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Senin, 01 Februari 2016

BELAJAR TENTANG VIRUS FLAVIVIRIDAE (GENUS FLAVIVIRUS) DALAM VIRUS ZIKA

Berikut merupakan kutipan ilmiah kesehatan lingkungan yang bermanfaat sehingga disusun dan digunakan sebagai referensi pribadi.


Perpustakaan keluarga : Helmut Todo Tua Simamora dan dr. Olga Y.V Hutapea




Fears over the Zika virus have intensified after El Salvador warned women not to get pregnant for the next two years, as the mosquito-borne virus could cause birth defects among newborns.
The virus is thought to cause severe brain damage in new-born babies and may also be behind rising instances of a separate potentially fatal illness that can leave patients paralysed, doctors say.

It is already suspected of being responsible for a dramatic increase in cases of microcephaly, where babies are born with abnormally small heads, in Latin America.

Zika virus (ZIKV) is a member of the Flaviviridae virus family and the Flavivirus genus.
In humans, it causes a mild illness known as Zika fever, Zika, or Zika disease, which since the 1950s has been known to occur within a narrow equatorial belt from Africa to Asia. In 2014, the virus spread eastward across the Pacific Ocean to French Polynesia, then to Easter Island and in 2015 to Central America, the Caribbean, and South America, where the Zika outbreak has reached pandemic levels.[1] Zika virus is related to dengueyellow feverJapanese encephalitis, and West Nile viruses, all of which are arthropod-borne flaviviruses.[2] The illness it causes is similar to a mild form of dengue fever,[2] is treated by rest,[3] and cannot be prevented by drugs or vaccines.[3] There is a possible link between Zika fever and microcephaly in newborn babies of infected mothers.[4][5][6] In January 2016, the U.S. Centers for Disease Control and Prevention (CDC) issued travel guidance on affected countries, including the use of enhanced precautions and considering postponing travel, and guidelines for pregnant women.[7][8] Other governments or health agencies soon issued similar travel warnings,[9][10][11] whileColombiaEcuadorEl Salvador, and Jamaica advised women to postpone getting pregnant until more is known about the risks.[10][12]
Along with other viruses in this family, Zika virus is enveloped and icosahedral with a nonsegmented, single-stranded, positive-sense RNA genome. It is most closely related to the Spondweni virus and is one of the two viruses in the Spondweni virus clade.[13][14]
The virus was first isolated in 1947 from a rhesus macaque in the Zika Forest of Uganda and in 1968 was isolated for the first time from humans in Nigeria.[15] From 1951 through 1981, evidence of human infection was reported from other African countries such as the Central African RepublicEgyptGabonSierra Leone,Tanzania, and Uganda, as well as in parts of Asia including IndiaIndonesiaMalaysia, the PhilippinesThailand, and Vietnam.[15]
The pathogenesis of the virus is hypothesized to start with an infection of dendritic cells near the site of inoculation, followed by a spread to lymph nodes and the bloodstream.[13] Flaviviruses generally replicate in the cytoplasm, but Zika virus antigens have been found in infected cell nuclei.[16]
There are two lineages of Zika virus, the African lineage and the Asian lineage.[17] Phylogenetic studies indicate that the virus spreading in the Americas is most closely related to French Polynesian strains.[17] Complete genome sequences of Zika viruses have been published.[18] Recent preliminary findings from sequences in the public domain uncovered a possible change in nonstructural protein 1 codon usage that may increase the viral replication rate in humans.[19]
Zika virus is transmitted by daytime-active mosquitoes and has been isolated from a number of species in the genus Aedes, such as A. aegypti, and arborealmosquitoes such as A. africanusA. apicoargenteusA. furciferA. hensilliA. luteocephalus, and A. vitattus. Studies show that the extrinsic incubation period in mosquitoes is about 10 days.[15] The vertebrate hosts of the virus are primarily monkeys and humans. Before the current pandemic, which began in 2007, Zika virus "rarely caused recognized 'spillover' infections in humans, even in highly enzootic areas".[20]
Aedes aegypti predicted distribution
Global Aedes aegypti predicted distribution. The map depicts the probability of occurrence (blue=none, red=highest occurrence).
The potential societal risk of Zika virus can be delimited by the distribution of the mosquito species that transmit it (itsvectors). The global distribution of the most cited carrier of Zika virus, A. aegypti, is expanding due to global trade and travel.[21] A. aegypti distribution is now the most extensive ever recorded – across all continents including North America and even the European periphery.[22]
Recent news reports have drawn attention to the spread of Zika in Latin America and the Caribbean.[23] The countries and territories that have been identified by the Pan American Health Organisation (PAHO) as having experienced "local Zika virus transmission" are Barbados, Bolivia, Brazil, Colombia, the Dominican Republic, Ecuador, El Salvador, French Guiana, Guatemala, Guadeloupe, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, and Venezuela.[24][25]
