Screening

There is currently no need to screen for Zika virus infection in non-pregnant, asymptomatic travellers returning from a country with ongoing transmission.

Pregnant women

The Centers for Disease Control and Prevention (CDC) recommendations for testing symptomatic and asymptomatic pregnant women are detailed below.[166]

Symptomatic pregnant women

  • Testing is recommended in all symptomatic pregnant women with possible Zika virus exposure (i.e., travel to, or residence in, an area with risk for mosquito-borne Zika virus transmission, or sex with a partner who has travelled to or resides in an area with risk for mosquito-borne Zika virus transmission).

  • Concurrent RT-PCR (paired serum and urine specimens) and serological testing (serum) is recommended in pregnant women as soon as possible up to 12 weeks after symptom onset. If RT-PCR is positive, infection is confirmed, although further testing may be required if the IgM result is negative. If RT-PCR and serology are both negative, diagnosis is excluded. If RT-PCR is negative and serology is either positive or equivocal, PRNT is recommended. A PRNT <10 rules out diagnosis.

  • Serological testing may be considered >12 weeks after symptom onset; however, a negative result does not rule out infection during pregnancy as IgM levels decrease over time. A positive result should be interpreted in the context of the known limitations of serological testing.

  • Dengue virus IgM antibody testing is also recommended in symptomatic pregnant women.

Asymptomatic pregnant women

  • Asymptomatic pregnant women with ongoing possible exposure: RT-PCR (serum and urine) is recommended 3 times during pregnancy (e.g., at the initial antenatal care visit, and then at 2 non-consecutive antenatal visits). If the result is positive, infection is confirmed. Additional testing is not recommended in women who have a positive test any time before or during the current pregnancy. IgM testing is no longer routinely recommended.

  • Asymptomatic pregnant women with recent possible exposure but no ongoing possible exposure (e.g., travel or sexual exposure): testing is not routinely recommended but may be considered on a case-by-case basis.

Pregnant women with possible exposure to Zika virus who have a fetus with antenatal ultrasound findings consistent with congenital Zika virus infection should be tested following the same recommendations for symptomatic pregnant women. If amniocentesis is performed as part of routine clinical care, RT-PCR should be performed on amniotic fluid as a positive result may indicate fetal infection. Testing placental and fetal tissues is not routinely recommended, but may be performed in certain situations (e.g., a woman without laboratory-confirmed infection who has a fetus or infant with possible Zika virus-associated abnormalities).[166]

The CDC has produced an algorithm to assist in clinical decision making about testing based on current recommendations:

One study found that most asymptomatic pregnant women who were tested in the US who had travelled to, or moved from, areas with active Zika virus transmission did not have Zika virus infection.[189] A large-scale antenatal Zika screening programme identified that only 0.2% of pregnant women who were at risk of infection from recent travel to a Zika-affected area became infected.[190]

Sexual transmission

At this time, the Centers for Disease Control and Prevention (CDC) does not recommend testing of men for the purpose of assessing risk for sexual transmission.[191]

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