Critical Review Of Literature On Zika Virus: Role Of Agent, Host And Environmental Factors, And Potential Policy And Response

Role of Agents

The viral strain of Zika virus, first underwent identification during the year 1947, amongst a population of monkeys in Uganda. The virus was later discovered in human populations as well during the year 1952, in countries of  United Republic of Tanzania and Uganda (Calvet et al., 2016). The viral disease strain is a flavivirus, borne out of mosquitoes and commonly undergoes transmission by the Aedes mosquito species, which is primary characterized to bite during daytime. The outbreak of diseases concerning this viral strain occurred across the African and Asian continents, during the years of 1960s and 1980s. However, disease epidemics of the same, have also been associated with the countries in America and the Pacific. The disease usually results in the occurrence of symptoms such as muscular joint pains, rashes, fevers, headache, conjunctivitis and a general feeling of discomfort and malaise, lasting for a minimum of two days to over one week (Oliveira Melo et al., 2016).

The following paragraphs of this essay, aim to focus upon the details of Zika virus, which proves to be a significant communicable disease threat in today’s world. The essay aims to critically review the literature available on the salient aspects of this disease strain. The upcoming sections shed light on the research available considering the role of disease transmitting agents, the various environmental and host factors involved in the disease transmission, policy frameworks and response strategies outlining its mitigation and eradication along with a final discussion concerning the future practiced which can be taken into consideration for management of this deadly virus.

As stated by the World Health Organization in its informative factsheet, the primary infectious agent responsible for disease transmission of Zika virus is the Aedes mosquito. Similar observations were also reported in a research conducted by the Oehler et al., (2014), outlining a case study of a woman from French Polynesia, displaying symptoms of Zika virus and further aggravated by Guillain-Barre Syndrome. Diagnostic results of the case study, highlighted the presence of symptoms similar to the viral strains of dengue. The respective authors of this research highlighted the arboviral nature of Zika virus, hence supporting the role of transmitting agents by arthropods, namely of the Aeges genus of mosquitoes (Oehler et al., 2014). However, due to lack of considerable research considering its incidence, and resemblance to symptoms similar to dengue or influence, symptomatic disease presentation in Zika virus patients, is often confused with dengue (Anaya et al., 2016).

Considering the role of vector agents in the transmission of Zika virus, the disease strain can be referred to as an ‘arbovirus’, as stated by Fauci & Moren (2018), in The New England Journal of Medicine. The term ‘arbovirus’ implies an umbrella background for numerous viral strains undergoing transmission by arthropods, such as ticks and mosquitoes, and are characterized by their role of rapid transmission as highlighted by the authors, through carefully offspring implantation in  bird and mammalian bodies, with the aid of activities like blood-feeding. The present day pandemic effect of Zika virus is astonishing, considering its obscure history, making it a relatively unknown strain until its discovery in Uganda during the early 1950s (Fauci & Moren, 2018).

Host and Environmental Factors

Gao et al., (2016) considered the rapid disease transmitting role of agents concerned with Zika virus transmission, with the help of a mathematical modeling analysis. The concerned agent, Aedes aegypti, can be traced to outline its origins in the villages of African districts, when the concerned villagers actively engaged in the storing of water in vessels. Uncovered water sources prove to be a significant attraction for the concerned vector agents to lay their eggs resulting in rapid growth of a population consisting of infectious disease carrying vector agents, characterized by their role of transmitting infection amongst humans through feeding of blood. (Gao et al., 2016).

Despite the general asymptomatic features of Zika virus infection as highlighted by Fonseca et al., (2014), who highlighted the case study of a Canadian woman returning to Thailand, the presence of mild symptoms similar to dengue, is not uncommon. The role of the A. aegypti agent in Zika disease transmission is characterized through exhibition of dengue-like symptoms such as muscle pains, mild fever, eye pain, prostration and maculapapular rash (Fonseca et al., 2014). However, the stated asymptomatic nature of Zika virus infection has been contradicted by Brasil et al., (2016), through inspection of infected women with the help of reverse-transcriptase-polymerase-chain-reaction-assays, indicating possibilities of abnormal nervous system development, restriction of growth and possible death of the concerned fetus (Brasil et al., 2016).

Due to the recent sudden rapidity of the transmission of Zika virus, despite its previous unidentified profile as a potentially harmful arbovirus, there still lies considerable dearth of information and research concerning the various environmental and host factors positively favoring its transmission. Messina et al., (2016), aimed to highlight such disease-favorable environments in their research through the usage of a species distribution modeling map. The authors in their research, highlighted various areas possessing tropical and sub-tropical climates which have presented high incidences of the disease outbreak. Latin American countries of Columbia, Brazil and Venezeula were determined to be areas of highest susceptibility, followed by major portions of sub-Saharan Africa and certain regions of the North American continent namely the southeastern region of Texas, stretching towards Florida. Despite the lack of disease outbreaks in India, the climatic conditions of a major chunk of the subcontinent also presents favorable conditions (Messina et al., 2016).

