Zika Testing and Mosquito Activity

Information updated on Fridays

Philadelphia Zika Testing
Confirmed and Probable Cases: 53
*A revised case definition was implemented on 9/26/2016.
Unspecified flavivirus infections were re-classified as probable Zika cases.


Last Updated (06/16/2017)
Philadelphia Mosquito Activity
Number of traps with Aedes aegypti Mosquitoes: 0
Number of traps with Aedes albopictus Mosquitoes:82


Last Updated (06/16/2017)

Latest Updates to Zika Guidance

  • On Wednesday, May 24, PDPH posted an updated Zika Virus Laboratory Submission Form. See the Diagnostic and Treatment Section.

Health Alerts, Advisories, Notifications, and Updates

Surveillance

Vaccine Information

  • No vaccines are currently available for Zika virus.

Diagnostics and Treatment

Clinical Characteristics

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.

Table 1: Zika Clinical Characteristics
Average Incubation (Range) % with Symptoms Symptoms Outcome
Zika 2–7 days
(2–12 days)
18-25% Mild illness with low-grade fever, maculopapular rash, conjunctivitis, or arthralgia. Other symptoms may include myalgia, headache, or retro-orbital pain. 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

Testing

For symptomatic persons with suspected infections, serum and urine specimens can be tested for Zika using PCR and IgM assays. Testing for Zika is available through the Pennsylvania Department of Health (PADOH) laboratory (Click here for the PADOH laboratory testing form ) and CDC with prior approval by PDPH only. The following commercial laboratories offer both Zika PCR and IgM testing as well: LabCorp, Quest Diagnostics, Viracor, and Bioreference.

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.

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.

Serum:
  • 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.

Urine:
  • 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
    *Note: 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 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.
  • 4-fold change in virus-specific PRNT or IgG titers (dengue and chikungunya) from paired sera collected 2 or more weeks apart


Pregnant Women

At each prenatal care visit, the provider should assess the pregnant patient for possible Zika exposure. Pregnant women who have traveled to areas with active Zika transmission or have another possible exposure (e.g., unprotected sex with a returning traveler) should be screened and tested for Zika infection regardless of whether they became symptomatic. Diagnostic testing will vary by time since illness onset or last exposure date (asymptomatic pregnant patients).

  • 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 will test urine collected after Day 14 and 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. Retesting for Zika virus is recommended for women who initially test negative and have ultrasound evidence of microcephaly, intracranial calcifications or other abnormalities possibly due to Zika. For further information, see CDC’s guidance for clinical management of pregnant women with suspected Zika infections.


Figure 1. CDC Testing Algorithm for Pregnant Women Exposed to Zika


Table 2. CDC Clinical Management of Pregnant Women with Suspected and Confirmed Zika Infections
Interpretation of Laboratory Results* Prenatal Management Postnatal Management
Recent Zika virus infection

Recent flavivirus infection; specific virus cannot be identified
Consider serial ultrasounds every 3–4 weeks to assess fetal anatomy and growth.† Decisions regarding amniocentesis should be individualized for each clinical circumstance.§ Live births: Infant serum and urine collected within 2 days of birth should be tested for Zika virus by rRT-PCR, and for Zika IgM and dengue virus IgM antibodies. If CSF is obtained for other reasons, it can also be tested. Zika virus rRT-PCR and IHC staining of umbilical cord and placenta are recommended.¶ Fetal losses: Zika virus rRT-PCR and IHC staining of fetal tissues are recommended.¶
Presumptive recent Zika virus infection**