In 2009 Brian Foy, a biologist from the Arthropod-borne and Infectious Diseases Laboratory at Colorado State Universitysexually transmitted Zika virus to his wife. He visited Senegal to study mosquitoes and was bitten on a number of occasions. A few days after returning to the United States, he fell ill with Zika, but not before having had unprotected intercourse with his wife. She subsequently showed symptoms of Zika infection with extreme sensitivity to light. Foy is the first person known to have passed on an insect-borne virus to another human by sexual contact.[26][27]
In 2015, Zika virus RNA was detected in the amniotic fluid of two fetuses, indicating that it had crossed the placenta and could cause fetal infection.[28] On 20 January 2016, scientists from the state of Paraná, Brazil, detected genetic material of Zika virus in the placenta of a woman who had undergone an abortion due to the fetus's microcephaly, which confirmed that the virus is able to pass the placenta.[29]
Common symptoms of infection with the virus include mild headaches, maculopapular rash, fever, malaise, pink eye, and joint pains. The first well-documented case of Zika virus was described in 1964; it began with a mild headache, and progressed to a maculopapular rash, fever, and back pain. Within two days, the rash started fading, and within three days, the fever resolved and only the rash remained. Thus far, Zika fever has been a relatively mild disease of limited scope, with only one in five persons developing symptoms, with no fatalities, but its true potential as a viral agent of disease is unknown.[15]
As of 2016, no vaccine or preventive drug is available. Symptoms can be treated with paracetamol (acetaminophen), while aspirinand other nonsteroidal anti-inflammatory drugs should be used only when dengue has been ruled out to reduce the risk of bleeding.[30]
In a French Polynesian epidemic, 73 cases of Guillain–Barré syndrome and other neurologic conditions occurred in a population of 270,000, which may be complications of Zika virus.[20] In December 2015, the European Centre for Disease Prevention and Control issued a comprehensive update on the possible association of Zika virus with congenital microcephaly and this syndrome.[31]
Data suggests that newborn babies of mothers who had a Zika virus infection during the first trimester of pregnancy are at an increased risk of microcephaly.[32] In December 2015 it was suspected that a transplacental infection of the foetus may lead to microcephaly and brain damage.[33][34] The Brazilian Ministry of Health has since confirmed the relation between the Zika virus and microcephaly.[4]
In 1947 scientists researching yellow fever placed a rhesus macaque in a cage in the Zika Forest (zika meaning "overgrown" in the Luganda language), near theEast African Virus Research Institute in Entebbe, Uganda. The monkey developed a fever, and researchers isolated from its serum a transmissible agent that was first described as Zika virus in 1952.[35] It was subsequently isolated from a human in Nigeria in 1954. From its discovery until 2007, confirmed cases of Zika virus infection from Africa and Southeast Asia were rare.[36]
In April 2007, the first outbreak outside of Africa and Asia occurred on the island of Yap in the Federated States of Micronesia, characterized by rash, conjunctivitis, and arthralgia, which was initially thought to be dengue, Chikungunya, or Ross River disease.[37] However, serum samples from patients in the acute phase of illness contained RNA of Zika virus. There were 49 confirmed cases, 59 unconfirmed cases, no hospitalizations, and no deaths.[38] More recently, epidemics have occurred in Polynesia, Easter Island, the Cook Islands, and New Caledonia.[36]
Since April 2015, a large, ongoing outbreak of Zika virus that began in Brazil has spread to much of South and Central America, and the Caribbean. In January 2016, the CDC issued a level 2 travel alert for people traveling to regions and certain countries where Zika virus transmission is ongoing.[39] The agency also suggested that women thinking about becoming pregnant should consult with their physicians before traveling.[40] Governments or health agencies of the United Kingdom,[9] Ireland,[10] New Zealand,[41] Canada,[11] and the European Union[11] soon issued similar travel warnings. In ColombiaMinister of Health and Social Protection Alejandro Gaviria Uribe recommended to avoid pregnancy for eight months, while the countries of EcuadorEl Salvador, and Jamaica have issued similar warnings.[10][12]
Plans were announced by the authorities in Rio de Janeiro, Brazil, to try to prevent the spread of the Zika virus during the 2016 Summer Olympic Games in that city.[11]
According to the CDC, Brazilian health authorities reported more than 3,500 microcephaly cases between October 2015 and January 2016. Some of the affected infants have had a severe type of microcephaly and some have died. The full spectrum of outcomes that might be associated with infection during pregnancy and the factors that might increase risk to the fetus are not yet fully understood. More studies are planned to learn more about the risks of Zika virus infection during pregnancy.[42] In the worst affected region of Brazil approximately 1 percent of newborns are suspected of microcephaly.[43]

