Spotlight on Zika – RCSIsmj staff writer Stephanie Tung
A recent announcement by the World Health Organization (WHO), declaring Zika virus as a “global public health emergency” has brought worldwide attention to this previously unheard of virus.1 Zika virus is classified as a member of the virus family Flaviviridae, which includes Dengue, West Nile, yellow fever and Japanese encephalitis virus.2 The virus is characterised as an arbovirus due to its vector based transmission via the Aedes genus of mosquitoes, which gives it the potential for rapid spread and could become endemic in some areas.2,3
Originally, the virus was mainly restricted to monkeys in the equatorial belt across Africa and Asia.2 The first reported outbreak of Zika was in 2007 in the Federated States of Micronesia with 49 confirmed and 59 probable cases.4 Outbreaks were also documented in four additional Pacific Island nations and some were associated with neurological complications, such as Guillain-Barré syndrome; however, there was also co-circulation of dengue at the time.5
In early 2015, the WHO confirmed the presence of Zika virus in the Americas and active transmission has since been confirmed in 28 countries including Brazil, Colombia, Venezuela, Mexico, Haiti and Barbados.6 The concern with the spread of the virus to the Americas is the intrinsic lack of population immunity, the lack of treatment or vaccine and the potential sequelae of the infection.2 Generally speaking, individuals infected with the virus only manifest mild symptoms such as fever, rash, arthralgia and conjunctivitis;, however, a report of an unusual increase in the number of microcephaly cases in Brazil coinciding with the spread of Zika virus has raised the alarm bells.2 Head circumference of less than 32 cm is used as a proxy measure for microcephaly.7 According to the latest epidemiological data, there have been 4180 suspected cases of microcephaly in Brazil since October of 2015 but only 270 have been confirmed and another 462 cases have been rejected.2
Admittedly, a causal relationship between the virus and these birth malformations has not been established and there is concern that the surge in microcephaly cases could be an artefact resulting from heightened surveillance and unspecific diagnostic criteria; however, more data is required before these factors can be teased apart.7
In light of this threat, the WHO has recommended that pregnant women consider delaying travel to affected areas and to take precautionary measures against the vector.8 Health authorities in certain affected countries have also recommended women to avoid pregnancy for the moment.8 To add fuel to the fire, evidence has emerged regarding potential sexually transmitted cases of Zika virus, which only further solidifies its status as a real infectious disease threat to watch out for.9
1.Pan American Health Organization WHO. WHO announces a Public Health Emergency of International Concern. 2016 [Available from: http://www.paho.org/hq/index.php?option=com_content&view=article&id=11640&Itemid=135&lang=en.
2. Samarasekera U, Triunfol M. Concern over Zika virus grips the world. Lancet. 2016.
3. Ayres CF. Identification of Zika virus vectors and implications for control. Lancet Infect Dis. 2016.
4. Duffy MR, Chen TH, Hancock WT, Powers AM, Kool JL, Lanciotti RS, et al. Zika virus outbreak on Yap Island, Federated States of Micronesia. N Engl J Med. 2009;360(24):2536-43.
5. Cao-Lormeau VM, Roche C, Teissier A, Robin E, Berry AL, Mallet HP, et al. Zika virus, French polynesia, South pacific, 2013. Emerg Infect Dis. 2014;20(6):1085-6.
6. Pan American Health Organization WHO. Countries and territories with autochthonous transmission in the Americas reported in 2015-2016. 2016 [Available from: http://www.paho.org/hq/index.php?option=com_content&view=article&id=11603&Itemid=41696&lang=en.
7.Butler D. Zika virus: Brazil’s surge in small-headed babies questioned by report. Nature. 2016;530(7588):13-4.
8.Torjesen I. Zika virus outbreaks prompt warnings to pregnant women. BMJ. 2016;352:i500.
9. McCarthy M. Zika virus was transmitted by sexual contact in Texas, health officials report. BMJ. 2016;352:i729./small>