Pregnant women who feel sick and have visited countries in which the Zika virus is spreading should see a doctor soon and be tested for infection even though the tests are imperfect, federal health officials said on Tuesday.

That advice was at the core of interim Zika-related guidelines for pregnant women issued by the Centers for Disease Control and Prevention. The authors are specialists in emerging diseases and reproductive health.

The guidelines included a “testing algorithm” to show doctors how to proceed with a worried patient who is pregnant and has recently lived in or traveled to an area where the virus is being transmitted.

Infection with the virus has been linked to brain damage and microcephaly — unusually small heads in infants.