At a Glance
Zika Testing and Mosquito Activity
- Philadelphia Zika Testing (last updated November 10, 2017): Confirmed and Probable Cases: 59
*A revised case definition was implemented on 9/26/2016. Unspecified flavivirus infections were re-classified as probable Zika cases.
- Philadelphia Mosquito Activity (last updated November 10, 2017): Number of traps with Aedes aegypti (0) and albopictus mosquitoes (1162)
- On February 28, 2019, CDC updated their travel recommendations. The updated guidance recommends that pregnant women and couples planning to become pregnant within 3 months talk to their healthcare providers to carefully consider the risks and possible consequences of travel to areas with risk of Zika. CDC continues to recommend that pregnant women not travel to any area experiencing a current Zika outbreak. For CDC Zika Travel Information, visit https://wwwnc.cdc.gov/travel/page/zika-travel-information.
- On Tuesday, October 30, 2018, PDPH updated the Zika guidance for preconception counseling and prevention of sexual transmission of Zika for men. See the Guidelines for Management and Control Section.
No vaccines are currently available for Zika virus.
Diagnosis & Management
Zika virus is primarily spread by the bite of infected Aedes spp. mosquitoes. Other less common modes of transmission include maternal-fetal transmission, sexual transmission, transfusion-associated infection or theoretically transplant-associated infection. A summary of clinical characteristics follows.
- Average Incubation (Range): 2-7 days (2-12 days)
- % with Symptoms: 18-25%
- Symptoms: Mild illness with low-grade fever, maculopapular rash, conjunctivitis, or athralgia. Other symptoms may include myalgia, headache, or retro-orbital pain.
- Outcome: Rarely fatal; resolves in <1 week; Infections during pregnancy can result in microcephaly, sensory deficits, fetal loss, or other birth defects; Rare neurologic complications -- Guillain-Barre syndrome, encephalitis, meningitis, and myelitis
Philadelphia-area healthcare providers are encouraged to utilize commercial laboratories when ordering Zika virus testing for exposed, symptomatic persons with health insurance. PDPH will continue to coordinate approval and testing at the Pennsylvania Department of Health (PADOH) Bureau of Laboratories for the following patients regardless of insurance status(Click here for the PADOH laboratory testing form ):
- Uninsured or under-insured symptomatic patients
- Any exposed, pregnant woman with a fetal loss or ultrasound abnormality
- Newborns with possible Zika-related birth defects or those born to mothers with evidence of Zika infection during pregnancy
See our specimen submission guidance for additional information. Contact PDPH at (215) 685-6742 for testing requests and to report suspected Zika cases who have had testing ordered.
For symptomatic patients, it is important for providers to place separate testing orders for other arbovirus testing (dengue and chikungunya). If IgM testing for dengue and chikungunya is indicated, commercial laboratory testing should be pursued. While the PADOH laboratory can conduct PCR testing for dengue and chikungunya, they do not offer dengue and chikungunya IgM testing.
The type of assay(s) that should be performed will depend on the specimen type and time from illness onset to specimen collection.
- Collect at least 6 milliliters (ml) of blood in a blood tube (red top, serum separator tube, tiger top, speckle top, gold top)
- Centrifuge the blood tube within 6 hours of collection and using sterile technique, transfer the serum to a separate, labeled sterile tube (at least 3 ml serum required) Seal the sterile serum tubes with paraffin film. If a centrifuge is not available on site, pack tubes on cold packs and arrange for transport to a laboratory within 6 hours of collection.
- For symptomatic persons, test for Zika, chikungunya, and dengue.
- Day 1 to 3 of illness: Order PCR
- Day 4 to 13 of illness: Order PCR, IgM, & IgG
- Day 14 and after: Order IgM, & IgG
*Note: IgG testing is not available for Zika.
- Collect 3 mL in a sterile container with a tight fitting screw cap and secure with parafilm.
- Day 1 to 14 of illness: Order PCR
*Note: PCR testing of urine is only recommended for Zika. A serum specimen must be submitted with the urine specimen or testing will not be performed.
The following laboratory results can help confirm diagnosis:
- Positive virus-specific PCR
*Note: Negative PCR results do not exclude Zika infection. Additional serum collected on or after day 14 of illness should be submitted for IgM testing.
- Positive virus-specific IgM titer with evidence of virus-specific neutralizing antibodies
- Plaque-reduction neutralization tests (PRNT) that help differentiate flavivirus infections (e.g., Zika, dengue, West Nile, yellow fever, and Japanese encephalitis viruses) are only available through public health laboratories.
- Results of IgM testing may be falsely negative if the specimen is collected during the first week of illness. Consider collecting an additional serum specimen 2 weeks after the initial specimen for testing.
- Positive IgM results in patients who resided in an affected area or had another ongoing exposure should be interpreted with caution. Evidence that the Zika IgM response can be prolonged has been documented, making it difficult to determine when infection was acquired for these patients.
- 4-fold change in virus-specific PRNT or IgG titers (dengue and chikungunya) from paired sera collected 2 or more weeks apart
At each prenatal care visit, the provider should assess the pregnant patient for travel to areas with active Zika transmission or have another possible exposure (e.g., unprotected sex with a returning traveler or partner who resides in an affected area). As of January 1, 2018, Zika testing is no longer recommended for exposed, asymptomatic pregnant women with healthy pregnancies. Zika testing should continue for the following exposed, pregnant women:
- Pregnant women who develop Zika-specific symptoms (mild fever, rash, arthralgia, or conjunctivitis) during or within 2 weeks of a possible Zika exposure
- Exposed, pregnant women (symptomatic and asymptomatic) who have a fetal loss or prenatal ultrasound findings consistent with congenital Zika virus syndrome (i.e., intracranial calcifications, microcephaly)
As of January 1, 2018, Zika testing is no longer recommended for exposed, asymptomatic pregnant women with healthy pregnancies. Zika testing should continue for the following exposed, pregnant women:
- Day 1 to 13: serum and urine rRT-PCR testing
- Negative PCR results do not exclude Zika infection. Serum collected on or after day 14 of illness or following exposure (asymptomatic pregnant women) should be submitted for IgM testing.
- Day 14 to Week 12: serum IgM testing
- If IgM positive, PCR testing will be performed and if PCR negative, PRNT testing will follow.
Note: For pregnant exposed women, the PADOH laboratory is performing PCR and IgM testing on all serum specimens regardless of timing of specimen collection.
Contact PDPH at (215) 685-6742 for testing requests after the 12-week time frame. For more information, see the CDC testing algorithm for pregnant women exposed to Zika.
For any pregnant woman who has a positive or inconclusive Zika testing result, serial fetal ultrasounds to detect microcephaly, intracranial calcifications, or other abnormalities related to Zika are recommended along with consideration of amniocentesis for Zika testing. For further information, see CDC’s guidance for clinical management of pregnant women with suspected Zika infections.
For Healthcare Providers:
There are no healthcare provider resources available for Zika.
For Patients and Community Members:
PDPH Zika and Pregnancy Brochure for Obstetrician Waiting Rooms
PDPH - Returning from a Zika Area Poster
PDPH - Traveling to a Zika Area Poster