The World Health Organization has warned that the Zika virus is “spreading explosively” in the Americas and that as many as four million people could be infected by the end of the year. Officials at the Centers for Disease Control and Prevention have urged pregnant women against travel to about two dozen countries, mostly in the Caribbean and Latin America, where the outbreak is growing.
The infection appears to be linked to the development of unusually small heads andbrain damage in newborns. Some pregnant women who have been to these regions should be tested for the infection, the agency said. Here are some answers and advice about the outbreak.
UnitedStatesZIKA VIRUSEgyptMexicoPuertoRicoIndiaKenyaIndonesiaBrazilAreas with current or past evidence of ZikaAngolaEasterIsland1.What is the Zika virus?A tropical infection new to the Western Hemisphere.The Zika virus is a mosquito-transmitted infection related to dengue, yellow fever and West Nile virus. Although it was discovered in the Zika forest in Uganda in 1947 and is common in Africa and Asia, it did not begin spreading widely in the Western Hemisphere until last May, when an outbreak occurred in Brazil.Until now, almost no one on this side of the world had been infected. Few of us have immune defenses against the virus, so it is spreading rapidly. Millions of people in tropical regions of the Americas may now have been infected.Yet for most, the infection causes no symptoms and leads to no lasting harm. Scientific concern is focused on women who become infected while pregnant and those who develop a temporary form of paralysis after exposure to the Zika virus.
Aedes aegypti mosquitoes in a petri dish. Felipe Dana/Associated Press 2.How is the virus spread?Mosquitoes, but not every species.Zika is spread by mosquitoes of the Aedes species, which can breed in a pool of water as small as a bottle cap and usually bite during the day. The aggressive yellow fever mosquito, Aedes aegypti, has spread most Zika cases, but that mosquito is common in the United States only in Florida, along the Gulf Coast, and in Hawaii – although it has been found as far north as Washington, D.C., in hot weather.The Asian tiger mosquito, Aedes albopictus, is also known to transmit the virus, but it is not clear how efficiently. That mosquito ranges as far north as New York and Chicago in summer.Although the virus is normally spread by mosquitoes, there has been one report of possible spread through blood transfusion and one of possible spread through sex. The virus was found on one occasion in semen.- 3.How might Zika cause brain damage in infants?Experts aren’t certain how it happens, or even whether the virus is to blame.The possibility that the Zika virus causes microcephaly – unusually small heads and damaged brains – emerged only in October, when doctors in northern Brazil noticed a surge in babies with the condition.It may be that other factors, such as simultaneous infection with other viruses, are contributing to the rise; investigators may even find that Zika virus is not the main cause, although right now circumstantial evidence suggests that it is.It is not known how common microcephaly has become in Brazil’s outbreak. About three million babies are born in Brazil each year. Normally, about 150 cases of microcephaly are reported, and Brazil says it is investigating nearly 4,000 cases. Yet reported cases usually increase when people are alerted to a potential health crisis.
- 4.What is microcephaly?Babies with microcephaly have unusually small heads. In roughly 15 percent of cases, a small head is just a small head, and there is no effect on the infant, according to Dr. Constantine Stratakis, a pediatric geneticist and a scientific director at the National Institute of Child Health and Human Development.But in the remainder of cases, the infant’s brain may not have developed properly during pregnancy or may have stopped growing in the first years of life. These children may experience a range of problems, like developmental delays, intellectual deficits or hearing loss.The consequences can vary widely from child to child. Pinpointing an underlying cause helps clinicians to advise parents about their newborn’s prognosis.Genetic abnormalities are a common cause. Microcephaly can also be triggered by infections of the fetus, including German measles (also known as rubella), toxoplasmosis (a disease caused by a parasite, often in cat feces) andcytomegalovirus.Microcephaly may also result if a pregnant woman consumes alcohol, is severely malnourished or has diabetes. If the defect occurs in a child’s first years, it may be a result of a brain injury during labor.There is no treatment for an unusually small head.“There is no way to fix the problem, just therapies to deal with the downstream consequences,” said Dr. Hannah M. Tully, a neurologist at Seattle Children’s Hospital who specializes in brain malformations.
United StatesATLANTICOCEANHaitiDominican RepublicPuerto RicoGuadeloupeSt. MartinMartiniqueBarbadosU.S. Virgin IslandsMexicoCubaGuatemalaHondurasEl SalvadorPanamaVenezuelaGuyanaSurinameFrench GuianaColombiaEcuadorBrazilPACIFICOCEANPeruBoliviaAreaspregnant womenshould avoidParaguayArgentinaNote: Cape Verde and American Samoa should also be avoided.5.What countries should pregnant women avoid?About two dozen destinations mostly in the Caribbean, Central America and South America.The Pan American Health Organization believes that the virus will spread locally in every country in the Americas except Canada and Chile. Here is the C.D.C.’s current list of countries and territories in which Zika virus is circulating. The latest updates are here.- 6.How do I know if I’ve been infected? Is there a test?It’s often a silent infection, and hard to diagnose.Until recently, Zika was not considered a major threat because its symptoms are relatively mild. Only one of five people infected with the virus develop symptoms, which can include fever, rash, joint pain and red eyes. Those infected usually do not have to be hospitalized.There is no widely available test for Zika infection. Because it is closely related to dengue and yellow fever, it may cross-react with antibody tests for those viruses. To detect Zika, a blood or tissue sample from the first week in the infection must be sent to an advanced laboratory so the virus can be detected through sophisticated molecular testing.
