Zika virus ( ZIKV ) is a member of the virus family Flaviviridae . It is propagated by daytime active Aedes mosquitoes, such as A. aegypti and A. albopictus . Its name comes from the Uganda Ziika Forest, where it was first isolated in 1947. The Zika virus is linked to dengue fever, yellow fever, Japanese encephalitis, and West Nile virus. Since the 1950s, it has been known to occur in the narrow equatorial belt from Africa to Asia. From 2007 to 2016, the virus spreads to the east, across the Pacific Ocean to America, leading to the Zika 2015-16 virus epidemic.
The infection, known as Zika fever or Zika virus disease, often causes no or only mild symptoms, similar to a very mild dengue fever. Although there is no specific treatment, paracetamol (acetaminophen) and rest can help with symptoms. By 2016, the disease can not be prevented with drugs or vaccines. Zika can spread from a pregnant woman to her baby. This can lead to microcephaly, severe brain malformations, and other birth defects. Zica infections in adults can cause uncommon in Guillain-Barrà ©  © syndrome.
In January 2016, the United States Centers for Disease Control and Prevention (CDC) issued travel guidance to affected countries, including the use of enhanced preventive measures, and guidelines for pregnant women including considering travel delays. Government or other health agencies also issue similar travel alerts, while Colombia, Dominican Republic, Puerto Rico, Ecuador, El Salvador and Jamaica advise women to delay pregnancy until more is known about the risks. Zika is pronounced or .
Video Zika virus
Virology
The Zika virus belongs to the family Flaviviridae family and genus Flavivirus , thus linked to dengue fever, yellow fever, Japanese encephalitis, and West Nile virus. Like other flavivirus viruses, the Zika virus is enveloped and icosahedral and has a positive RNA genome, no single-stranded, 10-kilobase, and positive. It is closely related to the Spondweni virus and is one of two known viruses in the Spondweni virus clone.
Positive RNA genome can be directly translated into viral proteins. As with other flaviviruses, such as the same-sized West Nile virus, the RNA genome encodes seven nonstructural proteins and three structural proteins. One of the structural proteins encapsulates the virus. This protein is a flavivirus envelope glycoprotein, which binds the host cell's endosome membrane to initiate endocytosis. The RNA genome forms the nucleocapsid along with copies of 12-kDa capsid protein. The nucleocapsid, in turn, is enveloped in a host-derived membrane modified with two viral glycoproteins. Virus genome replication depends on the manufacture of double-stranded RNA from a single genome, positive rNA (ssRNA ()) followed by transcription and replication to provide viral mRNA and the new ssRNA () genome.
A longitudinal study showed that 6 hours after the cells were infected with the Zika virus, the vacuoles and mitochondria in the cells began to swell. This swelling becomes very severe, resulting in cell death, also known as paraptosis. This form of programmed cell death requires gene expression. IFITM3 is a trans-membrane protein in cells that can protect it from viral infections by blocking virus attachments. The cells are most susceptible to Zika infections when the IFITM3 level is low. Once the cells have been infected, the virus restructures the endoplasmic reticulum, forming a large vacuole, resulting in cell death.
There are two lineages of Zika: African lineage and Asian lineage. Phylogenetic studies show that the spread of the virus in America is 89% identical to the genotype of Africa, but most closely related to the Asian strains circulating in French Polynesia during the outbreak of 2013-2014.
Asian tensions seem to have evolved around 1939.
Maps Zika virus
Transmission
The host of virus vertebrates are mainly monkeys in the so-called enzootic mosquito-mosquito cycle, with only occasional transmission to humans. Before the current pandemic began in 2007, Zika "rarely causes known 'abundant' infections in humans, even in highly enzootic areas." Rarely, however, other arboviruses have become human diseases and spread in the cycles of mosquito-human mosquitoes, such as yellow fever virus and dengue virus (both flaviviruses), and chikungunya virus (toga virus). Although the reasons for the pandemic are unknown, dengue, associated arboviruses that infect the same species of mosquito vector, are known especially for intensification by urbanization and globalization. Zika is mainly spread by the Aedes aegypti mosquitoes, and can also be transmitted through sexual contact or blood transfusions. The basic reproduction number ( R 0 , size of transmissibility) of the Zika virus has been estimated between 1.4 and 6.6.
In 2015, news reports drew attention to Zika's rapid spread in Latin America and the Caribbean. At that time, the Pan American Health Organization published a list of countries and territories that experienced "local Zika virus transmission" comprising Barbados, Bolivia, Brazil, Colombia, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti , Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, and Venezuela. As of August 2016, more than 50 countries have experienced active (local) Zika virus transmissions.
Mosquito
Zika is mainly spread by the female mosquito Aedes aegypti , which is mostly active during the day. Mosquitoes have to eat blood to lay their eggs. The virus has also been isolated from a number of species of arboreal mosquitoes within the genus Aedes, such as A. africanus, A. apoccargusus A. furcifer , A. hensilli , A. luteocephalus , and A. vittatus , with an extrinsic incubation period of 10 days in the mosquito.
