This study analyzes the relationship between the potential presence of Zika virus disease in colder geographic regions due to changes in global ecological aspects (e.g., temperature, rainfall seasons, and mosquito seasons) and its impacts on spreading Zika virus disease. For this purpose, this research conducts a content analysis of current literatures and data sets to indicate why implementing prevention strategies regarding Zika virus disease are crucial to minimize the global public health impacts of Zika virus disease in the future.
This paper is divided into the following sections:
- Introductory section to explain the problem statement and potential threats of Zika virus disease.
- Reviewing current literature and data sets to indicate presence and risk of Zika virus and its vectors in colder regions of the world due to global warming ecological impacts, travelling, transportation, and proper prevention strategies to reduce the potential risk of Zika virus disease pandemics.
- Content analysis of qualitative data like current literatures and data sets identifies potential future global threat of Zika virus disease due to global warming, changes in rainfall seasons, expansion of its vector, applicable prevention methods, constraints and opportunities to minimize Zika virus disease impacts on global public health. Moreover, to demonstrate the effect of these aspects on the public health preparedness.
- Explaining findings based on content analysis and recommending executable solutions for current and future potential danger of Zika virus disease as a public health climate change adaptation strategy. These findings and recommendation would help policy makers to plan against potential impacts to public health due to spread of Zika virus.
The temperature is increasing in colder regions of the earth and rainfall patterns are changing due to global warming (Asad & Carpenter, 2018). These factors have amplified the chance of the presence of some species of vectors (e.g., Mosquitoes) in colder regions (Carlson, Dougherty & Getz, 2016; Dhimal, Ahrens, & Kuch, 2015). Mosquitoes can spread some diseases in colder regions which are prevalent in warmer regions of the earth and raise the possibility of pandemics in different geographic regions (Brisbois & Ali, 2010). Some mosquito borne diseases (e.g., Zika, Chikungunya, and Dengue) have common vectors like Aedes aegypti and Aedes Albopictus (Asad & Carpenter, 2018; LaDeau, Leisnham, Biehler, Bodner, 2013). Zika virus disease has been at the center of attention of researchers in the past two years due to the official announcement of the World Health Organization (WHO) in 2016 for Zika virus pandemic (Ryans et al., 2017). Zika virus disease has been seen in some regions (e.g., Northern America) which was not expected (Centers for Disease Control and Prevention [CDC], 2018).
The appearance of Zika virus disease and sudden dissemination of it in Northern America raised concerns about the arrival of this disease in new geographic regions due to favorite ecological changes for Aedes (e.g., aegypti and albopictus) mosquitoes (Carlson et al, 2016; Lafferty & Mordecai, 2016). One of the main reasons of mosquitoes’ favorite environmental changes is global warming (Kilpatrick & Randolph, 2012; Kulkarni et al., 2015; Lafferty & Mordecai, 2016). This paper studies the relationships between climate change and potential appearance of Zika virus disease in colder climates to answer why implementing prevention strategies regarding Zika virus disease are crucial to minimize the global public health impacts of Zika virus disease in the future?
Appearance of vector-borne disease in new geographic regions depends on various reasons (Escobar et al., 2016; Kilpatrick & Randolph, 2012). These reasons include presence of new microorganisms (e.g., Zika virus) and species of vectors (e.g., mosquitoes) due to human activities (e.g., travel and transportation) and changes in ecological systems (e.g., increasing temperature and rainfall frequency) (Dhimal et al., 2015; Kulkarni et al., 2015; LaDeau et al., 2013; Thomas, Tjaden, Van den Bos, & Beierkuhnlein, 2014). These elements can provide suitable conditions for reproduction of new microorganisms and insects species (Thomas et al., 2014; Medlock & Leach, 2015). The ecological suitable conditions will facilitate the transmission of these new types of diseases and threat the public health around the world (Escobar et al., 2016; Mills, Gage, & Khan, 2010; Negev et al., 2015). According to WHO (2018), 80% of peoples globally are exposed to at least one vector-borne disease (Figure. 1).