Key facts

  • Zika virus disease is caused by a virus transmitted by Aedes mosquitoes.
  • People with Zika virus disease usually have a mild fever, skin rash (exanthema) and conjunctivitis. These symptoms normally last for 2-7 days.
  • There is no specific treatment or vaccine currently available.
  • The best form of prevention is protection against mosquito bites.
  • The virus is known to circulate in Africa, the Americas, Asia and the Pacific.

Introduction

Zika virus is an emerging mosquito-borne virus that was first identified in Uganda in 1947 in rhesus monkeys through a monitoring network of sylvatic yellow fever. It was subsequently identified in humans in 1952 in Uganda and the United Republic of Tanzania. Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific.
  • Genre: Flavivirus
  • Vector: Aedes mosquitoes (which usually bite during the morning and late afternoon/evening hours)
  • Reservoir: Unknown

Signs and Symptoms

The incubation period (the time from exposure to symptoms) of Zika virus disease is not clear, but is likely to be a few days. The symptoms are similar to other arbovirus infections such as dengue, and include fever, skin rashes, conjunctivitis, muscle and joint pain, malaise, and headache. These symptoms are usually mild and last for 2-7 days.
During large outbreaks in French Polynesia and Brazil in 2013 and 2015 respectively, national health authorities reported potential neurological and auto-immune complications of Zika virus disease. Recently in Brazil, local health authorities have observed an increase in Zika virus infections in the general public as well as an increase in babies born with microcephaly in northeast Brazil. Agencies investigating the Zika outbreaks are finding an increasing body of evidence about the link between Zika virus and microcephaly. However, more investigation is needed before we understand the relationship between microcephaly in babies and the Zika virus. Other potential causes are also being investigated.

Transmission

Zika virus is transmitted to people through the bite of an infected mosquito from the Aedes genus, mainly Aedes aegypti in tropical regions. This is the same mosquito that transmits dengue, chikungunya and yellow fever.
Zika virus disease outbreaks were reported for the first time from the Pacific in 2007 and 2013 (Yap and French Polynesia, respectively), and in 2015 from the Americas (Brazil and Colombia) and Africa (Cape Verde). In addition, more than 13 countries in the Americas have reported sporadic Zika virus infections indicating rapid geographic expansion of Zika virus.

Diagnosis

Zika virus is diagnosed through PCR (polymerase chain reaction) and virus isolation from blood samples. Diagnosis by serology can be difficult as the virus can cross-react with other flaviviruses such as dengue, West Nile and yellow fever.

