CDC Clarifies Diagnostic Testing for Individuals Who Could Have Either Dengue or Zika

By Will Boggs MD

June 21, 2019

NEW YORK (Reuters Health) - Nucleic-acid-amplification tests (NAATs) should be used to differentiate dengue from Zika virus infection in most patients with clinical illnesses compatible with either infection, according to a new report from the Centers for Disease Control and Prevention (CDC).

"Because both dengue and Zika viruses are transmitted by Aedes aegypti mosquitos in many regions of the tropics, physicians managing patients returning from the tropics with fever, headache, myalgia, and/or rash should order parallel diagnostic testing for both dengue and Zika virus," Dr. Tyler M. Sharp from CDC's National Center for Emerging and Zoonotic Infectious Diseases, in Atlanta, told Reuters Health by email.

Clinical manifestations of dengue and Zika infection are virtually indistinguishable, and antibody testing is complicated by cross-reactivity that might preclude conclusive determination of which virus is responsible for the current infection.

Dr. Sharp and colleagues update CDC's diagnostic-testing guidance for patients, including pregnant women, with illness clinically compatible with dengue or Zika virus disease who reside in or recently traveled to an area where there is risk for infection with both viruses. The complete review and recommendations appear in the June 14 Morbidity and Mortality Weekly Report.

For symptomatic nonpregnant individuals, dengue and Zika virus NAATs should be performed on serum collected within the first seven days of symptom onset, the authors say.

Dengue and Zika virus IgM antibody testing should be performed on NAAT-negative serum specimens or serum collected more than seven days after symptom onset.

For symptomatic pregnant women, serum and urine specimens should be collected as soon as possible within 12 weeks of symptom onset and be evaluated using dengue and Zika virus NAATs and IgM antibody testing.

Positive IgM antibody results in the face of negative NAAT results should be confirmed by neutralizing antibody tests when clinically or epidemiologically indicated, including for all pregnant women.

Appropriate management to monitor and treat shock and hemorrhage is indicated for patients with clinically suspected dengue, and women with laboratory evidence of possible Zika virus infection during pregnancy and their infants should be evaluated and managed for possible adverse outcomes.

Both diseases are nationally notifiable conditions and should be reported to public health authorities.

"Very good molecular tests are currently available to diagnose and differentiate dengue and Zika virus infection in acutely ill patients, and such tests often provide diagnostic confirmation of infection through the first week after illness onset," Dr. Sharp said. "Serologic diagnostic tests for both Zika and dengue are now more widely available than years past, but there are still challenges in differentiating infection with dengue versus Zika virus with these tests."

Dr. Marie Louise Landry, director of the clinical virology lab at Yale New Haven Hospital, in Connecticut, told Reuters Health by email, "For Zika virus, a positive PCR is the most reliable diagnostic test. Providers and patients should be aware that IgM antibody, the more commonly ordered test, is prone to false-positive results and should not be accepted as the final answer."

"Zika IgM-positive sera should be retested using the more specific plaque-reduction-neutralization test (PRNT), which utilizes live virus and is done at CDC," she said.

SOURCE: https://bit.ly/2XkM2OZ

MMWR Morb Mortal Wkly Rep 2019.

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