by Jose E. Martinez Rodriguez & Erich Schmutzhard
Zika virus is an arbovirus, member of the family Flaviridae, genus Flavivirus, which has created an important public health emergency in the Americas after an epidemic outbreak associated with nervous system disorders. Two lineages of the virus has been described, the African (first discovered in 1947) and the Asian, the latter one related to outbreaks in Micronesia (2007) and French Polynesia (2013-2014), from where it spread to Brazil causing a new outbreak in April 2015. After more than 1,000,000 suspected cases of Zika infection in Brazil in 2015, the virus has further spread with imported cases into USA, Europe and other countries. On February 2016, the WHO designated the Zika virus epidemic infection as a public health emergency of international concern.
An unusual increase in microcephaly has been reported in Brazil after October 2015 (3500 cases recorded in a week in 2016, compared to an average of 163 cases per year between 2010 and 2014). In addition to microcepahly, other congenital anomalies recently related to intrauterine Zika infection have been: reduction in cerebral volume, ventriculomegaly, cerebellar hypoplasia, lissencephaly with hydrocephalus, and fetal akinesia (Melo 2016). Evidences of vertical transmission are supported by the detection of the Zika virus genome in the brain of a fetus with congenital malformations (Mlakar 2016) and in the amniotic fluid of pregnant women with infants with microcephaly (Calvet 2016). A recent study following pregnant women infected with Zika virus has shown a risk of fetal abnormalities detected by sonography in up to 29% of cases (Brasil 2016).
After the Zika virus outbreak in the French Polynesia in 2013-2014, 42 patients were diagnosed as Guillain-Barre syndrome (GBS) compared to previous reports of 3-10 cases/year (Watrin 2016). Similar associations of Zika virus infection with unusual increases in GBS were later reported in Brazil in 2015 and in El Salvador in January 2016, supporting a temporal and spatial link with Zika virus circulation and GBS development. Currently, 19 countries have reported increased incidence of GBS and/or laboratory confirmation of Zika virus infection. However, the clear ethiopathogenesis underlying these cases is far to be understood.
Besides the established link between Zika infection and congenital anomalies and GBS, other neurological conditions have been additionally associated (e.g., meningitis, meningoencephalitis and myelitis). Exceptional cases of fatal Zika virus infection in non-immunocompromised patients have also been reported (Swaminathan 2016).
Epidemiological surveillance on Zika virus infection has been increased in areas where the virus is circulating. As a general recommendation, WHO advises national authorities to implement surveillance systems to detect unusual increases in neurological syndromes (i.e., GBS, Fisher syndrome, encephalitis, meningitis, menigoencephalitis) and congenital anomalies, preparing health services for neurological care in case of need. In this scenario, the organization of the 2016 Olympics Games in Brazil has raised concerns about their attendance advisability. However, after the 2016 Summer Paralympic Games closed on 18 September, WHO has not received any official notification of Zika cases associated with this event, assessing the individual risk of infection in travelers returning from as low, albeit not zero. The WHO continues to report new cases in the Western Pacific Region, but without elucidating whether this apparent increase of Zika infection is real or the result of enhanced surveillance. Concerning Europe, so far a total of 6 cases of non-mosquito-borne Zika virus transmission have been reported in France, Germany, Italy, Netherlands, Portugal, and Spain. Two cases of Zika-associated microcephaly and / or CNS malformations have been reported in Spain, in subjects who had travelled in Colombia and Venezuela.
Currently, there are no specific treatment neither antiviral nor vaccines for Zika virus infection. The epidemiological control of the disease is the most effective way and the major challenge to avoid spread of the disease. To note, besides the virus transmission by the Aedes mosquito, the virus can be present in human body fluids, potentially spreading through placenta, unprotected sex and via blood transfusion. As preventive measures, PAHO / WHO recommendations are based on taking precautions to avoid mosquito bites for anyone living or travelling to areas where Zika virus is circulating. Due to previous reported cases of sexual transmission of Zika, specific recommendations for pregnant women are extended to practice safe sex or to abstain from sexual intercourse with partners living in or returning from areas where local transmission of Zika virus is known for at least 6 months. Moreover, pregnant women should be advised not to travel to areas with ongoing Zika virus outbreaks.
Jose E.Martínez-Rodríguez, MD, PhD. Associate Professor of Neurology, Universitat Autònoma de Barcelona, MS Unit, Neurology Department, Hospital del Mar, IMIM, Passeig Marítim 25-29, Barcelona
Erich Schmutzhard, MD, DTM&H(Liv.), Professor of Neurology and Critical Care Medicine, Department of Neurology, NICU, Medical University Innsbruck, Austria
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- Melo AS, Aguiar RS, Amorim MMR et al. Congenital Zika virus infection: beyond neonatal microcephaly. JAMA Neurol 2016 (in press).
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