The World Health Organization has declared the Zika virus an international public health emergency, prompted by growing concern that it could cause birth defects. 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.
1. What is the Zika virus?2. How does a mosquito transmit Zika?3. What areas is Zika likely to reach?4. Can the Zika virus be sexually transmitted?5. How might Zika cause brain damage in infants?6. What is microcephaly?7. What countries should pregnant women avoid?8. How do I know if I’ve been infected? Is there a test?9. I’m pregnant and I recently visited a country with Zika virus. What do I do?10. I’m of childbearing age, but not pregnant and not planning to get pregnant. Should I go to an affected country?11. I’m pregnant now, but wasn’t when I visited one of the affected countries. What’s the risk?12. I’ve just returned from a place where Zika virus is spreading but experienced no symptoms. How long until I can be sure I can’t pass on an asymptomatic infection?13. Does it matter when in her pregnancy a woman is infected with Zika virus?14. Should infants be tested?15. Is there a treatment?16. Is there a vaccine? How should people protect themselves?17. If Zika virus has been in Africa and Asia for decades, why wasn’t a link to microcephaly detected earlier?18. Outside of Brazil has a Zika outbreak ever been linked to microcephaly?
UnitedStatesZIKA VIRUSEgyptMexicoIndiaKenyaIndonesiaBrazilAreas 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 people here 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.
2 Infected bloodtravels to the midgut.1 Mosquito feeds onvirus-infected blood.3 Virus enters thecirculatory system ...How mosquitoesspread ZikaAedes aegyptimosquitoPATH OFTHE VIRUS4 ... and travels tothe salivary glands.5 Mosquito bites again, injecting virus-infected saliva into victim before feeding.2.How does a mosquito transmit Zika?The virus moves from its gut to its salivary glands.Only female mosquitoes bite people: they need blood in order to lay eggs. They pick up the virus in the blood. It travels from their gut through their circulatory system to their salivary glands and is injected into its next human victim. Mosquito saliva contains proteins that keeps blood from clotting. When a mosquito bites it first injects saliva so that its prey’s blood does not clog its straw-like proboscis.
UNITEDSTATESATLANTICOCEANMEXICOVENEZUELAPANAMACOLOMBIAPACIFICOCEANECUADORBRAZILPERUBOLIVIA100%Probable rangeof the yellowfever mosquito,Aedes aegyptiPARAGUAY50%0%ARGENTINA3.What areas is Zika likely to reach?Zika is spread by mosquitoes of the Aedes genus, 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.- 4.Can the Zika virus be sexually transmitted?Yes, but experts suspect that it rarely happens.Experts believe that the vast majority of all Zika infections are transmitted by mosquitoes, not sex. As of Feb. 2, there have only been three reports suggesting sexual transmission.
- In 2008, a scientist studying malaria in Africa returned to Colorado and apparently infected his wife before developing symptoms himself. Both had fever, rash and headaches. A year later, tests on their blood, which had been frozen, revealed that both had had Zika.
- In 2013, live virus was found in the semen of a 44-year-old Tahitian man; whether he infected anyone is unknown.
- In early February, health officials in Texas announced that a traveler who had returned to Dallas from Venezuela apparently had infected a sexual partner.
In the first two cases, the men had genital pain and blood in their semen, suggesting that their testes or prostates had been infected. Details regarding the third case were not released.Based on these reports, the C.D.C. issued tentative new guidelines suggesting that pregnant women avoid contact with semen from men who have recently returned from areas with Zika transmission. Men returning from these regions should consider using condoms, the agency said.Officials did not provide guidance on how long to do so. British health authorities have suggested using condoms for at least 28 days.There are still many unknowns, including:- Can a woman pass the virus to a man through sex? Can it be passed through anal, oral or any other form of sex?
- Does a man have to have blood in his semen to be infectious? Is he infectious before the blood appears?
- If there is no blood, does he have to have had Zika symptoms like fever and rash to transmit the virus? How long does a man remain infectious?
- 5.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 often 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.
ATLANTICOCEANVENEZUELAPANAMAPACIFICOCEANCOLOMBIAECUADORBRAZILPERURecifeBOLIVIAMicrocephaly cases in BrazilBy state, as of Feb. 13Rio de JaneiroARGENTINA101001,00010100Possible casesunder investigationConfirmedcases6.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 found in undercooked contaminated meat and cat feces) and cytomegalovirus.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 StatesHaitiDominican RepublicPuerto RicoGuadeloupeSt. MartinMartiniqueBarbadosU.S. Virgin IslandsCuraçaoTrinadad and TobagoATLANTICOCEANMexicoCubaJamaicaGuatemalaHondurasEl SalvadorNicaraguaCosta RicaGuyanaSurinameFrench GuianaVenezuelaPanamaColombiaEcuadorPACIFICOCEANBrazilPeruAreaspregnant womenshould avoidBoliviaParaguayArgentinaNote: American Samoa, Cape Verde, Tonga and the Marshall Islands should also be avoided.7.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.- 8.How do I know if I’ve been infected? Is there a test?It’s often a silent infection, and is 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 9.
