Q) What is Zika virus?
Zika virus is a mosquito-borne single-stranded RNA virus related to dengue virus. In the Americas, Zika virus is primarily transmitted by Aedes aegypti, but Aedes albopictus mosquitoes can also transmit the virus.
Q) How is Zika virus transmitted?
Zika virus is transmitted to humans primarily through the bite of an infected Aedes species mosquito. Aedes mosquitoes are aggressive daytime biters and feed both indoors and outdoors. They can also bite at night. Zika virus can be transmitted from a pregnant mother to her fetus during pregnancy or around the time of birth. We do not know how often Zika perinatal transmission occurs.
Q)Who is at risk of being infected?
Anyone who is living in or traveling to an area where Zika virus is found who has not already been infected with Zika virus. Specific areas where Zika virus transmission is ongoing are often difficult to determine and are likely to change over time. Please visit CDC’s Zika Travel Information webpage for the most updated information.
Q) What are symptoms of Zika virus infection?
About 1 in 5 people infected with Zika virus become symptomatic. Characteristic clinical findings are acute onset of fever with maculopapular rash, arthralgia, or conjunctivitis. Other commonly reported symptoms include myalgia and headache. Clinical illness is usually mild with symptoms lasting for several days to a week.
Q) Are there known complications of Zika virus infection?
There have been cases of Guillain-Barré syndrome reported in patients following suspected Zika virus infection. The relationship between Zika virus infection and Guillain-Barré syndrome is not known.
Laboratory testingQ) What types of testing for Zika virus are available to test pregnant women?
During the first week of illness, Zika virus disease can often be diagnosed by performing reverse transcriptase-polymerase chain reaction (RT-PCR) on serum. Serology assays can also be used to detect Zika virus-specific IgM and neutralizing antibodies, which typically develop toward the end of the first week of illness. Plaque-reduction neutralization testing (PRNT) can be performed to measure virus-specific neutralizing antibodies to confirm primary flavivirus infections and differentiate from other viral illnesses
Q) What are the challenges in interpreting Zika virus testing?
RT-PCR test may not demonstrate Zika virus RNA in a woman with Zika virus infection if the period of viremia has passed. Serum serologic testing can be performed, however, cross-reactivity with related flaviviruses (e.g., dengue, and yellow fever viruses) is common. Plaque-reduction neutralization testing (PRNT) can be performed to measure virus-specific neutralizing antibodies to Zika virus, but neutralizing antibodies may still yield cross-reactive results in persons who were previously infected with another flavivirus, such as dengue, or has been vaccinated against yellow fever or Japanese encephalitis. It is important to work closely with your state or local health department to ensure the appropriate test is ordered and interpreted correctly.
Q) How can Zika virus infection be prevented?
There is no vaccine to prevent Zika virus infection. Travelers can protect themselves by taking steps to prevent mosquito bites. Use insect repellent; wear long-sleeved shirts and long pants; and stay in places with air conditioning or with window and door screens. Pregnant women can and should choose an EPA-registered insect repellents and use it according to the product label.
Zika and PregnancyQ) What is known about the effects of Zika virus on pregnant women?
We expect that the course of Zika virus disease is similar to that in the general population. No evidence exists to suggest that pregnant women are more susceptible or experience more severe disease during pregnancy. It is not known if pregnant women are more susceptible to Guillain-Barré syndrome.
Q) Is there any association between Zika virus infection and congenital microcephaly?
There have been reports of congenital microcephaly in babies of mothers who were infected with Zika virus while pregnant. Zika virus infections have been confirmed in several infants with microcephaly; it is not known how many of the microcephaly cases are associated with Zika virus infection. Studies are under way to investigate the association of Zika virus infection and microcephaly, including the role of other contributory factors (e.g., prior or concurrent infection with other organisms, nutrition, and environment).
Q) Is there any known association between maternal Zika virus infection and other adverse pregnancy outcomes?
The full spectrum outcomes that might be associated with Zika virus infections during pregnancy is unknown and requires further investigation.
Q) Which pregnant women should be tested for Zika virus infection?
Obstetrical providers should obtain a travel history from all pregnant women and use recent travel history to guide decisions about testing. Testing is not indicated for pregnant women without a travel history to an area with Zika virus transmission.