Prevention

Mosquitoes and their breeding sites pose a significant risk factor for Zika virus infection. Prevention and control relies on reducing mosquitoes through source reduction (removal and modification of breeding sites) and reducing contact between mosquitoes and people.
This can be done by using insect repellent; wearing clothes (preferably light-coloured) that cover as much of the body as possible; using physical barriers such as screens, closed doors and windows; and sleeping under mosquito nets. It is also important to empty, clean or cover containers that can hold water such as buckets, flower pots or tyres, so that places where mosquitoes can breed are removed.
Special attention and help should be given to those who may not be able to protect themselves adequately, such as young children, the sick or elderly.
During outbreaks, health authorities may advise that spraying of insecticides be carried out. Insecticides recommended by the WHO Pesticide Evaluation Scheme may also be used as larvicides to treat relatively large water containers.
Travellers should take the basic precautions described above to protect themselves from mosquito bites.

Treatment

Zika virus disease is usually relatively mild and requires no specific treatment. People sick with Zika virus should get plenty of rest, drink enough fluids, and treat pain and fever with common medicines. If symptoms worsen, they should seek medical care and advice. There is currently no vaccine available.

What is Zika virus infection?

Zika virus infection is caused by the bite of an infected Aedes mosquito, usually causing mild fever, rash, conjunctivitis, and muscle pain.  
The virus was isolated for the first time in 1947 in the Zika forest in Uganda. Since then, it has remained mainly in Africa, with small and sporadic outbreaks in Asia. In 2007, a major epidemic was reported on the island of Yap (Micronesia), where nearly 75% of the population was infected. 
On 3 March 2014, Chile notified PAHO/WHO that it had confirmed a case of indigenous transmission of Zika virus on Easter Island, where the virus continued to be detected until June 2014. 
In May 2015, the public health authorities of Brazil confirmed the transmission of Zika virus in the northeast of the country. Since October 2015, other countries and territories of the Americas have reported the presence of the virus. See updated list at: www.paho.org/zikavirus.

What are the symptoms?

The most common symptoms of Zika virus infection are mild fever and exanthema (skin rash), usually accompanied by conjunctivitis, muscle or joint pain, and general malaise that begins 2-7 days after the bite of an infected mosquito. 
One out of four infected people develops symptoms of the disease. Among those who do, the disease is usually mild and can last 2-7 days. Symptoms are similar to those of dengue or chikungunya, which are transmitted by the same type of mosquito. Neurological and autoimmune complications are infrequent, but have been described in the outbreaks in Polynesia and, more recently, in Brazil. As the virus spreads in the Americas, giving us more experience with its symptoms and complications, it will be possible to characterize the disease better. 

How is Zika virus transmitted? 

Zika virus is transmitted to people through the bite of an infected Aedes mosquito. This is the same mosquito that transmits dengue and chikungunya. 

Can it be transmitted through blood or sexual contact? 

In general, the Zika virus needs a vector (a means of transportation) to infect people. That vector is the mosquito. The virus has also been isolated in semen, and one case of possible person-to-person sexual transmission has been described, but not confirmed. 
Zika can be transmitted through blood, but this is an infrequent mechanism. The usual recommendations for safe transfusions should be followed (e.g., healthy volunteer donors).  

Can it be transmitted from mother to child?

There is little information on transmission from mother to baby during pregnancy or childbirth. Perinatal transmission has been reported with other vector-borne viruses, such as dengue and chikungunya. Studies are now being conducted on possible mother-to-child transmission of the virus and its possible effects on the baby. More information.  

What treatment is there?

Treatment consists of relieving pain, fever, and any other symptom that inconveniences the patient. To prevent dehydration, it is recommended to control the fever, rest, and drink plenty of water. There is no vaccine or specific drug for this virus. 

Can it cause death?

In this Region, it is a new virus that up until now has had a very limited geographical and demographic distribution, and there is no evidence that it can cause death. However, sporadic cases have been reported of more serious manifestations and complications in patients with preexisting diseases or conditions, causing death. 

Who is at risk of Zika infection? 

