Rates of Zika virus have been increasing in many countries, with infection primarily coming from mosquito bites (although sexual intercourse now appears a likely factor, with the disease passed from a man to a woman). The disease is associated with several ill-health effects. To add to those previously reported, an association with a new autoimmune disorder has been reported.
Zika virus is a member of the Flaviviridae virus family. In most people, the disease is asymptomatic. With the proportion of the population who are affected (around one in four people) the disease causes little more than a mild illness known as Zika fever. This fever lasts for around four to seven days. In addition to a rise in body temperature, associated symptoms can sometimes include rashes, joint pain, and conjunctivitis.
The disease, discovered back in 1947, is transmitted by daytime-active mosquitoes of the genus Aedes. The possibility of catching the disease rises proportionately with the numbers and distribution of carrier mosquitos (that is the more mosquitoes in a given area, the more likely it is that a person will catch the disease).
Outside of the mild fever, the disease poses a risk to pregnant women, where there is a clear connection with infected women and babies born with abnormally small heads and brain defects (termed microcephaly.) Furthermore, Zika virus disease appears to be linked to a form of paralysis called Guillain-Barré syndrome.
To add to these conditions, medical evidence suggests Zika virus can give rise to a type of autoimmune disorder. This form of the disease attacks the brain’s myelin coating, in a similar way to multiple sclerosis. Myelin is a fatty white substance that surrounds the axon of some nerve cells; the material is necessary for forming an electrically insulating layer.
This association with an autoimmune response is the research outcome from a study performed by Dr. Maria Lucia Brito Ferreira. Dr. Ferreira is employed by the Restoration Hospital in Recife, Brazil.
With her research, Dr. Ferreira discovered that in a low number of cases, some people who become infected with Zika go on to develop specific neurologic symptoms. These symptoms include acute disseminated encephalomyelitis. This condition affects the brain and spinal cord, damaging myelin. Although there are no cases of fatalities, those infected take an average of six months to recover. The low-level cases are similar in number to those linking Zika virus disease to Guillain-Barré syndrome.
In a research note, Dr. Ferreira states that her findings do not “mean that all people infected with Zika will experience these brain problems. Of those who have nervous system problems, most do not have brain symptoms.” Nonetheless, the findings do raise further concerns about the effects of the virus on the human brain.
The results of the new Zika disease association have yet to be published, although the results of a study are set to be reported to the April 15 meeting of the American Academy of Neurology in Vancouver, Canada.
