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Zika virus is a mosquito-borne flavivirus closely related to dengue virus. It was first isolated from a rhesus monkey in Zika forest, Uganda in 1947, in mosquitoes (Aedes africanus) in the same forest in 1948 and in humans in Nigeria in 1954. Zika virus is endemic in parts of Africa and Asia and was first identified in the South Pacific after an outbreak on Yap Island in the Federated States of Micronesia in 2007. Now it is being reported in Latin America, the US and Europe.

Some researchers think climate change may play a significant role in spreading of the Zika. As temperatures increase in some areas, mosquitoes can multiply more easily and quickly, potentially enhancing their  ability to transmit diseases. 

Zika virus is primarily transmitted to humans through bites from Aedes mosquitoes, which often live around buildings in urban areas and are usually active during daylight hours (peak biting activity occurs in early mornings and late afternoons). But now experts think  mosquitoes belonging to other genera too are spreading the disease.

Some evidence suggests Zika virus can also be transmitted to humans through blood transfusion, perinatal transmission and sexual transmission. However, these modes are very rare.

The incubation period is typically between 3 and 12 days.

Some facts about the virus according to World Health Organization...

Zika virus is transmitted to humans by infected mosquitoes. It causes mild fever and rash. Other symptoms include muscle pain, joint pain, headache, pain behind the eyes and conjunctivitis.
Zika virus disease is usually mild, with symptoms lasting only a few days.
The disease has similar clinical signs to dengue, and may be misdiagnosed in areas where dengue is common.
There is no cure for Zika virus disease. Treatment is focused on relieving the symptoms.

Prevention and control relies on reducing the breeding of Aedes mosquitoes through source reduction (removal and modification of breeding sites) and minimizing contact between mosquito vectors and people by using barriers (such as repellents, insect screens), reducing water-filled habitats supporting mosquito larvae in and close to dwellings, and reducing the adult mosquito populations around at-risk communities.

There is no commercial vaccine or specific antiviral drug treatment for Zika virus infection. Treatment is directed primarily at relieving symptoms using anti-pyretics and analgesics.

Scientists now think there is an interesting link between Zika virus infection of pregnant women and microcephaly condition of their new born children. The data to provide evidence linking the relatively mild mosquito-borne disease and babies born with small heads and potential brain damage, however, are not yet conclusive. To prove the connections between the two conditions researchers must study the documented microcephaly cases, the case history of pregnant women and conduct case-control studies of babies born in affected areas such as Brazil to get further insights. Only then, following careful analyses, can scientists solidify the Zika–microcephaly links and the required preventative steps can be taken.

In 2015 Brazil reported nearly 4,000 cases of an incurable condition, called microcephaly in infants (abnormally tiny heads, potentially debilitating brain damage with incomplete brain development) — many times more than the prior year. In the nation’s northeast, where most of the cases occurred, government officials have already declared a state of emergency. Now international researchers and Brazilian authorities are trying to control the condition. Although the Brazilian government has said there are almost 4,000 cases of microcephaly in the country, only six of the cases have been strongly linked to Zika virus via laboratory testing that confirms genetic material from the virus is present in the infant.

Scientists are strongly suspecting that a mosquito-borne disease  Zika  plaguing the same areas in Brazil is responsible for this as already there is evidence the virus can cross the placental barrier: Zika has been detected in the amniotic fluid of two pregnant women with microcephalic fetuses in the state of Paraiba. Therefore, the virus is capable of crossing the placental barrier. What’s more, viruses from the same genus have the ability to replicate once they reach the central nervous system, providing some indication of how the viruses could potentially cause microcephaly in the first place.

However, microcephaly is usually caused by exposure to toxic substances during pregnancy, genetic abnormalities or diseases during pregnancy like rubella or herpes. But we don't know much about zeka. Until recently, there were only sporadic cases of people infected with the virus (at least ones that were laboratory confirmed), with small outbreaks in Africa and Southeast Asia since being discovered in 1947 in Uganda. But now the Zika virus is rapidly advancing across new parts of the world.

In May 2015 Brazil reported its first case of Zika and by December 2015 the virus had made its way into several countries in Central and South America, such as Colombia and Mexico, and even showed up on the island of Puerto Rico. The rapid spread suggests a change in the Zika virus, one which scientists are racing against the clock to pinpoint. Worryingly, Zika has also been linked with the future development of Guillain–Barré syndrome, an autoimmune disease that could lead to paralysis. Analysis of an earlier outbreak of Zika in French Polynesia also separately suggests that there, too, was an increase in cases of neurological impairment.

Researchers know a virus like Zika could mutate to become more fit, essentially allowing it to transmit more easily from one host to another in order to survive. But a mutation designed specifically to help it cross the natural placental barrier between mother and fetus would not necessarily be too beneficial for the virus because it has been successfully transmitted in more traditional ways, according to Scott Weaver, an expert on mosquito-borne viral diseases at The University of Texas Medical Branch (U.T.M.B.) at Galveston. A more likely possibility for its rapid reach, he says, is that the virus may have adapted in recent years to have a higher level of viremia, or more virus present in any given drop of blood. That would allow Zika to be transmitted at a greater rate because it would increase the chances of a mosquito picking up the virus and transmitting it to another person after biting an infected human. A fringe benefit of this viremia would be that although the virus would not have any innate increase in its ability to cross the placental barrier, its high concentration may boost its chances of making the leap. A few strains of virus, according to some virologists,  could have achieved this. A team at U.T.M.B. is studying the virus now in the hopes of finding such answers.