The various climatic, environmental and behavioral factors favoring Zika virus disease transmission have been elaborately highlighted by Fuller et al., (2017), through screening of urine and sera samples of from various municipalities from Rio De Janeiro. The research uncovered a positive association between the occurrence of rainfall and the incidence of Zika virus infection. This can be due to the fact that the occurrence of monsoons results in increased accumulation of water bodies, which prove to be highly favorable for the laying of eggs and transmission of potential disease-carrying agents of offspring amongst the population (Fuller et al., 2017).

In addition to the various environmental factors, numerous host factors are also responsible for the favorable transmission of Zika virus infection. The following research by Padilha et al., (2018) aimed to assess the various physiological, biological and behavioral aspects of the concerned vector of disease transmission. Such vector-oriented may prove to be beneficial in understanding the detailed causative factors underlying disease transmission, for the provision of optimum transmission of disease. The following research aimed to assess such factors through an investigative study, by artificial injection of Zika virus strains in female Aedes aegypti mosquitoes. The results indicated a lack of association between virus injection and activities outlining egg laying by the mosquitoes. However, there was a significant reduction in the movement and locomotion of the injected mosquitoes, which possible increases the chances of infection transmission in crowded, clustered households characterized by restricted movements (Padilha et al., 2018). However further research is required to validate this information as critically acclaimed in the research conducted by Russell et al., (2016), which states that a reduction of locomotion in mosquitoes consequently after conductance of blood feeding activities is considered normal due to increased blood metabolism, unrelated however to viral injection, which is necessary for the performance of oviposition or egg-laying activities (Russel et al., 2016).

Policy and Response Strategies

Further research conducted by Rodriguez-Morales (2015), aimed to highlight additional host factors for Zika disease transmission, the most common of which include the susceptibility of the mosquitoes to breed in water bodies or containers which are open, along with exhibition of peak biting behaviors during early evening and early morning hours. Identification of such factors prove to be useful in the future treatment and assessment of Zika virus infections (Rodriguez-Morales, 2015).

One of the key policy frameworks as a response to the rising occurrences of Zika virus can be observed in the Interim Guidelines for Prevention of Sexual Transmission of Zika virus, by the Centers of Disease Control and Prevention, as observed in the Morbidity and Mortality Weekly Report prepared by Oster et al., (2016). Despite the asymptomatic characteristic of the disease, Zika virus acquired during the stages of pregnancy have been found to yield fatal implications on the developing fetus, such as congenital microcephaly, nervous system abnormalities and even death. The authors in this report, hence focused elaborately on such harmful health consequences, along with the possible preventive measures to be undertaken concerning the sexual transmission of Zika virus infection. In accordance to these policy guidelines, men and women inhabiting areas favorable for Zika virus tranmssion, must either avoid sexual intercourse or preferable utilize protective means such as condoms. The concerned partners must also discuss amongst themselves the possibilities of case history, symptom presentation and vector transmission exposure before engagement in acts of intimacy (Oster et al., 2016).

As outlined previously in the preceding paragraphs, the occurrences of vector-borne diseases such as Zika virus, are characterized due to their rapid transmission, especially in areas associated with excessive crowding or mass gathering of populations. The prevalence of individuals accommodated in crowds or clusters have proven to be favorable in the transmission of harmful infectious diseases. With the sudden increase of Zika virus occurrences in latin American as well as North American countries, especially in Brazil in the year 2015 – the World Health Organization promptly declared the situation as a medical emergency at the global level, for which immediate public interventions is of utmost importance for its management and prevention (Trösemeier et al., 2016).

In a research review conducted by the Peterson et al., (2016) the authors aimed to assess the public response of Zika virus management during an emergency situation of its occurrence in Brazil during the Olympic Games. Upon overcome by a situation of medical emergency at the national and international level, the Emergency Committee for Zika virus management by the World Health Organization, recommended the usage of coordinated response at the global level. Such a response would be required for the improvement of detecting infections, surveillance of the disease profile, the occurrences of malformations congenitally and at the neurological level  for the purpose of reducing emergence of suspecting mosquitoes, hastening the creation of significant vaccines or treatment procedures and ultimately resulting in positive health outcomes of the global population (Peterson et al., 2016).

