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An Overview on the Current Literatures and Medical Diagnosis of Zika Virus

Paper Type: Free Essay Subject: Medical
Wordcount: 4483 words Published: 17th Mar 2021

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Abstract:

Zika virus is a member of the family of Flaviviridae, and its spread by Aedes mosquitoes. It has been linked to microcephaly in neonates, and it has a great risk to pregnancy in humans. Zika virus infection implicated in serve of neurological disorder and fetal microcephaly and including Guillain-Barre syndrome. There is no vaccine available to treat Zika virus infection. The antigenic similarities between Zika and dengue combined to high-level immunity and target larger population. Zika virus causes a serious condition to the nerve system and it causes a significant challenge on public health. The most recent research reviews that Zika more served in neurological complications, such as fetal microcephaly. The mosquitos and Aedes aegypti mosquitos are predominantly key transmission of Zika virus. Here, we review the most and recent literature and the status of Zika outbreak including the availability of medical countermeasure options and current diagnosis methodology.

Keywords: Zika. Dengue, Flavivirus, Mosquitos, Microcephaly, Aedes aegypti.

Introduction:

Zika virus is a member of family Flaviviridae (humans and other mammals serve a natural hosts), and it was firstly discovered in Uganda at Zika forest in 1947 [1]. It was isolated from the blood of sentinel rhesus macaques in 1948 [2]. Zika antibody firstly detected in human body in Africa and the first infection reported in 1964 [3]. It is difficult to detect Zika virus antibody, because of cross reactivity or similarity with other related Flavivirus such as dengue. This especially in those patients previously vaccinated against other Flaviviruses [4]. The first serious outbreak reported in Yap Island in 2007, and 73% of the population infected with Zika virus within the period of 4 months [5]. In 2013, there was a major outbreak in French Polynesia [6]. Since then the Zika virus introduced to the west Hemisphere and causing a large epidemic in south America, with localized epidemic in Argentina, Brazil, Venezuela, Paraguay, El Salvador, Columbia south United State and Singapore [7, 8,9,10,14]. The list of countries with high risk of Zika infections are shown in Table 1.

Table 1: Zika Virus: Countries Specific Risk

Angola

Bonaire

Cuba

French Guiana

Mexico

Grenadines

Anguilla

Brazil

Curaçao

Gabon

Nigeria

Samoa

Antigua

Cambodia

Costa Rica

Grenada

Panama

Senegal

Argentina

Cameroon

Côte D’Ivoire

Guatemala

Papua New Guinea

Saint Martin

Aruba

Cape Verde

Cuba

Guyana

Paraguay

Turks & Caicos Islands

American Samoa

Cayman Islands

Curaçao

Haiti

Philippines

Uganda

Angola

 African Republic

Dominica

Honduras

Puerto Rico

Thailand

Bahamas

Texas

Dominican Republic

India

Saba

Tonga

Bangladesh

Colombia

Ecuador

Indonesia

Saint Barthélemy

Trinidad &Tobago

Barbados

Cape Verde

El Salvador

Jamaica

Saint Kitts and Nevis

Venezuela

Belize

Costa Rica

Ethiopia

Malaysia

Saint Lucia

Vietnam

Bolivia

Côte D’Ivoire

Fiji

Maldives

Saint Martin

Virgin Islands (British)

 In recent studies, the rate of neurological defects in fetus to Zika virus from the infected mothers calculated to 7% [11]. The most disadvantage of Zika virus infection is the congenital syndrome in infants, which include a spectrum of neurological defects [12]. Recent studies suggested that Zika virus has a direct effect on neuronal tissue damage [13]. However, it is not understood why not all Zika virus infections have effect on brain abnormality during embryonic development. In Flavivirus family, there are structural similarities between Zika and dengue, therefore the epidemic region is often epidemic for other Flavivirus infection [15]. The antibody raises against one of the viruses and able to cross-react with others. Here are some clinical features between Zika, dengue and Chikungunya are shown in Table 2.

Table 2: Clinical feature: ZIKA compared to Dengue and Chikungunya [16].