Anyone not previously exposed to the virus and who lives in an area where the mosquito is present, and where imported or local cases have been reported, may be infected. Since the Aedes mosquito is found throughout the Region (except in continental Chile and Canada), it is likely that outbreaks will occur in other countries that have not yet reported any cases. 

How is Zika diagnosed?

In most people, diagnosis is based on clinical symptoms and epidemiological circumstances (such as Zika outbreak in the patient’s area or trips to areas where the virus is circulating).
Blood tests can help to confirm the diagnosis. Some (virological PCR tests) are useful in the first 3-5 days after the onset of symptoms, while others (serological tests) detect the presence of antibodies but are useful only after five days. 
Once it has been demonstrated that the virus is present in a given area or territory, confirmation of all cases is not necessary, and laboratory testing will be adjusted to routine virological surveillance of the disease.  

Which is the difference between Zika, dengue, and chikungunya?

All these diseases present similar symptoms, but certain symptoms suggest one disease or another: 
Dengue usually presents with higher fever and more severe muscle pain. There can be complications when the fever breaks: attention should be paid to warning signs such as bleeding. 
Chikungunya presents with higher fever and more intense joint pain, affecting the hands, feet, knees, and back. It can disable people, bending them over so that they cannot walk or perform simple actions such as opening a water bottle. 
Zika does not have clearly characteristic features, but most patients have skin rashes and some have conjunctivitis. 

Is there a relationship between Guillain-Barré syndrome and Zika virus? 

An increase in Guillain-Barré syndrome (GBS) has been observed in areas where a Zika virus epidemic has been documented (e.g., in French Polynesia and Brazil). 
However, a direct causal relationship has not been established between Zika virus infection and GBS. Prior infection with dengue or genetic factors could contribute to or increase cases of GBS. Several studies are underway to better establish the relationship between Zika and GBS. 
GBS occurs when a person’s immune system attacks itself, in particular affecting the cells of the nervous system. This process can be initiated by infection with various viruses or bacteria. The main symptoms include muscular weakness and tingling (paresthesia) in the arms and legs, and severe complications can occur if the respiratory muscles are affected. The most seriously ill patients need attention in intensive care units.

CIRCULATION OF ZIKA VIRUS

Which countries have reported cases of Zika in the Americas? 

On 3 March 2014, Chile notified PAHO/WHO that it had confirmed a case of indigenous transmission of Zika virus on Easter Island, where the virus continued to be detected until June 2014. 
In May 2015, the public health authorities of Brazil confirmed the transmission of Zika virus in the northeast of the country. Since October 2015, other countries and territories of the Americas have reported the presence of the virus. (See updated list at: www.paho.org/zikavirus.

What causes rapid transmission in an area?

There are two factors for rapid transmission (documented in other countries): (1) Since this is a new virus to the Americas, the entire population is susceptible, lacking defenses to Zika virus; and (2) The Aedes mosquito is widespread in the Region, given the climatic conditions, temperature, and humidity in tropical countries. 

Is it advisable to travel to countries where Zika virus is circulating? 

PAHO/WHO does not recommend any travel or international trade restrictions related to Zika virus outbreaks. Travelers are advised to take the suggested precautions to prevent mosquito bites. 

How many Zika cases have been reported in the Region of the Americas? 

Countries begin reporting when they detect the circulation of the virus in their territories. However, maintaining a case count is difficult because symptoms of the disease tend to be mild and not everyone affected is seen by health services. What is most important is to detect the circulation of the virus, strengthen the response of health services, and step up surveillance of serious cases and complications. 

PREVENTION

What measures should be taken to prevent Zika virus infection? 

