Introduction
Many of the diseases, until recently considered exotic, which were mainly distributed in tropical and subtropical endemic foci of Africa and Asia, began to dramatically expand their range, capturing countries in the temperate climatic zone. In terms of the spread of West Nile fever in many countries, it is the most significant arbovirus infection in socio-economic conditions. The pathogen does not result in serious symptoms in the majority of cases, but the lack of vaccine makes combatting the disease during complications highly challenging.
Background
West Nile Fever virus was initially present in Uganda, Africa. Gradually, the population of Uganda and equatorial Africa developed an immunity to the disease, however, by this time, the virus spread to other, more distant regions (Chancey et al., 2015). Most infections are asymptomatic, but in small cases, either fever or West Nile disease develops. The main symptoms of West Nile fever are manifestations of intoxication syndrome. This includes fever, headache, fatigue and body aches, nausea, vomiting, skin rash, and lymphadenopathy. The disease has a distinct seasonality, and mosquitoes and ticks are carriers of the virus. The virus is primarily transmitted by birds of water-near-water complexes, but people and many mammals can also become infected after being bitten by an infected mosquito.
Arbovirus infections are the most numerous group among diseases of viral etiology. Arboviruses include a large group of viruses that are transmitted by a bite of blood-sucking arthropod vectors to susceptible vertebrates (Chancey et al., 2015). To date, a large number of arboviruses have been described in the world, some of them are capable of causing disease in humans, and this list is constantly growing. To date, there is no preventive or recreational therapy, as well as vaccines to protect against the virus. Therefore, preventive measures to protect against mosquito bites are recommended. Although the infection caused is considered a relatively mild disease for the general population, the severe fetal development disorders associated with it indicate the need to reduce the risk of infection, especially for women of childbearing age during pregnancy.
One can highlight the number of clinical variants of West Nile fever, such as asymptotic forms. In addition, there is a form of the disease without damage to the central nervous system, that is, acute febrile illness with general intoxication syndrome. Fever with damage to the central nervous system is serous meningitis and serous meningoencephalitis. Therefore, the fever is primarily caused by the West Nile virus, and it belongs to the genus Flavivirus of the Flaviviridae family, contains single-stranded, non-segmented RNA and its replication occurs in the cytoplasm of the affected cells (Chancey et al., 2015). The shape is similar to typical spherical viruses, and its size is approximately 50 nm. The agent is enveloped, and the components include envelope, pre-membrane, capsid, and RNA (Acharya & Bai, 2016). It is replication heavily reliant on the host’s bimolecular machinery, where it uses its original positive RNA strand and transcribes negative-sense strands to create proteins and multiply (Bai et al., 2019). West Nile Fever virus belongs to the antigenic complex of Japanese encephalitis, which also includes encephalitis pathogens, yellow fever, and dengue.
Diseases caused by the viruses of this complex are characterized by fever, hemorrhagic syndrome, central nervous system damage, hepatitis, which are found in various combinations. West Nile Fever is an acute viral, vector-borne, natural focal infection that occurs with high fever, skin rashes, and most often with severe symptoms of meningitis and meningoencephalitis (Bai et al., 2019). After entering the body, the virus spreads through the bloodstream and causes damage to the vascular endothelium, including the microvasculature, which may be accompanied by the development of thrombohemorrhagic syndrome. Viremia with West Nile fever is mostly short-lived and non-intense.
West Nile fever is clinically and pathogen-morphologically an absolute neuron-based infection. From the early stages of the disease and in the dead, the West Nile virus is detected in macrophages of the pia mater, neurons of the central nervous system, as well as in areas of cell death. The greatest tropism of the West Nile virus was detected for the regions of the hippocampus, thalamus, substantia nigra, cerebellum, brain stem, and the front horns of the spinal cord. In these sections, the expression of virus antigens was combined with the phenomena of vasculitis with perivascular accumulations of main lymphocytes and microglial elements, as well as dystrophic, necrosis related, and necrotic changes in nerve cells. The morphological manifestation of the central nervous system tissues is prone to a pronounced endothelial effect of the West Nile fever virus (Bai et al., 2019). In this regard, in the pathogenesis of this disease, it is necessary to consider the violation of the permeability of the blood-brain barrier, especially in the basal parts of the brain, to be an important mechanism.
In the world, many types of mosquitoes can be carriers of the West Nile virus, which is especially hazardous for humans. Meanwhile, only fragmentary data are available on the fauna, ecology of mosquitoes, and their role in the circulation of pathogens of especially dangerous infections in urban landscapes, including in residential areas (Chancey et al., 2015). The global emergence and re-emergence events occur due to mosquito-spread, which creates a transmission network for viral infection.
Science Articles
The main purpose of the study is to introduce Nexstrain, which is a monitoring tool for viruses. It allows specialists to track the overall evolutionary changes and novel pathogen modifications. The hypothesis is that genomics and related fields can be highly useful in monitoring West Nile virus emergence in the United States. In addition, it can help to design effective preventative measures to ensure elevated public awareness and build focused control measures (Hadfield et al., 2019). The independent variable is mosquito and bird movement patterns across the United States, whereas the dependent variable is West Nile virus infections spread.