Features

Zika

Dengue

Chikungunya

Fever

++

+++

+++

Rash

+++

+

++

Conjugativitis

++

-

-

Arthralgia

++

+

+++

Myalgia

+

++

+

Headache

+

++

++

Hemorrhage

-

++

-

Shock

-

+

-

It has been introduced that, the binding of human dengue antibodies with Zika virus does not neutralise the Zika virus but it enhances the Zika infection in cell clutters [17]. The Zika virus genome is a single stranded positive RNA with a single open reading from the located in two structural 5’ and 3’ untranslated regions. According to the reference [18], the genome codes to seven non-structural proteins in which they are involved in replication, assembly, and analysing the host innate responses to infection.

Figure 1: Schematic representation of Zika virus genome, 11kb Zika virus genome including the 5' and 3' untranslated region.

Zika virus infected to a scientist who has contracted the virus in the laboratory, and two other US scientists reported to have contracted Zika virus when working in Senegal in 2008 [19].

The Transmission of Zika Virus:

The transmission occurs both sylvatic and urban cycles involving a variety of Aedes species and mosquitos. Zika virus is predominantly transmitted from the bite of infected female Aedes mosquitos, or most commonly Aedes aegypti. After an infected mosquito bites a human, Zika virus spread it into the draining lymph node. It amplified and disseminate through the blood stream to a peripheral tissue and visceral organs. The first symptoms it may be develop in 3 to 12 days, but it can be shorter or longer for different patients. Most recent studies suggested that, a male to female sexual transmission is also a route of Zika virus infection, but the female to male sexual transmission is not reported [20]. Zika virus virions enter the cell through the receptor-mediated endocytosis. It is not clear weather mosquitos or other mammals serve as an amplifying reservoir. The Zika transmission through the Brest feeding not revealed but it may be another route, because milk contains a high viral load. To prevent further spread of Zika virus it is critical to understand and reveal the amplifying reservoir of Zika virus.

Figure 2: Routes of Zika Virus transmission [21].

Symptoms:

The majority of those who have been infected by Zika virus have minimal symptoms. The significant symptoms will tend to cause mild and short-lived 2-7 days illness. The suggested Zika infection signs include rash, itching, fever, headache, myalgia and lower back pain. Recent research reported that the symptoms of Zika is like dengue fever and chikungunya. Aedes mosquitos also transmit these two symptoms, both are found in the same geographical area. Zika virus infection during the women pregnancy causes conventional brain abnormalities includes microcephaly [22]. People usually do not get ill; therefore, most of them are not going to the hospital. Once this virus has affected the person is more likely to be protected from the future infections.

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Microcephaly:

The most alarming aspects in recent outbreaks is increasing in congenital malformations, including the fetal microcephaly. The neurodevelopmental disorder results in abnormally formed brain and head [25]. In most recent studies reported that Zika infection has a direct link to microcephaly, includes the detection of viral RNA. Zika attenuates growth of human neural progenitor cells. It is not clear that, what type of exposure and weather symptomatic infection possess the great risk to the fetus. In addition, the other malformations reported in fetus and new born babies with congenital Zika virus infections include brain atrophy, arthrogryposis, and fetal abnormalities.

Life Cycle:

 Zika virions enter to the cell through the receptor-mediated endocytosis. Endosomal acidification results in viral fusion with the endosomal membrane and release the viral RNA into cytoplasm. The viral RNA translated into a single polyprotein. Viral replication takes place on the altered cellular membranes and progeny viral RNA. The macromolecular changes into immature virions, elicited by changes in pH. The E protein is responsible for the virus entry through the host membrane. However, the exact mode of entry has not yet understood. The virus spreads to the lymph and blood nodes and it replicates in cytoplasm.

Diagnosis and test for Zika Virus:

Zika Virus can be detected from human blood within the first 10 days of infection in viral loads of peaking at the onset of symptoms. Zika virus requires the presence of fever with arthralgia or with arthritis, and or no purulent conjunctivitis. This requires symptoms with conjunction and the presence of anti-Zika virus IgM antibodies. The confirmation requires the laboratory test to detect the presence of Zika virus with RNA. According to reference [7] 25% of patients requires (one month) artificial ventilation, 20% of patients remains non ambulatory for at least 6 months, and 3-10% of patients dies despite the lack of standard care.