Prevention involves reducing mosquito populations and avoiding bites, which occur mainly during the day. Eliminating and controlling Aedes aegypti mosquito breeding sites reduces the chances that Zika, chikungunya, and dengue will be transmitted. An integrated response is required, involving action in several areas, including health, education, and the environment. 
To eliminate and control the mosquito, it is recommended to: 
  • Avoid allowing standing water in outdoor containers (flower pots, bottles, and containers that collect water) so that they do not become mosquito breeding sites. 
  • Cover domestic water tanks so that mosquitoes cannot get in. 
  • Avoid accumulating garbage: Put it in closed plastic bags and keep it in closed containers. 
  • Unblock drains that could accumulate standing water. 
  • Use screens and mosquito nets in windows and doors to reduce contact between mosquitoes and people. 
To prevent mosquito bites, it is recommended that people who live in areas where there are cases of the disease, as well as travelers and, especially, pregnant women should:  
  • Cover exposed skin with long-sleeved shirts, trousers, and hats
  • Use repellents recommended by the health authorities (and apply them as indicated on the label)
  • Sleep under mosquito nets. 
People with symptoms of Zika, dengue, or chikungunya should visit a health center. 

What is PAHO/WHO’s response in the Americas? 

PAHO/WHO is working actively with the countries of the Americas to develop or maintain their ability to detect and confirm cases of Zika virus infection, treat people affected by the disease, and implement effective strategies to reduce the presence of the mosquito and minimize the likelihood of an outbreak. PAHO/WHO’s support involves: 
  • Building the capacity of laboratories to detect the virus in a timely fashion (together with other collaborating centers and strategic partners). 
  • Advising on risk communication to respond to the introduction of the virus in the country. 
  • Controlling the vector by working actively with the populace to eliminate mosquito populations.
  • Preparing recommendations for the clinical care and monitoring of persons with Zika virus infection, in collaboration with professional associations and experts from the countries. 
  • Monitoring the geographic expansion of the virus and the emergence of complications and serious cases through surveillance of events and country reporting through the International Health Regulations channel.
  • Supporting health ministry initiatives aimed at learning more about the characteristics of the virus, its impact on health, and the possible consequences of infection.

Symptoms

  • About 1 in 5 people infected with Zika virus become ill (i.e., develop Zika).
  • The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week.
  • The illness is usually mild with symptoms lasting for several days to a week.
  • Zika virus usually remains in the blood of an infected person for a few days but it can be found longer in some people.
  • Severe disease requiring hospitalization is uncommon.
  • Deaths are rare.

Diagnosis

  • The symptoms of Zika are similar to those of dengue and chikungunya, diseases spread through the same mosquitoes that transmit Zika.
  • See your healthcare provider if you develop the symptoms described above and have visited an area where Zika is found.
  • If you have recently traveled, tell your healthcare provider when and where you traveled.
  • Your healthcare provider may order blood tests to look for Zika or other similar viruses like dengue or chikungunya.

Treatment

  • No vaccine or medications are available to prevent or treat Zika infections.
  • Treat the symptoms:
    • Get plenty of rest
    • Drink fluids to prevent dehydration
    • Take medicines, such as acetaminophen or paracetamol, to relieve fever and pain
    • Do not take aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), like ibuprofen and naproxen. Aspirin and NSAIDs should be avoided until dengue can be ruled out to reduce the risk of hemorrhage (bleeding). If you are taking medicine for another medical condition, talk to your healthcare provider before taking additional medication.
  • If you have Zika, avoid mosquito bites for the first week of your illness.
    • During the first week of infection, Zika virus can be found in the blood and passed from an infected person to another mosquito through mosquito bites.
    • An infected mosquito can then spread the virus to other people.

Zika virus


Photo: AP
The most common symptoms of the Zika disease are fever, rash, joint pain, and conjunctivitis (red eyes), usually lasting from several days to a week, and most patients don't need hospitalisation. However the outbreak in Brazil has led to instances of Guillain-Barre syndrome and pregnant women giving birth to babies with birth defects

How it spreads:

  • Through mosquitoes, which mostly spread the virus during the day
  • Through sexual transmission
  • Mosquitoes also spread dengue and chikungunya viruses
  • There is no vaccine

How to prevent it:

  • Avoid getting mosquito bites by using insect repellants, and wearing long-sleeved shirts and trousers
  • Use air conditioning and/or a window screen to keep mosquitoes outside
  • Sleep under a mosquito bed net
  • Reduce the number of mosquitoes by emptying standing water from containers such as flowerpots or bucket


Source: Centers for Disease Control and Prevention

Sumber : Internet

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