The previous studies were conducted by basic epidemiological tools, which lack the specificity of the Nextstrain to particular strains. One needs to be aware that the virus is highly prone to changes and modifications in its genome. The given tool is an interactive visualization approach for the West Nile virus, where the strains are primarily distinguished through genomics and the corresponding differences. However, it is important to understand that the outcome of previous studies was mainly done by taking into account instances of infections and the local features. In the past epidemiologists primarily utilized the concepts, such as a molecular clock or “shoe-leather epidemiology” (Martin, 2016). In the former case, an expert needed to conduct thorough research by visiting each infected individual or reported observation. In the case of the molecular clock, the rapid replication and division among bacteria or multiplication among viruses manifest itself in massive gene difference that occurs in a short period (Martin, 2016). Therefore, an epidemiologist can estimate the length of the activity of the pathogen by observing its molecular clock.
West Nile virus datasets were used in conjunction with the viral strain analysis to build a spatial and temporal genomic database. Nextstrain was used to combine the given complex set of information, which allowed researchers to create a strain-specific map of movement and evolution across the nation (Hadfield et al., 2019). Therefore, the tool was useful to understand the movement patterns of various West Nile virus strains.
The relevance of studying the spread of arbovirus infections and influenza viruses is determined by the scale of circulation of these pathogens, their preservation in natural foci, and, of course, the danger of diseases. Global warming and anthropogenic impact on natural foci cause the expansion of the ranges of carriers, hosts, and pathogens of natural focal infectious diseases (Hadfield et al., 2019). In this regard, constant large-scale surveys of territories, and, in particular, America, are necessary. In addition, the region every year attracts an increasing number of immigrants and tourists visiting the widespread foci of arbovirus infections in the season of their maximum danger. The Nextstrain is an outstanding demonstration of West Nile spread and evolution visualization, and thus, combining genomics with temporal and spatial dataset mapping is effective at tracking the pathogen and predicting potential outbreaks (Hadfield et al., 2019). The most interesting aspect of the study is the fact that the given tool is highly specific on strain level, which allows epidemiologists to utilize unique features of each form.
The 2016 study on the possible treatment approaches for West Nile virus infections shows that monoclonal therapeutic antibodies can help create a vaccine. The vaccination can either occur on the animal level, where potentially infected species will be vaccinated. However, the primary objective is to design effective methods of treating the disease and protecting people from further infections through siRNA, antiviral compounds, therapeutic antibodies, and protective vaccines (Acharya & Bai, 2016). Therefore, there are several methodological approaches to ensuring safe and reliable West Nile virus treatment. Another 2019 study focuses on the clinical manifestations of the West Nile virus, where the lack of standard vaccine and therapy makes it challenging to combat the spread of the infection. However, the neuroinvasion mechanisms show that the virus enters the brain through blood vessels and destroys neuron cells (Bai et al., 2019). The neutrophil response might not be sufficient to eliminate the infected cells due to the pathogen’s quick replication. Therefore, the most effective measures revolve around creating protective vaccines, which would be based on natural immune memory.
Conclusion
In conclusion, the West Nile virus is a highly dangerous pathogen that spread through mosquitos and birds. Although the majority of cases do not show any symptoms, the rare instances of complications lead to meningitis and neuroinvasion. The lack of proper vaccine and therapy makes the virus treatment challenging because it is generally quick at spreading. The disease itself takes the form of fever and extreme health deterioration, which makes the pathogen deadly during complications. Nexstrain is a valid solution to the monitoring process after the spread of the virus, and it allows epidemiologists to have a real-time assessment of the movements of particular strains.
Glossary
Arbovirus – viruses that spread through arthropods, such as mosquitos, mites, and ticks.
Macrophage – a large immune cell-specialized at engulfing pathogens.
Antibody – a protein structure that has an affinity towards the pathogens’ proteins or antigens.
References
Acharya, D., & Bai, F. (2016). An overview of current approaches toward the treatment and prevention of West Nile virus infection. Methods in Molecular Biology, 1435, 249-291.’
The research focuses on the possible measures that could lead to virus treatment, such as siRNA, antiviral compounds, therapeutic antibodies, and protective vaccines.
Bai, F., Thompson, E. A., Vig, P., & Leis, A. A. (2019). Current understanding of West Nile virus clinical manifestations, immune responses, neuroinvasion, and immunotherapeutic implications. Pathogens, 8(4), 193-214.
The researchers analyze and determine the mechanisms behind neuroinvasion.
Chancey, C., Grinev, A., Volkova, E., & Rios, M. The global ecology and epidemiology of West Nile virus. Vector-Borne Viral Diseases, 2015, 1-20.
The study summarizes the West Nile virus’s features and describes the risks of new outbreaks.
Hadfield, J., Brito, A. F., Swetnam, D. M., Vogels, C. B. F., Tokarz, R. E., Andersen, K. G., Smith, R. C., Bedford, T., & Grubaugh, N. D. (2019). Twenty years of West Nile virus spread and evolution in the Americas visualized by Nextstrain. PLOS Pathogens, 15(10), 1-18.
The research focuses on the international spread of the West Nile virus and the use of Nextstrain to track the pathogen’s movement across the US on strain-level.
Martin, E. T. (2016). Genetic detectives: How scientists use DNA to track disease outbreaks. The Conversation. Web.
The article summarizes the various virus tracking approaches that were utilized across a wide range of periods.