The actual extent of the vector is still unknown. Zika has been detected in more species of Aedes, along with Anopheles coustani, Mansonia uniformis , and Culex perfuscus , although this alone does not incriminate them as vectors.
Transmission by A. albopictus , a tiger mosquito, was reported from a 2007 urban pandemic in Gabon, where it has just invaded the country and became a major vector for the chikungunya virus outbreak and dengue fever. New outbreaks can occur if someone carrying the virus travels to another region where A. albopictus is common.
Zika's social risk potential can be limited by the distribution of mosquito species that transmit it. The global distribution of the most frequently quoted Zika carrier, aegypti , is growing due to global trade and travel. A. aegypti is now the most widely distributed ever recorded - across the continent including North America and even the European suburbs (Madeira, The Netherlands, and the northeastern Black Sea coast). The population of mosquitoes capable of carrying Zika has been found in a Capitol Hill neighborhood in Washington, DC, and genetic evidence suggests they survive at least four consecutive winters in the region. The study authors concluded that mosquitoes adapt to persistence in the northern climate. The Zika virus appears to be transmitted through mosquitoes for about a week after infection. The virus is considered infectious for a longer period after infection (at least 2 weeks) when transmitted through semen.
Research into the ecological niche shows that Zika can be affected to a greater extent by changes in precipitation and temperature than dengue, making it more likely to be confined to the tropics. However, the increase in global temperatures will allow disease vectors to expand their range further north, allowing Zika to follow.
Sexual
Zika can be transmitted from men and women to their sexual partners; the most known cases involve transmission from symptomatic men to women. In April 2016, Zika's sexual transmission has been documented in six countries - Argentina, Chile, France, Italy, New Zealand and the United States - during the 2015 outbreak.
Since October 2016, the CDC has advised men who have traveled to an area with Zika having to use condoms or not having sex for at least six months after they return because the virus can still be contagious even if symptoms never develop.
Pregnancy
Zika virus can spread through vertical transmission (or "mother-to-child"), during pregnancy or during childbirth.
Blood Transfusion
Until April 2016, two cases of Zika transmission through blood transfusions have been reported globally, both from Brazil, after which the US Food and Drug Administration (FDA) recommended blood donor screening and delayed high-risk donors for 4 weeks. A potential risk has been suspected based on a blood donor screening study during the French Zika Polynesian outbreak, where 2.8% (42) donors from November 2013 and February 2014 were confirmed positive for Zika RNA and all asymptomatic at the time of blood donation. Eleven positive donors reported symptoms of Zika fever after their donation, but only three of the 34 samples grew in culture.
Pathogenesis
The Zika virus replicates in the epithelial cells of the mosquito's midgut and then the salivary gland cells. After 5-10 days, the virus can be found in mosquito saliva. If the mosquito saliva is inoculated into human skin, the virus can infect epidermal keratinocytes, skin fibroblasts and Langerhans cells. Viral pathogenesis is hypothesized to continue spreading to lymph nodes and bloodstream. Flaviviruses replicate in the cytoplasm, but the Zika antigen has been found in the nucleus of the infected cell.
Zika fever
Zika fever (also known as Zika virus disease) is a disease caused by the Zika virus. Most cases have no symptoms, but when present it is usually mild and can resemble dengue fever. Symptoms may include fever, red eyes, joint pain, headache, and maculopapular rash. Symptoms generally last less than seven days. It does not cause reported deaths during initial infection. Infection during pregnancy causes microcephaly and other brain malformations in some infants. Adult infection has been associated with Guillain-Barrà ©  © (GBS) syndrome.
The diagnosis is by testing the blood, urine, or saliva for the presence of Zika virus RNA when the person is sick.
Prevention involves the reduction of mosquito bites in the area where the disease occurs, and the proper use of condoms. Efforts to prevent bites include the use of mosquito coils, which cover most of the body with clothes, mosquito nets, and get rid of puddles where mosquitoes reproduce mosquitoes. There is no vaccine. Health officials recommend that women in areas affected by the Zika 2015-16 outbreak consider delaying pregnancy and that pregnant women do not travel to this area. Although no specific treatment, paracetamol (acetaminophen) and rest can help to overcome the symptoms. Admission to the hospital is rarely needed.
Vaccine development
The World Health Organization has suggested that priority should be to develop inactivated vaccines and other nonlive vaccines, which are safe for use in pregnant women.
In March 2016, 18 companies and institutions were developing vaccines against Zika, but they claimed the vaccine would not be widely available for about 10 years.
In June 2016, the FDA granted the first approval for human clinical trials for the Zika vaccine. In March 2017, the DNA vaccine was approved for phase 2 clinical trials. The vaccine consists of a small piece of circular DNA, known as a plasmid, which expresses genes for the Zika virus envelope protein. Since the vaccine does not contain a complete range of viruses, it can not cause infection. Until April 2017, subunit and inactivation vaccines have entered clinical trials.
History
Isolation of virus in monkeys and mosquitoes, 1947
The virus was first isolated in April 1947 from a rhesus monkey placed in a stable in the Ziika Forest of Uganda, near Lake Victoria, by scientists from the Yellow Fever Research Institute. The second isolation of the mosquito africanus followed on the same site in January 1948. When the monkey had a fever, the researchers isolated from its serum as a "transmissable filterable agent" named Zika in 1948.