Arrival of new vector-borne diseases (e.g., Zika virus, Chikungunya, and Dengue) by a common mosquito species (e.g., Aedes aegypti and Aedes albopictus) in new geographic regions has increased the global concerns about new pandemics around the globe (Carlson et al., 2016; Dhimal et al., 2015; Medlock & leach, 2015).
One of the vector-borne diseases which can menace the public health around the world is Zika virus disease which was known for the first time “in 1947 in monkeys in Uganda” (CDC, 2018, European Center for Disease Prevention and Control [ECDPC], 2018; WHO, 2018). Zika virus can cause “neurologic” problems for everyone (e.g., “Guillain-Barre syndrome”) and genetic deformity in newborns (e.g., “Microcephaly”) (Carlson et al., 2016; WHO, 2018). This vector-borne disease has other transmission pathways than mosquito bites like sexual contact, organ transplantation, transferring blood and blood products, and mother to embryo (Asad & Carpenter, 2018; Butanis, 2017; WHO, 2018; CDC, 2018). Currently, there is not any remedy or vaccine for the Zika virus disease and its syndrome; it can only recognized by medical exams on body fluids (CDC, 2018; WHO, 2018). In other words, controlling the major transmission pathways (e.g., mosquitoes’ population) and applying prevention strategies are some solutions which can minimize the public health impacts of Zika virus disease (CDD, 2018; ECDPC, 2018; WHO, 2018).
It has been estimated that longer rainfall seasons, increasing global temperature by 2C⁰ till the end of this century, and sea level rise can elongate the mosquito seasons and population growth even in colder and high-altitude areas (Dhimal et al., 2015; Wu, Tian, Zhou, Chen, & Xu, 2013; Ramasamy & Surendran, 2011). Aside from longer mosquitos’ seasons, tourism and conveying cargos can induce transmission of mosquito borne-diseases such as Zika (Munos, Thompson, Goddard, & Aldighieri, 2016; Thomas et al., 2014). Scholars have recommended to control the population of mosquitoes (e.g., eliminating the suitable conditions for mosquito’s reproduction), conducting proactive surveillance (e.g., supervising raise of numbers of morbidity and symptoms), implementing stricter public regulations regarding global transportation (e.g., travel alerts and restrictions during the outbreaks), and applying climate change adaptation strategies to reduce the potential threats of mosquito borne-diseases like Zika (Thomson, Muñoz, Cousin, & Shumake-Guillemot, 2018; Thomas et al., 2014; Ramasamy & Surendran, 2011; WHO, 2018; ECDPC, 2018).
According to WHO (2018), Zika virus disease has been seen in “86” countries and it has potential to be seen in new countries due to future suitable ecological conditions for Aedes aegypti mosquito. Some studies indicate that presence of this mosquito species above 6,500 feet and threat of Zika virus disease is very low (CDC, 2018). There are “186” reported Dengue fever diseases in altitude above 6,500 feet (e.g., Nepal) due to presence of Aedes aegypti (Dhimal et al., 2015, p. 3). Moreover, there are other reported mosquito borne-diseases (e.g., Chikungunya) in countries with colder weathers (e.g., Canada and UK) which could confirm the presence of Aedes aegypti and Aedes Albopictus mosquitoes (Kulkarni et al., 2015; Medlock & Leach, 2015).
Aedes albopictus can tolerate colder weather than Aedes aegypti and will be able to expand its territory faster due to future global warming (Medlock & Leach, 2015). The eggs of these mosquitoes will remain safe in frozen water and convert to larvae during the suitable temperature (10 C⁰) and turn into an adult mosquito when the weather become warmer (16 C⁰-36 C⁰) (Marinho et al., 2016). Although, the chance of Zika virus outbreaks is low in countries with cold weather and altitude more than 2,500 feet but presence and expansion of its vectors would augment the potential of an outbreak in these parts of the world (Asad & Carpenter, 2018; ECDPC, 2018; Kulkarni et al., 2015; Medlock & Leach, 2015; Thomas et al., 2014; Wu et al., 2013). It can be said, countries with colder weather and higher altitudes need to consider prevention strategies to enhance their public health preparedness, otherwise they would not be able to respond to potential outbreaks of Zika virus disease.
