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Tuesday, February 2, 2016

What is Zika? வைரஸ் நோயான 'சிக்கா'

Q: What is Zika?


A: It’s an arbovirus, a broad classification, which means it is a virus that is transmitted by an arthropod — a mosquito, a tick, or a flea. More specifically, it is from a family of viruses called flaviviruses. You likely have heard of some other viruses in that disease-causing family: West Nile virus, dengue virus, and yellow fever virus.

Q: Why is it called Zika?

A: The virus was named after the region where it was found — in the Zika Forest of Uganda — in 1947.

Q: What is the infection like? Are there any treatments or vaccines?

A: Zika typically causes a mild infection. Flu-like symptoms — fatigue, aches, and pains — are most commonly reported, along with a skin rash. It often goes undiagnosed; people infected may not seek medical care. When they do, it can be confused for a mild case of dengue fever. Some tests can’t distinguish between the two.
There is no specific treatment. There is no vaccine to prevent infection and a vaccine will be difficult to develop.
It is suspected that Zika infection may trigger lifelong immunity to the virus, says Ann Powers, an arbovirus expert with the Centers for Disease Control and Prevention’s National Center for Emerging Zoonotic and Infectious Diseases. If that turns out to be true, people who have been infected could not be reinfected.

Q: Don’t the experts know whether it triggers lifelong immunity?

Surprisingly little is known about Zika virus. It hasn’t been studied much in the past because it wasn’t thought to be a significant cause of human disease.
It started to garner more scientific attention, though, in 2007 when there was an unexpected Zika outbreak in Yap, an island that is part of Micronesia. Then, in 2013, there was an outbreak in French Polynesia. The virus was on the move. Since Brazil reported its first cases last May, a series of South and Central American countries have diagnosed Zika infections.

Q: Is microcephaly the only serious suspected complication of Zika infection?

A: No. There is also a suspicion it is linked to an increase in cases of Guillain-Barré syndrome, a condition in which progressive paralysis sets in. Patients generally recover fully, but there are rare fatal cases. GBS has been linked to other infections, including influenza.

Q: How does it spread?

A: Aedes mosquitos transmit Zika virus. Mosquitoes become infected by taking a blood meal from an infected person and then they pass the virus as they bite other people. There is also evidence that Zika virus can be transmitted through sex.

Q: Do Aedes mosquitos circulate in the United States?

A: They do.
The southern United States has Aedes aegypti mosquitoes, which can transmit Zika virus. Another type, Aedes albopictus, is hardier and has a range that goes farther north. Lab work suggests they can transmit Zika virus, but it is not clear yet if they are or will be a big player in the spread of the virus.

Q: So, do experts expect Zika virus to circulate in the US?

A: There has already been a case of locally acquired Zika in Puerto Rico. But to date, transmission has not been detected on the US mainland, Hawaii, or Alaska. That said, a number of Americans have already been infected by Zika virus, having contracted it while traveling outside the country.
Experts think it is possible and even likely that parts of the United States, particularly the South, could see small clusters of cases. This is the scenario they envisage: Travelers come home with virus in their blood and are bitten by mosquitoes, which then bite other people. That scene played out in Florida in 2014 with Chikungunya virus, another mosquito-borne virus.
But the experts say such clusters are likely to be small and contained.

Q: Why?

A: You can thank air conditioning and screens.
Aedes mosquitoes are day-biting bugs that like to live in houses and near people. But it is easier for them to do that where window and door screens are not common and where houses are not closed up to maximize the effect of air conditioning.
Dr. Lyle Petersen, director of the CDC’s division of vector-borne diseases, says the agency thinks Zika virus spread in the United States will play out the way spread of dengue virus has. The CDC has studied eight or nine dengue outbreaks along the Texas-Mexico border. In Texas, the outbreaks are far smaller.
“What we see is there’s plenty of mosquitoes on both sides of the border but we see much less infection on the US side,” said Petersen. “It really does appear that the difference is lifestyle.”
Petersen adds an important caveat, though: “This is a new virus and we don’t know what it’s exactly going to do.”

 Q: Why would infection with Zika virus during pregnancy cause brain development to be stunted in the developing fetus?

A: No one knows, yet.
That said, it is known that infection during pregnancy with some other viruses — rubella and cytomegalovirus or CMV — increases the risk of microcephaly in the infant, says Scott Weaver, director of the Institute for Human Infections and Immunity at the University of Texas Medical Branch in Galveston.

Q: What is the evidence for a link between Zika infection and microcephaly?

A: The evidence is largely circumstantial, Weaver says. The sharp rise in the number of babies born with the condition started a few months after the virus arrived. And microcephaly cases have increased in places where lots of Zika cases were diagnosed.
But more persuasive evidence is starting to emerge. Brazilian scientists found traces of Zika virus in amniotic fluid from two women who were carrying fetuses identified as having microcephaly.
And scientists at the CDC have found traces of the virus in brain tissue from two infants with microcephaly who died shortly after birth, as well as in the placenta from two women who miscarried fetuses with the condition.

Q: If the link is real, why haven’t microcephaly cases increased in other places where Zika outbreaks have occurred?