Codeço et al., (2016) in their research paper, highlighted elaborately and extensively on the active public response and policy frameworks undertaken by the Latin American countries like Brazil, especially during the sudden incidence of Zika virus disease transmission prior to the Brazil Olympics. Considering the possibilities of rapid disease dissemination due to the prevalence of clustered mass gathering during this major public even, the health officials and authorities of the Brazilian Government aimed to undertake active programs emphasizing on vector control. Such programs involved the active removal of areas or sources with the potential to enhance A. aegypti offspring, such as management of uncovered water sources and avoidance of excessive clustering of crowds. As an additional treatment response, the sports attendees and respective players of the Olympics were also required to interact with their respective local health or clinical setting or the Latin American Society for Travel Medicine in order to obtain considerable information about the prevention and management of harmful vector borne diseases, vaccinations required prior to traveling as well prophylaxis of malaria (Codeço et al., 2016).

Conclusion

The transmission of Zika virus still continues to exhibit situations of significant medical emergency, due to its possibilities of sudden occurrence along with possible exhibition of harmful symptoms. Zika virus infection has primarily been associated with the absence of symptoms of prevalence of mild, manageable symptoms similar to additional vector borne diseases such as dengue. However, the sexual transmission of Zika continues to plague the global community due to its exhibition of harmful symptoms pertaining especially to the child (Rasmussen et al., 2016).

Novak, Sheffield and Burd (2016), extensively highlight in their respective research concerning the lack of research and possible areas of future research. As per the current literature of known symptoms of Zika virus, there still lie considerable question regarding its chronic nature and possible similarities to dengue, influenza as well as diarrhea and hepatitis C. further current research has highlighted the detection of the virus in various bodily fluids such as semen, saliva, urine, blood, genital tract secretions as well as in the serum of women who are pregnant. Hence, this raises possible future questions concerning the appropriate method of detection to be used, especially in the situation of sexual transmission since the viral strain may be difficult to detect in the urine or blood sample. Thus, such lack of research paves the way for future recommendations of developing novel diagnostic and treatment techniques which will not only lead to accurate viral detection but also in the reduction of speed during pathogenic spread of disease. Additional, the authors stress on the need to develop sexual educational programs in order to impart public awareness concerning the various health implications associated with Zika virus infection and the required birth control methods (Novak, Sheffield & Burd, 2016).

Considering the possibilities of disease and resultant symptom severity Von Seidlein, Kekulé and Strickman (2017) assessed a variety of new intervention strategies associated with the management, prevention and treatment of the deadly infectious disease of Zika virus. One of the key novel strategies may be the utilization of the beds treated with insecticides, which proves to be feasible as well as convenient especially in homes. Such tactics have been formulated considering the tendencies of the disease vector agent to inhabit in closed spaces or indoors, especially during the daytime. Further the usage of outdoor fogging technique with the aid of substances such as permethrin and malathion has also proven to be novel tactic. However, such a technique may not be feasible in the future due to the unappealing visual characteristic of fogging and the potentiality to affect harmless organisms such as butterflies, honey bees and moths. Additional novel strategies which can prove to be beneficial is the dissemination of mosquitoes who have injected with a strain acquired from Drosophila flies, known as Wolbachia – which has been documented to hinder the transmission of harmful vector-borne diseases such as Zika, dengue, malaria and Chikungunya. An additional similar preventive strategy would be the creation and release of mosquito males who are sterile in order to prevent fertilization in the harmful females (Von Seidlein, Kekulé & Strickman, 2017)

Conclusion

Hence, as observed from the above critical review of literature, it can be rightfully state that despite its exhibition of mild symptoms, Zika virus continues to exhibit potential worry and public health burden, as a communicable disease burden. Due to similar modes of disease transmission along with exhibition of symptoms, infections caused due to Zika virus have often been associates with dengue or influenza. However, it is worthwhile to mention that the major agent playing a key role in the transmission of Zika virus, is the female Aedes aegypti mosquito, which is characterized by its laying of eggs in uncovered sources of water, sexual dissemination biting during the day as well as inhabiting crowded, clustered and indoor areas. Hence, public prevention and mitigation of this disease must be associated with active educational awareness considering the harmful symptoms, the requirement to undertake hygienic lifestyle activities as well as usage of protection during sexual intercourse. However, there has been considerable public response and policy interventions in the form of nationalized medical improvement especially in Brazil as well as with the possible development of novel strategies and treatment procedures concerning the management, prevention and eradication of harmful Zika virus. Hence to conclude, with the usage of the above mentioned public health strategies, along with adequate public health education, the global communicable disease threat of Zika virus can be wiped out.

References

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