First evidence of human infection, 1952
Zika was first known to infect humans from the results of a serology survey in Uganda, published in 1952. Of 99 tested human serum, 6.1% had antibody antidote. As part of a yellow jaundice investigation in 1954 suspected of yellow fever, the researchers reported the isolation of the virus from a patient, but the pathogen was later proven to be a closely related Spondweni virus. Spondweni was also determined to be the cause of self-inflicted infection in a researcher reported in 1956.
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Further serological studies in several African and Asian countries indicate that the virus has spread widely in the human population of the region. The first true case of human infection was identified by Simpson in 1964, who himself was infected while isolating the virus from mosquitoes. From then until 2007, there were only 13 confirmed cases of human Zika infection from Africa and Southeast Asia. A study published in 2017 shows that the Zika virus, although only a few cases have been reported, has been secretly circulating in West Africa over the past two decades when blood samples collected between 1992 and 2016 were tested for IgM ZIKV antibodies.
Micronesia, 2007
In April 2007, the first outbreaks outside Africa and Asia occurred on the island of Yap in Federated States of Micronesia, characterized by rash, conjunctivitis, and arthralgia, originally thought to be dengue, chikungunya, or Ross River disease. Serum samples from patients in the acute phase of the disease contained ZNA RNA. There were 49 confirmed cases, 59 unconfirmed cases, no hospitalization, and no deaths.
2013-2014
After October 2013, the first outbreak of Oceania showed about 11% of the population infected with French Polynesia also suffering from Guillain-Barre syndrome (GBS). The ZIKV deployment continues to New Caledonia, Easter Island, and the Cook Islands and where 1385 cases are confirmed in January 2014. During the same year, Easter Island recognized 51 cases. Australia began looking at cases in 2012. Research shows that it was brought by returning travelers from Indonesia and other infected countries. New Zealand also experienced increased rates of infection through returning foreign tourists. Oceania's current Zica countries are New Caledonia, Vanuatu, Solomon Islands, Marshall Islands, American Samoa, Samoa, and Tonga.
Between 2013 and 2014, further epidemics occurred in French Polynesia, Easter Island, Cook Islands and New Caledonia.
America, 2015-present
There are epidemics in 2015 and 2016 in America. The outbreak began in April 2015 in Brazil, and spread to other countries in South America, Central America, North America, and the Caribbean. In January 2016, the WHO said the virus was likely to spread to most Americans by the end of the year; and in February 2016, the WHO declared a group of cases of microcephaly and Guillain-Barrà ©  © syndrome reported in Brazil - allegedly linked to the outbreak of the International Emergency Public Health Emergency Zika. An estimated 1.5 million people are infected by Zika in Brazil, with over 3,500 cases of microcephaly reported between October 2015 and January 2016.
A number of countries issued travel warnings, and the outbreak is expected to have a significant impact on the tourism industry. Some countries have taken the unusual step of advising their citizens to delay pregnancy until more is known about the virus and its impact on fetal development. With the 2016 Summer Olympics being held in Rio de Janeiro, health officials around the world voiced concern over the potential crisis, both in Brazil and when international athletes and tourists return home and are likely to spread the virus. Some researchers speculate that only one or two travelers may be infected over a three-week period, or about 3.2 infections per 100,000 tourists. In November 2016, the World Health Organization stated that the Zika virus is no longer a global emergency while noting that the virus still represents "a very significant and long-term problem".
Until August 2017, the number of new Zika virus cases in America has dropped dramatically.
The testing market is not expected to stop anytime soon. Among the major areas of global markets, Latin America is expected to lead with revenues of more than US $ 2,400 by the end of 2017. The Caribbean region is expected to project the highest growth rates of the Zika virus testing market during the 2017 -2020 forecast period.
Other cases
On March 22, 2016, Reuters reported that Zika was isolated from a blood sample 2014 from an elderly man in Chittagong in Bangladesh as part of a retrospective study. Zika also occurs in Tanzania in 2015/2016.
Between August 2016 and November 2016 455 cases of Zika virus infection confirmed in Singapore.
In 2017, Angola reported two cases of Zika fever.
References
This article incorporates public domain material from websites or documents from the Centers for Disease Control and Prevention.
External links
- Zika virus - Centers for Disease Control and Prevention
- World Health Organization Zika Fact Sheet Virus
- Zika virus illustrations, 3D models, and animations
- ViralZone: Zika virus (strain Mr. 766)
- Schmaljohn, Alan L.; McClain, David (1996). "54. Alphaviruses (Togaviridae) and Flaviviruses (Flaviviridae)". In Baron, Samuel. Medical Microbiology (4th ed.). ISBN: 0-9631172-1-1. NBK7633.
- Animation on Zika from Unlimited Scientific Animation and World Health Organization (WHO)
- Virus Zika: Everything you need to know by WeMaLife (March 7, 2018)
Source of the article : Wikipedia
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