A: Health officials in French Polynesia searched the country’s records for microcephaly cases after hearing of what was happening in Brazil, the CDC’s Peterson says. Where they would normally see no cases or maybe one in a year, they saw 12 in the months after their Zika outbreak.
As for the lack of reports from other countries of Latin America and the Caribbean where Zika virus has been spreading, it may just be that women infected during pregnancy haven’t yet started to give birth, Weaver says.
Also, if a condition is rare, it can be hard to see that there’s been an increase if you are looking in a small population. French Polynesia only saw the increase once they went looking for it. But in Brazil, with more than 200 million people, an increase is easier to see.
Says Weaver: “I think the lack of reporting in other countries is not informative at this point.”

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 medicine such as acetaminophen 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, prevent mosquito bites[PDF - 2 pages] 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.
அமெரிக்கா மற்றும் ஐரோப்பிய நாடுகளில் வேகமாக பரவிவரும் வைரஸ் நோயான 'சிக்கா' நுளம்புகளால் இந்தியா, இலங்கை உள்ளிட்ட ஆசியநாடுகளுக்கும் ஸிக்கா நோய் பரவலாம் என உலக சுகாதார நிறுவனம் எச்சரித்துள்ளது.
டெங்கு மற்றும் சிக்கன் குனியாவுக்கு காரணமான நுளம்புகளின் வாயிலாக கடந்த ஆண்டு பிரேசிலில் தோன்றிய சிக்கா நோயானது ரியோ டி ஜெனிரோ உள்ளிட்ட 24 அமெரிக்க நாடுகளிலும் ஐரோப்பிய கண்டத்தில் உள்ள சில நாடுகளிலும் படுவேகமாக பரவி வருகின்றது.

தாயின் கருவில் வளரும் குழந்தைகளின் மூளை வளர்ச்சியை இந்த நோய் பாதிப்படையச் செய்கிறது. இதனால், சிக்கா பாதிப்புடன் பிறக்கும் குழந்தைகள் சிறிய தலைகளுடன் காணப்படுகின்றன. இந்நோயானது, சிக்குன் குனியா, டெங்கு உள்ளிட்ட நோய்களை பரப்பும் ‘ஏடிஸ்’ நுளம்புகளால் பரவுவதாக முதலில் தெரிவிக்கப்பட்டது. ஆனால், செக்ஸ் (பாலியல் உறவு) மூலமாகவும் சிக்கா பரவுவதாக தற்போது கண்டறியப்பட்டுள்ளது.

இந்நோயை குணப்படுத்தும் மருந்துகளோ, தடுப்பு மருந்துகளோ இதுவரை கண்டுபிடிக்கப்படவில்லை. ஏற்கனவே பிரேசில் நாட்டில் ஆயிரத்துக்கும் அதிகமான குழந்தைகள் சிக்கா நோய் பாதிப்புடன் பிறந்துள்ளன என்பது குறிப்பிடத்தக்கது.

ஆசியா கண்டத்துக்கும் வேகமாக பரவ தொடங்கியுள்ள சிக்கா வைரஸ் தொடர்பாக உலக சுகாதார நிறுவனமான "WHO" கவலை தெரிவித்துள்ளது. சிக்கா வைரஸ் கிருமிகள் மிக வீரியத்துடன் பரவி வருவதாக உலக சுகாதார நிறுவனத்தின் தலைவரான மார்கரெட் சான் குறிப்பிட்டுள்ளார்.

சுமார் 40 லட்சம் மக்களை இந்நோய் தாக்கக்கூடும் என மதிப்பிட்டுள்ள உலக சுகாதார நிறுவனத்தின் தொற்று நோய்த்துறை இயக்குனரான டாக்டர் மார்கோஸ் எஸ்பினல், நுளம்புகள் எங்கெல்லாம் உள்ளனவோ., அங்கெல்லாம் சிக்கா நோய் செல்லக்கூடும். அது பரவும் வரை நாம் காத்திருக்க கூடாது என எச்சரித்துள்ளார். சிக்கா தடுப்பு மருந்து இந்த ஆண்டுக்குள் அறிமுகம் ஆகலாம்

படுவேகமாக பரவிவரும் கொடிய உயிர்க்கொல்லியான சிக்கா நோய்க்கு எதிரான தடுப்பு மருந்து இந்த ஆண்டின் இறுதிக்குள் அறிமுகம் ஆகலாம் என தெரியவந்துள்ளது. அமெரிக்கா, கனடா, தென்கொரியா உள்ளிட்ட நாடுகளைச் சேர்ந்த மருத்துவ பல்கலைக்கழக ஆராய்ச்சியாளர்கள் இந்த தடுப்பு மருந்தை கண்டுபிடிக்கும் ஆய்வில் மிகத் தீவிரமாக ஈடுபட்டு வருகின்றனர். இதில் ஓரளவுக்கு பலன் கிடைத்துள்ளதாகவும் செப்டம்பர் மாதமளவில் இதை பரிசோதிக்கும் முதல்கட்ட சோதனை நடத்தப்படும். பின்னர், உலக சுகாதார நிறுவனத்தின் அனுமதிக்கு அனுப்பிவைக்கப்பட்டு ஒருமாதத்துக்கு பிறகு அவசர தேவைக்காக அனுப்பி வைக்கப்படும் என இந்த ஆய்வுக்குழுவில் இடம்பெற்றுள்ள மூத்த டாக்டர்களில் ஒருவரான கேரி கோபின்கர் தெரிவித்துள்ளார்.
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