Narayan Gyawali; Richard S. Bradbury; Andrew W. Taylor-Robinson

“ The drivers responsible for Zika emergence and outbreak are evidently complex and multifactorial [43] . This collective knowledge gap demands urgent action to characterise better both the virus and the pathologies it causes, especially those related to infection during pregnancy, which represents a serious public health challenge. Beyond short term emergency management of the Latin American epidemic [6] , [7] , a major consideration is to research strategies for prevention of a global pandemic, including effective vaccine development and implementation of vector control programs. ”

“ In addition, increased globalisation continues to pose a risk for the spread of infection. Further, suspicions of alternative modes of virus transmission (sexual and vertical) , if proven, provide a platform for outbreaks in mosquito non-endemic regions as well. Since a vaccine or anti-viral therapy is not yet available, current means of disease prevention involve protection from mosquito bites, excluding pregnant females from travelling to Zika-endemic territories, and practicing safe sex in those countries. ”

“ While it is possible that the distribution of Zika in the Asia Pacific region could eventually reach as far as Australia, it should be containable in this and other developed countries where Aedes spp. mosquitoes are found through adherence to current measures of mosquito control. Such vector control programs are in place to combat dengue, yellow fever and Japanese encephalitis. It is highly likely that any outbreak initiated by an infected index case returning from overseas would be locally restricted, just like current dengue outbreaks that occur sporadically in northern Queensland [34] . ”

“ Moreover, as the region is presumed to be a novel location for Zika, the inhabitants will likely not have any prior exposure to ZIKV and thus will not have ever produced specific antibodies, which act as natural vaccine against the virus. In circumstances that are distinct from the sporadic infections which have arisen within populations in Africa and Asia for several decades, in the present Zika epidemic a substantial number of people must have been affected over a short period of time in order for the outbreak to expand rapidly from its initial localized focus of infection. ”

“ The recent striking emergence of cases of Zika in Latin America poses a threat for a worldwide outbreak of this mosquito-borne viral infection. The globalisation of the human population promotes the movement of asymptomatic carriers between countries in the same or different continents. Pregnant women are considered a high-risk group for Zika, as infection is strongly associated with, if as yet unproven as a cause of, microcephaly in the developing foetus. ”

“ Zika virus, an Aedes mosquito-borne flavivirus, is fast becoming a worldwide public health concern following its suspected association with over 4000 recent cases of microcephaly among newborn infants in Brazil.
Discussion
Prior to its emergence in Latin America in 2015–2016, Zika was known to exist at a relatively low prevalence in parts of Africa, Asia and the Pacific islands. An extension of its apparent global dispersion may be enabled by climate conditions suitable to support the population growth of A. aegypti and A. albopictus mosquitoes over an expanding geographical range. ”

“ As A. aegypti has a very limited flight range [35] , to sustain a significant outbreak requires a high population density of both mosquitoes and humans. In this context, it should be noted that this is a mosquito species that thrives in urban environments which is a consideration for future control programs, both for Zika itself but also in unison with the ongoing public health threat posed by dengue and other medically important arboviruses. ”

“ Until such time as the apparent association between ZIKV infection and microcephaly is either established or disproved, women should be cautious in planning to conceive a baby or to travel to a Zika-endemic country if already pregnant. ”