The signs they are looking for lie in the newborns’ antibodies. Because the antibodies for Zika virus look so much like those for dengue or yellow fever, (both common in Brazil) it is hard to detect if a pregnant woman has contracted Zika or had one of those other conditions in the past. But lab testing of cord blood antibodies that show up in response to a recent exposure—called immunoglobulin M antibodies, or IgM—would allow scientists to detect if the fetus was infected with Zika and that it happened recently (unlike tests that would pick up longer term antibodies transmitted from the mom). Those tests, too, may also pick up similar-looking dengue virus and confuse the results, according to experts, but the chance of such a false positive is rare because fetal dengue infection is so uncommon. “By trying to diagnose more of these cases at birth by sampling cord blood, they may learn more about how these fetuses were infected”.

There is already some indication the Zika–microcephaly connection is more than just geographical coincidence. There have also been reports of genetic material from Zika being detected in the blood tissue of a microcephalic baby that died immediately after birth in the northern Brazilian state of Pará. And, anecdotally, some of the women who went on to birth children with microcephaly also remembered having a rash during pregnancy—a potential but not definitive symptom of Zika. There have been reports in French Polynesia too of an unusual uptick in central nervous system problems among babies born in the past couple years in areas associated with Zika outbreaks. Further lab testing of those mothers found that at least some of them may have had asymptomatic Zika virus.

The full scope of Zika-related birth defects may extend far beyond abnormally small heads and brain damage. Research suggests that serious joint problems, seizures, vision impairment, trouble feeding and persistent crying can be added to the list of risks from Zika exposure in the womb (1).

Investigations are continuing. If the new cord blood information and other research soon firms up the Zika–microcephaly connection, perhaps that will add further impetus to develop a vaccine for Zika—possibly by adapting one already in use for Zika’s close relative, dengue.

Like they say, prevention is better than cure. Controlling mosquito populations and protecting from mosquito bites can stop the spread of the disease.



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GM mosquitoes protect Brazilian city from Zika

The release of genetically modified (GM) mosquitoes whose offspring die before they become mature adults has slashed numbers of the insects in a Brazilian city in a state troubled by Zika fever.
Several million of the ‘friendly Aedes aegypti’ mosquito were released in a district of Piracicaba, in Sao Paulo state, in April 2015. By the end of the year, mosquito numbers in the area had plummeted by 82 per cent, according to Oxitec, the company that developed the mosquito.
The firm announced this month that it will work with Piracicaba municipality to build a local production facility that will continuously rear the GM mosquito for release (see chart). This could protect up to 300,000 people — the whole city — from mosquito-borne diseases such as Zika, dengue fever and chikungunya, according to Oxitec chief executive officer Hadyn Parry.

How Oxitec mosquitoes are produced 485.jpg
 Click here to enlarge Credit: Oxitec

“The GM mosquito does not perpetuate in nature: it dies two to four days after being released.”
The Aedes aegypti mosquito that spreads Zika fever is not native to Brazil, but was imported through international travel The use of the GM mosquito was approved in Brazil in 2014 after the national regulator for transgenic organisms decided the insects did not pose a significant risk to humans or the environment.


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Zika virus can live for hours on hard, non-porous surfaces

The Zika virus is most commonly transmitted in humans as the result of a bite from an infected mosquito or from an infected human to another human. What is not well known is that the virus also can be transmitted via the environment if an individual is pricked with an infected needle or has an open cut and comes in contact with the live virus. While there are no known cases to date of the general public being infected with the Zika virus through the environment, there has been at least one documented case of laboratory acquired Zika virus infection.

Research being presented today at the 2016 American Association of Pharmaceutical Scientist (AAPS) Annual Meeting and Exposition, which is taking place Nov. 13 -17 in Denver, found that under certain conditions, the Zika virus can live for several hours on hard non-porous surfaces and still be highly contagious, but that some commonly used disinfectants are extremely effective in killing the virus. The research may have important infection control implications for both consumers and those who work in healthcare or lab settings.

The study looked at isopropyl alcohol, diluted bleach, quaternary ammonium/alcohol, peracetic acid, and pH 4 or pH 10 solutions, which are commonly used in clinical, laboratory and industrial settings.

Findings showed that when the virus was in an environment without blood, these methods of inactivating Zika, except pH 4 and pH 10, were largely effective, but in environments where virus was associated with blood, the results were dramatically different.

"Zika can survive on hard, non-porous surfaces for as long as eight hours, possibly longer when the environment contains blood, which is more likely to occur in the real world," said the study's lead researcher S. Steve Zhou, Ph.D. "The good news is that we found that disinfectants such as isopropyl alcohol and quaternary ammonium/alcohol are generally effective in killing the virus in this type of environment and can do so in a little as 15 seconds."

Zhou, who is the director of virology and molecular biology for Microbac Laboratories, headquartered in Pittsburgh, Penn., said the study did not yet look at the survivability of Zika on hard non-porous surfaces beyond eight hours.

Microbac's research also found that bleach and peracetic acid were not as effective in killing Zika virus when the virus is associated with blood.

"The data were important to know especially for healthcare providers and researchers," said Zhou. "One must bear the organic load of the environment such as blood, in mind, before reaching a conclusion about the Zika virus inactivation efficacy by a particular product."

The next stage of the research will be to take a more in-depth look at how long Zika survives on hard non-porous surfaces in the heat and how best to inactivate the virus.

Story Source:

 American Association of Pharmaceutical Scientists


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