Pregnant women with a history of travel to an area with Zika virus transmission and who report two or more symptoms consistent with Zika virus disease (including acute onset of fever, maculopapular rash, arthralgia or conjunctivitis) during or within two weeks of travel should be tested. In addition, pregnant women with a history of travel to an area with Zika virus transmission and who have ultrasound findings of fetal microcephaly or intracranial calcifications should also be tested for Zika virus infection. Testing should be performed in consultation with state or local health departments.
Q) Who should be offered amniocentesis?
Amniocentesis should be offered to pregnant women with recent travel to an area with Zika virus transmission, reporting2 or more symptoms within two weeks of travel and a positive or inconclusive maternal serum test. For pregnant women with recent travel to an area with Zika virus transmission and ultrasound findings of microcephaly or intracranial calcifications, amniocentesis may also be considered. Consultation with a maternal-fetal medicine specialist should be considered.
Q) Why is amniocentesis offered?
While amniocentesis is a relatively safe test, risk and benefits of amniocentesis should always be considered. An amniocentesis can be used to provide additional clinical information. For example, a positive RT-PCR result on amniotic fluid would be suggestive of intrauterine infection and potentially useful to pregnant women and their healthcare providers to guide decisions about timing of delivery and the level of neonatal care at delivery sites.
Q) When should amniocentesis be performed?
Timing of amniocentesis should be individualized based on the patient’s clinical circumstances. Amniocentesis is not recommended until after 15 weeks of gestation. Amniocentesis performed ≥15 weeks of gestation is associated with lower rates of complications than those performed at earlier gestational ages (≤14 weeks of gestation). However, the exact timing of amniocentesis should be individualized based on the patient’s clinical circumstances. Referral to maternal-fetal medicine or infectious disease specialist with expertise in pregnancy management may be warranted. Risk and benefits of performing the amniocentesis should be discussed with the patient.
Prenatal Diagnosis of MicrocephalyQ) Why is fetal ultrasound recommended?
Fetal ultrasound is generally performed in pregnancies between 18-20 weeks of gestation to assess fetal anatomy as part of routine obstetrical care. Although microcephaly and intracranial calcifications are typically detected during ultrasounds later in pregnancy, these findings might be detected as early as 18-20 weeks gestation. Microcephaly and intracranial abnormalities have been demonstrated in pregnancies with known Zika virus disease. Hence, additional ultrasounds might provide an opportunity to identify findings consistent with fetal Zika virus infection and offer pregnant women the option of amniocentesis to test for Zika virus RNA.
Q) What prenatal ultrasound findings have been observed among infants with confirmed Zika virus infection?
Brain abnormalities reported in infants with laboratory-confirmed congenital Zika infection include microcephaly and disrupted brain growth. Some infants with possible Zika virus infection have been found to have intracranial calcifications and abnormal eye findings. It is not known if Zika virus infection caused any of these abnormalities.
In one report of two infants with Zika virus RNA detected by PT-PCR, brain anomalies detected on ultrasound included corpus callosal and vermian dysgenesis, enlarged cisterna magna, severe unilateral ventriculomegaly, agenesis of the thalami, cataracts, intracranial and intraocular calcifications
Q) How early can microcephaly be diagnosed during pregnancy?
Microcephaly might be detected as early as 18-20 weeks of gestation however, detection by prenatal ultrasound can be challenging at this gestational age due to fetal position and fetal motion artifact. The optimal time to perform ultrasound screening for fetal microcephaly is not known. In the absence of microcephaly, the presence of intracranial calcifications before 22 weeks gestation might suggest a risk for the future development of microcephaly.
Q) How accurately can ultrasound detect microcephaly with maternal Zika virus?
The accuracy of ultrasound to detect microcephaly in the setting of maternal Zika virus is not known and will depend on many factors such as the timing of maternal infection relative to the timing of screening, severity of microcephaly, patient factors (e.g., obesity), gestational age, the equipment used, and the expertise of the person performing the ultrasound. Because the absence of fetal microcephaly and intracranial calcifications on ultrasound at one point in pregnancy does not exclude future microcephaly, serial ultrasounds may be considered. As we get more information specifically related to Zika virus infection and microcephaly, we expect that more specific guidance for women and their healthcare providers will be developed.
Q) If a prenatal ultrasound demonstrates microcephaly, how well does it predict microcephaly in the infant?
The sensitivity of prenatal ultrasound for detection of microcephaly depends on a range of factors (e.g., timing of screening, severity of microcephaly, patient factors). In a study of microcephaly not caused by Zika virus infection, prenatally diagnosed microcephaly correlated with neonatal microcephaly approximately 57% of the time.
Zika virus and Air Ambulance International