ZIKA virus: interview with Dr Nikolaos Vasilakis
In this interview, reprinted from hiv-reservoir.net, Dr Nikolaos Vasilakis speaks to Dr Alain Lafeuillade about Zika virus in relation to the forthcoming 2016 InternationalSymposium on HIV and Emerging Infectious Diseases (ISHEID) being held in Marseille, France, 25–27 May.
Dr Vasilakis earned his BA and MA degrees in biology from Hofstra University. He worked for a number of years at Wyeth Research, where he developed vaccine candidates for paediatric diseases based on alphavirus gene delivery systems. Dr Vasilakis returned to academia to obtain his PhD degree from UTMB, studying sylvatic dengue in the lab of Dr Scott Weaver. After a brief postdoctoral position at the University of Pittsburgh, he came back to UTMB, where he studies the evolution and pathogenesis of arthropod-borne viruses, virus–mosquito, and virus–host interactions using sylvatic dengue as a model, for which with Malaysian collaborators he developed a field study in Borneo. Additionally, as a member of the World Reference Center for Emerging Viruses and Arboviruses (WRCEVA), he uses next-generation sequencing (NGS) to discover, characterise and annotate new and novel viruses that could lead to the development of successful countermeasures for a number of veterinary and human diseases.
Alain Lafeuillade (AL): Is the Zika virus new, if not, why is it in the frontline now?
Nikolaos Vasilakis (NV): Zika virus (ZIKV) was discovered in 1947 in Uganda during a serosurvey of yellow fever in non-human primates. Outbreaks of ZIKV disease (or Zika) have previously been reported in tropical Africa, southeast Asia, and the Pacific Islands. It entered in our conscience in 2007 when the first large outbreak occurred in the island of Yap. Following a number of outbreaks in French Polynesia and Easter Island, the virus emerged in Brazil in 2015, from where it spread rapidly throughout Latin and Central America and the Caribbean. In 2015, there were an estimated 1.5 million infections in Brazil alone.
ZIKV is at the forefront now because it has become a pandemic on a global scale and also due to the putative link between infection and fetus microcephaly in pregnant women.
AL: What is the current status of the epidemics?
NV: The reason(s) for the recent explosion of ZIKV in the Pacific and the Americas are not clear. Potential explanations include that ZIKV changed genetically and phenotypically during the past decade as it spread beyond Asia. This could involve selection for enhanced infection of its vector(s), higher levels of human viraemia in the urban cycle, which could also increase the efficiency of transmission as well as potentially enhance fetal infection or introduction into naïve populations at the right time and place for initiation of the human–mosquito cycle. Thus the spread of ZIKV in the New World has reached a pandemic level, where an estimated 4–5 million cases are estimated to occur. If the virus establishes an autochthonous transmission cycle in the United States, approximately 25 million people would be at risk of ZIKV infection.
AL: What is expected or feared about it and its spread?
NV: The rapid spread of ZIKV in the New World has been associated with a remarkable increase in microcephaly and Guillain–Barré syndrome cases. It is mainly the 20-fold increase in microcephaly cases that has caused concern for public health authorities and citizens alike.
AL: How is it transmitted? What is its natural reservoir?
NV: ZIKV is a arthropod-borne virus (arbovirus) whose major vectors of transmission are the anthropophilic Aedes aegypti and Aedes albopictus mosquitoes. In certain locations of southeast Asia, Aedes hensilii has also been implicated as a vector of transmission. There is also evidence that there is human-to-human transmission through sexual contact, but this is considered to be a negligible contributor to Zika transmission. In contrast to the human transmission cycle, there is an evolutionarily and ecologically distinct transmission cycle (sylvatic) occurring in the forests of Africa and possibly southeast Asia, where the virus circulates between mostly arboreal Aedes spp mosquitoes and non-human primates. In both cycles, primates are considered the sole amplification and reservoir hosts.
AL: How can we avoid its transmission?
NV: The prospects for controlling the spread of the current ZIKV epidemic are not promising. Until a vaccine is available, vector control and education of at-risk populations to reduce contact with the vector are the only short-term approaches available.
AL: How can we diagnose a case? Is there any test available in the clinic or are they for research only?
NV: Four out of five ZIKV infections are asymptomatic; symptomatic cases have the potential to be misdiagnosed as dengue, chikungunya or other infections with indistinguishable clinical presentations that include self-resolving fever, muscle and joint pain, conjunctivitis and/or rash. There is no licensed diagnostic test for ZIKV yet but there are molecular and serological tools available for the diagnosis of ZIKV exposure, which are for research only at this time.
AL: Is there a vaccine on the horizon?
NV: Currently several
groups are working for the development of a Zika vaccine based on established
platforms (attenuation, chimerisation, inactivation, etc), and it may take some
time to become licensed for human use.