The C.D.C. testing algorithm for pregnant women who have visited countries in which the Zika virus is spreading. Centers for Disease Control and Prevention 7.I’m pregnant and I recently visited a country with Zika virus. What do I do?Some women should get blood tests, and just about all should get ultrasound scans.On Jan. 19, the C.D.C. issued interim guidelines for women in that situation and for their doctors. The guidelines are complex — and may change.In general, they say that pregnant women who have visited any area with Zika transmission should consult a doctor. Those who have had symptoms of infection like fever, rash, joint pain and bloodshot eyes during their trip or within two weeks of returning should have a blood test for the virus.That recommendation is controversial, because even women with no symptoms may have been infected — 80 percent of those who get the virus do not feel ill — and there is no evidence that babies are hurt only when the mother has been visibly ill. But at the time the guidelines were issued, the C.D.C. and state health departments simply did not have the laboratory capacity to test every pregnant woman who visited Latin America and the Caribbean in the last nine months, as well as every pregnant woman in Puerto Rico.Even for women who get blood tests, the news is not entirely reassuring. Tests for the virus itself only work in the first week or so after infection. Tests for antibodies can be done later, but they may yield false positives if the woman has had dengue, yellow fever or even a yellow fever vaccine.Under the C.D.C’s testing algorithm, pregnant women who have been to affected regions – whether they have symptoms or not, and whether they have negative or positive blood tests – should eventually have an ultrasound scan to see if their fetuses are developing microcephaly or calcification of the skull.Unfortunately, an ultrasound usually cannot detect microcephaly before the end of the second trimester.Some women also should have amniocentesis to test the fluid around the fetus for Zika virus. But amniocentesis involves piercing the amniotic sac with a long needle through the abdomen; it is slightly risky for the fetus and is not recommended before 15 weeks gestation.Several companies are working on rapid tests for Zika infection. The C.D.C. also usually distributes test kits and training materials to state health departments during outbreaks, which should increase testing capacity.- 8.I’m of childbearing age, but not pregnant and not planning to get pregnant. Should I go to an affected country?Only if you use birth control religiously.Half of pregnancies are unintended. If you want to visit a country where Zika transmission has been reported, Dr. Laura E. Riley, a specialist who works with high-risk pregnancies and infectious disease at Massachusetts General Hospital, advises strict use of birth control to ensure you don’t get pregnant.Women who become unexpectedly pregnant while traveling or shortly afterward will face blood tests, monthly ultrasounds and a great deal of anxiety.“Why would you ever sign yourself up for that?” said Dr. Riley. “There’s enough in life to worry about. I wouldn’t add that to my list.”
- 9.I’m pregnant now, but wasn’t when I visited one of the affected countries. What’s the risk?Very low, experts say.With rare exceptions, the virus does not appear to linger in the body, and people who recover from the infection are immune.“Our understanding, thus far, is that the risk is very, very low if you were in that place prior to conception,” said Dr. Laura E. Riley of Massachusetts General Hospital.“I wouldn’t be worried about if you conceived after you got back to the U.S.”
- 10.Does it matter when in her pregnancy a woman is infected with Zika virus?Earlier in pregnancy seems to be more dangerous.The most dangerous time is thought to be during the first trimester – when some women do not realize they are pregnant. Experts do not know how the virus enters the placenta and damages the growing brain of the fetus.Closely related viruses, including yellow fever, dengue and West Nile, do not normally do so. Viruses from other families, including rubella (German measles) and cytomegalovirus, sometimes do.
- 11.Should infants be tested?Other birth defects may be linked to the virus.Federal health officials say that newborns should be tested for infection with the Zika virus if their mothers have visited or lived in any country experiencing an outbreak and if the mothers’ own tests are positive or inconclusive.The reason, officials said in interviews, is that infection with the virus could be linked to defects in vision and hearing, among other abnormalities, even if the child does not suffer microcephaly. The other defects may require further assessments and testing.The new guidance applies only to infants of mothers who reported symptoms of Zika virus infection — a rash, joint pain, red eyes or fever — while living abroad in an affected country or within two weeks of travel to such a destination.
- No.The C.D.C. does not recommend a particular antiviral medication for people infected with the Zika virus. The symptoms are mild – when they appear at all – and usually require only rest, nourishment and other supportive care.
Health workers sprayed insecticide in the Sambadrome in Rio de Janeiro as part of a campaign to combat mosquitoes, which transmit the Zika virus. 13.Is there a vaccine? How should people protect themselves?Protection is difficult in mosquito-infested regions.There is no vaccine against the Zika virus. Efforts to make one have just begun, and creating and testing a vaccine normally takes years and costs hundreds of millions of dollars.Because it is impossible to completely prevent mosquito bites, the C.D.C. has advised pregnant women to avoid going to regions where Zika is being transmitted, and has advised women thinking of becoming pregnant to consult doctors before going.Travelers to these countries are advised to avoid or minimize mosquito bites by staying in screened or air-conditioned rooms or sleeping under mosquito nets, wearing insect repellent at all times and wearing long pants, long sleeves, shoes and hats.- Source : nytimes
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