Where the Zika virus come from
First isolated in 1947 and first described in an article? 1952 Zika has long been known to occur in Africa and South Asia, but until there ten years, less than 15 cases have been described in the scientific literature. In 07, the virus caused a large outbreak in Yap, a group of islands in the western Pacific that is part of the Federated States of Micronesia; since then it has made a major tour of other Pacific islands before he landed in Brazil, where he began to spread quickly to other parts of South America, Central America, Mexico and the Caribbean.
Why has it exploded so suddenly
there may have been large epidemics in Africa and Asia in the past that was not detected ?; scientists did not pay much attention. But the current epidemic is a massive event waiting to happen. Latin America has a large number of A. aegypti , also known as the yellow fever mosquito, an important vector for Zika. (The tiger mosquito, A. albopictus , which is on the rise around the world, is considered a vector as well.) In addition, in the Americas had immunity to the virus. Travel makes things worse. Aedes mosquitoes do not fly more than a few hundred meters during their life; Zika moves from city to city and country to another when infected people receive on cars, buses, trains and planes.
These factors combined mean that the virus has the ability to spread far and fast once he had arrived.
Will Zika across the United States and Europe?
the United States and Europe have already seen "imported cases" -the people who arrived a Zika affected countries carrier of the virus. This was widely expected given the size of the epidemic in Latin America. The key question is whether there will be local homes-that is, the mosquitoes spread the virus from person to person. There is certainly a chance; A. albopictus occurs in several countries in Southern Europe (and it can move to the north), while the southern and eastern United States have populations of both A . aegypti and A. albopictus .
If so, scientists expect epidemics to be much lower than anywhere else on the basis of past experience with diseases transmitted by mosquitoes. Recent outbreaks of dengue fever in Florida, Texas and Hawaii were not sickened more than a few hundred people, for example; an outbreak of a disease transmitted by mosquitoes called chikungunya in northern Italy in 07, which began when a man infected with the virus arrived from India-ended after 197 cases. One reason that the epidemics in these countries tend to be smaller may be that people spend less time outdoors and live in homes that are harder for mosquitoes to enter; the size of mosquito populations may play a role as well.
Do we know for certain that Zika is causing an increase in birth defects?
No. There are strong indications that the areas in Brazil hit hard by Zika experienced a sharp increase in the number of babies born with microcephaly, a condition in which the head is much smaller than normal because the brain fails to develop properly. But it will take at least several months before results of the first case-control studies of pregnant women infected with Zika are available. Doctors in Brazil first noticed the increased cases of microcephaly for ultrasounds for pregnant women in June and July, months after the surge of Zika infections. expert in fetal medicine Manoel Sarno, who works at the Federal University of Bahia, said the pattern of brain damage he sees now appears separate from microcephaly caused by other infections, such as cytomegalovirus (CMV) or rubella. He and his colleagues began a study in August following Zika infected women during pregnancy; the results could come out late summer. Similar studies are underway elsewhere in Brazil and Colombia.
Are there other pressing issues that the scientists involved?
Plenty. Scientists are struggling to determine who was infected and who is not because the diagnostic tests have limitations. The tests, which detect the most accurate of the viral RNA in the blood of patient work within a week of the first symptoms appear. After this period, researchers can test the antibodies in the blood. But current testing for Zika antibodies cross-react with antibodies to dengue, which is so widespread in Brazil and much of the rest of Latin America-that almost all adults have antibodies to it. It is therefore difficult to say whether the mother of a baby born with microcephaly has been infected by Zika earlier in her pregnancy.
The researchers would also like to know how often Zika is transmitted through sexual contact. American scientist who caught the virus in Africa adopted his wife after getting home in 08, and a second case of alleged sexual transmission arrived in French Polynesia in 2013. But researchers have no idea what that risk is . ( "If I'm a man and I'm symptoms Zika, I wait a few months before having unprotected sex," virologist Scott Weaver of the University of Texas Medical Branch in Galveston recently said The New York Times .)
What drugs are available against Zika?
None. Until last year, Zika was so rare, and believed to be so sweet, that nobody cared to look for drug candidates. Even now that the virus is surging, it is not obvious that there is a large market for an antiviral drug, because the vast majority of infected people have very . few symptoms or none at all and it is not known that a drug could prevent birth defects when women Zika contract during pregnancy when they become infected and develop symptoms, it may be too late to avoid such damages. A vaccine against Zika can offer more hope to prevent microcephaly.
And when can we expect a vaccine?
It will take years. Several groups have started making vaccine candidates Zika, a process that will take at least several months. Most of these vaccine approaches are piggybacking on existing vaccines. For example, many vaccines are made by assembling proteins from the surface of a pathogen in a harmless virus or vector; who is now with Zika tried using these vectors. Once a candidate is made, it should be tested in animals before humans.Human tests start with small safety studies and move on to larger studies that verify if the product candidate is working. All it usually takes 10 to 15 months. Given the urgency, the time may be compressed, but even so, Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, said STAT he can be at least 5 to 7 years before that a Zika vaccine is commercially available.
So what can we do to stop the spread of the virus?
stop mosquitoes from biting people. Countries and communities can try to reduce mosquito populations by eliminating small reservoirs such as water flower pots, empty bottles, and scrap tires that Aedes mosquitoes like to breed. People can also reduce their especially significant personal exposure for women who are or may become pregnant by putting screens on windows, covering their skin, and using insect repellent. However, history has shown that the impact of the fight against mosquitoes on epidemics is modest at best, and they are difficult to maintain.
There must be better ways to fight against mosquitoes?
Not yet, but they are in the works. A British biotech called Oxitec, which was recently bought by Intrexon, a US company, has developed synthetic biology A. aegypti mosquitoes containing a gene construct that will kill their offspring before they reach the age adult. When a substantial number of males of this strain are released into the wild, they will mate with local females produce offspring that are not viable, which has been shown to make a dent in the population.
In another line of research, scientists infect A. aegypti with a bacterium called Wolbachia , which reduces the ability of mosquitoes to transmit diseases. developing the researchers, these approaches were mostly thinking about dengue, but the rise of Zika is to give their efforts a new sense of urgency. But again, it will take several years before these strategies are ready for prime time.
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