More frequent torrential rainfalls, changes in rainfall seasons, increasing temperature and sea level due to climate change will provide suitable conditions for reproduction of mosquitoes (LaDeau et al., 2013; Negev et al., 2015; Ramasamy & Surendran, 2011; Ryan et al. 2017; Thompson et al., 2018). Mosquitoes put their eggs in standing water (e.g., puddles and water containers) and their larvae can grow up in these environments (Ramasamy & Surendran, 2011; WHO, 2018). There are evidences that mosquitoes can also breed in standing salt water, which is the result of accumulation of salt water in the coast line puddles due to increasing sea level (Ramasamy & Surendran, 2011). There is a linear relationship between longer rainfall seasons with higher temperature and Zika virus disease outbreaks due to reproduction of more Aedes (e.g., aegypti and albopictus) mosquitoes in different geographic regions (Asad & Carpenter, 2018; Carlson et al., 2016; Dhimal et al., 2015; Lafferty & Mordecai, 2016; Thompson et al., 2018). In addition, the concentration of mosquito’s population in the vicinity of residential areas and the inability to implement prevention strategies due to poverty will accelerate the transmission of Zika virus (LaDeau et al, 2013; Kilpatrick & Randolph, 2012). Controlling mosquito’s population to prevent Zika virus disease transmission and enhance public health preparedness depends on various factors such as the relationship between environmental (e.g., standing waters and water containers) and socioeconomic aspects (e.g., poverty and land use) (LaDeau et al., 2013; Ryan et al., 2017). In other words, socioeconomic and climate change impacts on the environment are intertwined and without considering these factors, implementing public health preparedness strategies is in vain.
Tourism and transportation would increase the expansion of Zika virus in non-endemic countries (Dhimal et al., 2015; Medlock & Leach, 2015; Thomas et al., 2014). Travelling to and from countries in tropical and warm regions may put people in peril of Zika virus disease and sick people would spread Zika virus through sexual activities, mother to unborn babies, transferring blood products, and mosquitos’ bites (Dhimal et al., 2015; Kilpatrick & Randolph, 2012; Kulkarni et al., 2015; Negev et al., 2015; ECDPC, 2018). Zika vectors (e.g., Aedes aegypti and Aedes albopictus) can also travel to other countries (e.g., auto tires and plants) and be reason of Zika virus spread (Medlock & Leach, 2015; Thomas et al., 2014). These mosquitoes could be introduced and breed in new regions due to suitable ecological conditions (e.g., long rainfall seasons and increasing temperature), and also can make Zika virus an endemic microorganism in new areas (Carlson et al., 2016; Medlock & Leach, 2015; Thomas et al., 2014; Thompson et al., 2018; Wu et al., 2013, WHO, 2018). Presence of new microorganisms and mosquitoes will put public health in danger due to lack of preparedness for these new threats.
Increasing global temperature and frequency of rainfalls have changed the mosquito season’s pattern around the world and made the environment more suitable for spreading Zika virus disease. Travelling and carriage of cargo could disseminate Zika virus and its main vectors in new geographic areas. Suitable reproduction conditions for mosquitoes due to climate change and the presence of Zika virus would ignite another global pandemic in regions that are not well prepared for appearance of Zika virus disease. Zika virus disease can cause serious health issues for current and future generations.
Although there is not a remedy for Zika virus disease but implementing prevention methods as a part of climate change adaptation activities would reduce the impacts of this disease and prevent another global pandemic. Decelerating the negative ecological influences Zika virus disease relies on global collaboration and it is a long-term goal. It is exigent to apply a practical solution for current Zika virus threats to reduce the number of morbidities among current and future populations. It seems that controlling mosquitoes’ population and enhancing public health preparedness like proactive surveillance of symptoms, blood test results, mosquitoes’ species, and current reported Zika diseases would be practical solutions due to climate change. Furthermore, promoting public awareness regarding Zika disease preventive methods (e.g., using insect repellant and travel alerts), transmission pathways (e.g., sexual, body fluids, and mother to baby), and its illness signs can minimize spreading Zika virus diseases.