, more rarely, by vaccinations.2 3
The study in Brazil involved 151 patients who visited Restoration Hospital between December 2014 and June 2015. All of the patients had symptoms “compatible with arboviruses”—the family of viruses that includes chikungunya, dengue and Zika.1
All of the people came to the hospital with fever followed by a rash. Some also had severe itching, muscle and joint pain and red eyes. The neurologic symptoms started right away for some people and up to 15 days later for others.1
Blood tests showed that all the patients tested negative for chikungunya and dengue but positive for Zika.1
Six of the 151 patients subsequently developed neurologic symptoms consistent with autoimmune disorders affecting the central nervous system. Of those six individuals, two of them developed acute disseminated encephalomyelitis (ADEM)—described in the study as “swelling of the brain and spinal cord that attacks the myelin, which is the coating around nerve fibers.”1
Brain scans performed on the two patients revealed signs of damage to the brain’s white matter. The other four patients developed Guillain-Barré syndrome (GBS) described in the study as a “syndrome that involves myelin of the peripheral nervous system.”1 GBS in another immune mediated inflammatory neurological disorder that has been causally linked to viral infections and, more rarely, to vaccinations like influenza vaccine.4
Pointing to the results of the study, James Sejvar, MD of the U.S. Centers for Disease Control and Prevention (CDC) rhetorically asks, “[W]hy does Zika virus appear to have this strong association with GBS and potentially other immune/inflammatory diseases of the nervous system?”1
The Brito study does not answer this question. But a more fundamental question might be, does this implied strong association between the Zika virus infection and immune mediated neurological disorders like ADEM and GBS even exist? After all, of the 151 patients who tested positive for Zika virus, only six developed autoimmune disorder symptoms, including two with ADEM and four with Guillain-Barré. That’s only 4% of the patients in the study. This hardly qualifies as a strong association between Zika and anything.
Dr. Brito cautions that the results of her study do not “mean that all people infected with Zika will experience these brain problems.”1 She is correct—96% of the patients in her study did not experience brain problems. Furthermore, it is unclear whether other factors such exposure to toxic chemicals like pesticides or vaccines were ruled out for the 4% who did suffer brain problems. What is the scientific basis for assuming that the presence of the Zika virus in the tiny portion of patients with the brain problems is, in fact, the cause of the problems?
Dr. Brito’s small study may offer some interesting questions to explore with regard to the Zika virus. However, as Dr. Brito notes, “Much more research will need to be done to explore whether there is a causal link between Zika and these brain problems.”1
1 Zika Virus May Now Be Tied to Another Brain Disease. American Academy of Neurology (press release) April 2016.
2 Marchioni E, Tavazzi E, Monoli M et al. Acute disseminated encephalomyelitis. Curr Infect Dis Rep 2008; 10(4): 307-314.
3 Pellegrino P, Carnovale C, Perrone V et al. Acute Disseminated Encephalomyelitis Onset: Based on Vaccine Adverse Events Reporting System. PLOS One Oct. 13, 2013 (online).
4 Velozzi C, Iqbal S, Broder K. Guillain Barre Syndrome, Influenza and Influenza Vaccination: The Epidemiological Evidence. Clin Infect Dis 2014; 58(8): 1149-1155.