AAFP's Upcoming Zika Webinar Aims to Help You Prepare

CDC Assesses, Offers Guidance on Urine Testing for the Virus

May 18, 2016 02:00 pm Chris Crawford

This summer, as mosquito populations proliferate and people spend more time outside, family physicians are sure to encounter patients who have questions about mosquito bites and the potential to contract Zika virus disease.

[Man having video chat with doctor on laptop at home]

That's why the AAFP is hosting a members-only webinar from noon to 1 p.m. CDT on May 24 to arm family physicians with the latest information on Zika virus so they can answer patients' questions with evidence-based information. (Editor's Note: The webinar has been archived and is now available to AAFP members.)

Hosted by Nina Ahmad, M.D., medical director of the division of epidemiology for the New York State Department of Health, the webinar is designed to educate members about transmission, symptoms, diagnosis and prevention of Zika virus disease.

"There has not been local transmission of the Zika virus in the continental U.S.," Jennifer Frost, M.D., medical director of the AAFP Health of the Public and Science Division, told AAFP News. "But with increased travel and warmer weather during the summer months, family physicians will be faced with more potential exposures. This webinar will help them to understand what symptoms to look for and how to diagnose the virus."

Story highlights
  • On May 24, the AAFP will host a members-only webinar on Zika virus infection that will review epidemiology, transmission patterns, clinical manifestations, complications and reporting.
  • On May 10, the CDC posted an early-release Morbidity and Mortality Weekly Report (MMWR) that offers guidance on testing urine for Zika virus.
  • The CDC posted another early-release MMWR that reviewed Zika virus testing results from the Florida Department of Health Bureau of Public Health Laboratories and supported urinalysis as the preferred method to identify acute disease.

CDC Offers Guidance for Urine Testing

In related news, the CDC posted an early-release Morbidity and Mortality Weekly Report (MMWR)(www.cdc.gov) May 10 that offers guidance on testing urine to detect Zika virus.

Although diagnostic testing for Zika virus infection can be done using molecular as well as serologic methods, real-time reverse transcription-polymerase chain reaction (rRT-PCR) is the preferred test to identify Zika virus infection because it can be performed rapidly and is highly specific.

"However, in most patients, Zika virus RNA is unlikely to be detected in serum after the first week of illness," said the report. "Recent reports using adaptations of previously published methods suggest that Zika virus RNA can be detected in urine for at least two weeks after onset of symptoms."

The CDC's Trioplex rRT-PCR assay is the only diagnostic tool currently being used (under an Emergency Use Authorization by the FDA) for Zika virus testing of urine. Other laboratory-developed tests need in-house validation to adequately characterize assay performance and meet Clinical Laboratory Improvement Amendments requirements.

The MMWR report said further investigation is needed to determine the sensitivity and utility of Zika virus rRT-PCR assay on urine specimens collected 14 or more days after symptom onset.

"On the basis of the newly available data, the CDC recommends that Zika virus rRT-PCR be performed on urine collected less than 14 days after onset of symptoms in patients with suspected Zika virus disease," the report said.

The agency further recommends that Zika virus rRT-PCR testing of urine be performed in conjunction with serum testing, with a positive result in either specimen type providing evidence of Zika virus infection.

Florida Shares Zika Testing Results

A second early-release MMWR(www.cdc.gov) article posted May 10 compared Zika virus RNA testing of urine, serum and saliva specimens "to determine the most sensitive and efficient testing algorithm for acute Zika virus disease." After evaluation by specimen type and days after symptom onset, results suggested urine testing might be the preferred specimen method to identify acute disease.

According to the MMWR, the Florida Department of Health Bureau of Public Health Laboratories (BPHL) tested specimens from 913 people as of April 20 who met state criteria for Zika virus testing. Among these people, 91 met confirmed or probable Zika virus disease case criteria, and all of these cases were travel-associated.

According to the report, urine specimens were collected from 70 patients with suspected Zika virus disease from zero to 20 days after symptom onset. Of these patients, 93 percent tested positive for Zika virus RNA by rRT-PCR assay, with almost all of these tests being collected within five days of symptom onset. In comparison, only 56 percent of serum specimens collected on the same date tested positive by rRT-PCR.

Of the urine specimens collected after five days from symptom onset, 82 percent were found to be positive by rRT-PCR assay, whereas none of the tests on serum specimens yielded positive results. Also, no cases were exclusively identified by rRT-PCR testing of saliva.

The CDC said in the report that the ability to confirm that an illness is caused by Zika virus and not another flavivirus by detecting Zika virus RNA in a clinical specimen is important, given the limitations in interpreting the results of serology testing in patients who previously have had flavivirus infection or who have been vaccinated against it.

"Among pregnant women, this ability to confirm Zika virus is important because close monitoring during pregnancy is recommended for women with confirmed Zika virus disease," the report said.

AAFP Backs Emergency Funding for Zika Preparation

And on the legislative front, the AAFP joined dozens of medical and health organizations in a May 13 joint letter to members of the Senate(3 page PDF) urging immediate action to provide emergency funding for Zika virus preparedness activities. The letter emphasized the importance of taking action before the mosquito season begins.

"With this funding, federal, state and local public health professionals will be able to pursue virus readiness and response; enhanced laboratory, epidemiology and surveillance capacity in at-risk areas; and surge capacity through rapid response teams to limit potential clusters of Zika virus," said the groups in their letter.

The letter also explained that this supplemental funding would help the CDC and the United States Agency for International Development in their efforts to contain Zika virus in countries in which the virus is endemic and ensure that resources are available for surveillance, vector control and services for affected pregnant women and children.

The previous month, the Academy had signed on to another letter to Congress that urged legislators to provide emergency funding for these Zika virus-related efforts.

Related AAFP News Coverage
CDC Finds Causal Relationship Between Zika Virus, Birth Defects
Agency Also Expands on Sexual Transmission of Virus, Creates Pregnancy Registry


Bracing for Zika Virus Inside the United States
CDC Releases Zika Virus Case Studies


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(May 15, 2016)