It is difficult to distinguish between people who previously infected with or vaccinated against other related Flavivirus. The early filtration that studied ZIKA virus indicated the size of ZIKA virus in the range of 30-45nm in diameter [13]. The electron transmission microscopy ETM analysis for the ZIKA infected cells reveals the virions is spherical with a range of 40-43 nm in diameter. ZIKA suspension most stable at pH 6.8-7.4. Zika particles can be inactivated at pH 6.2 and over 7.8 by potassium permanganate either temperature 58C for 30min or 60C for 15 min.

Treatment:

There is no vaccine available; however, the Zika virus infection is mild, and the standard treatment now is supporting nurse care and relief of the symptoms. For pregnant women, It is suggested that to get more rest and to drink plenty of water and manage pain and fever with paracetamol and other cooling measures. In the most cases, pregnant women should seek medical care. For the relieving symptoms, it suggested to rest with drinking plenty of water and taking medications such as acetaminophen.

Lateral flow Assay (LFA) Test for Zika virus:

The lateral flow assay tests can be used to diagnosis Zika virus. The use of lateral flow test is simple, not expensive and the test can be stored at ambient temperature. The LFA test made up with a sample pad, conjugate pad, nitrocellulose strip that contains test and control lines and a wicking pad. Each of this component must overlap by at least 1mm to enables unimpeded capillary flow of the sample. The sample pad filter unwanted particulates. The sample can flow to the conjugate pad that contain strongly coloured gold nanoparticles and have antibody on their surface. When it reaches the conjugate pad, these dried gold nanoparticles are released and mix with the sample. If the target recognised, then it will bind to the antibody. The analytic bound gold nanoparticle will flow through the nitrocellulose membrane and cross the test line and control line. The control line contains the affinity ligands that will bind with the gold nanoparticles. The conjugate with the analytic present in the solution is to confirm that the assay is working. The analytic time is depending on the type of membrane used and typically takes less than 15min.

Summary

Zika virus outbreak has been declared as a public health emergency in many countries in the past. The countries with a risk level presented in Table 2. The virus is not endemic; therefore, the risk of spreading into international regions because of air travel and trades are more likely. The locations with mosquitos vectors are easy for the virus transmission. The Zika virus vectors, epidemiology and pathology remain uncertain. The diagnosis remains less than standard, and the laboratory diagnostics are not widely available. The commercial test of Zika virus is limited. This includes molecular assays and Lateral flow tests. In some cases, the similar assay test of CHIKV, and DENV are used for testing Zika which is not unique to Zika virus test, and it has a lack of capability in detecting the virus. According to the World Health Organisation (WHO) the prevention measures of vector control is a current priority. Nerveless the cheap and fast, reliable, lateral flow test requires for Zika virus diagnosis. The morphological aspects of Zika virus remains unclear. Zika virus has a natural tendency or inclination to infect large number of people in the same region. The epidemic has a major economic, medical, ethical problem in countries of the early resource diagnosis. The Zika virus transmission from the mother to fetus during the pregnancy period is a major issue. The Zika transmission through the brest feeding not revealed but it may be another route, because milk contains a high viral load. According to the recent literature, 4 out of 5 peoples who infected with Zika virus have no sign of symptoms. The symptoms usually occur during 7 days after being bitten by the mosquitos. There is no vaccine exist for Zika virus treatment. The suggested treatments are taking a rest, drink plenty of water and take medications such as acetaminophen. In the current review, we have covered the most recent publications regarding the Zika outbreak and biological analysis for Zika virus. There has no unique testing for early diagnosis of Zika virus. The current diagnosis methods are taking long time and they are not available worldwide. The need of cheap, fast, and reliable testing method such as lateral flow testing requires for Zika virus diagnosis. This review can help, and advantage our knowledge, and provides the information for understanding the recent outbreak and related researches to Zika virus.

References

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