Presumptive recent flavivirus infection**
Consider serial ultrasounds every 3–4 weeks to assess fetal anatomy and growth.† Amniocentesis might be considered; decisions should be individualized for each clinical circumstance. Live births: Infant serum and urine collected within 2 days of birth should be tested for Zika virus by rRT-PCR, and for Zika virus IgM and dengue virus IgM antibodies. If CSF is obtained for other reasons, it can also be tested. Zika virus rRT-PCR and IHC staining of umbilical cord and placenta should be considered.¶ Fetal losses: Zika virus rRT-PCR and IHC staining of fetal tissues should be considered.¶
Recent dengue virus infection Clinical management in accordance with existing World Health Organization guidelines.
No evidence of Zika virus or dengue virus infection Prenatal ultrasound to evaluate for fetal abnormalities consistent with congenital Zika virus syndrome.† Fetal abnormalities present: repeat Zika virus rRT-PCR and IgM test; base clinical management on corresponding laboratory results. Fetal abnormalities absent: base obstetric care on the ongoing risk for Zika virus exposure risk to the pregnant woman.
Abbreviations: CSF = cerebrospinal fluid; IgM = immunoglobulin M; IHC = immunohistochemical; PRNT = plaque reduction neutralization test; rRT-PCR = real-time reverse transcription–polymerase chain reaction.
* Refer to the previously published CDC guidance for testing interpretation.
† Fetal abnormalities consistent with congenital Zika virus syndrome include microcephaly, intracranial calcifications, and brain and eye abnormalities.
§ Health care providers should discuss risks and benefits of amniocentesis with their patients. It is not known how sensitive or specific rRT-PCR testing of amniotic fluid is for congenital Zika virus infection, whether a positive result is predictive of a subsequent fetal abnormality, and if it is predictive, what proportion of infants born after infection will have abnormalities.
¶ Refer to CDC pathology guidance for collection and submission of fetal tissues for Zika virus testing for detailed information on recommended specimen types.
** rRT-PCR or PRNT should be performed for positive or equivocal IgM results as indicated. PRNT results that indicate recent flavivirus infection should be interpreted in the context of the currently circulating flaviviruses. Refer to the CDC laboratory guidance for updated testing recommendations. Because of the overlap of symptoms and areas where other viral illnesses are endemic, evaluate for possible dengue or chikungunya virus infection.


Zika-specific testing of serum and urine at the time of birth should be performed for infants with possible congenital Zika infection:

  • Infants with microcephaly or intracranial calcifications born to women exposed to Zika virus while pregnant (i.e., travel or residence in an area with Zika virus transmission, sexual contact with an infected partner)
  • Infants born to mothers with positive or inconclusive test results for Zika virus infection

Thorough clinical evaluation and laboratory testing for infants with possible congenital Zika virus infection are also indicated, including testing to rule out other congenital infections for infants with microcephaly and long-term follow up for infants without microcephaly born to mothers who have positive or inconclusive Zika test results during pregnancy. See CDC’s guidance for congenital Zika infections for more information.


Treatment

  • Patients with Zika should be managed as dengue with acetaminophen recommended for initial treatment.
  • If dengue, which causes hemorrhagic complications, has been ruled out, NSAIDS may be considered to manage fever.

Reporting to PDPH

To arrange for testing and report suspected Zika cases including possible congenital infections, neurologic complications, and Guillain-Barre syndrome post-infection, contact PDPH by calling 215-685-6742 during business hours.

Health Educational Materials

Links and Resources

Guidelines for Management and Control


Zika Virus Guidelines
Prevention for Travelers
Mosquito Bite Prevention for Returning Travelers
  • Advise patients with suspected Zika infections to stay indoors and avoid mosquito bites for the first 7 days of illness to prevent local transmission.
  • During mosquito season in Philadelphia (April to October), encourage travelers returning from areas with Zika outbreaks who are asymptomatic to continue to take steps to avoid mosquitoes especially during the 3 weeks following their return to Philadelphia.
    • use repellent when outdoors
    • wear long sleeves and pants when weather permits
    • remove sources of standing water around their home a few times a week
    • keep screens on doors and windows in good repair
Clinical Guidelines for Zika
Prevention of Sexual Transmission and Family Planning Considerations for Returning Travelers Since sexual transmission of Zika virus is possible and Zika virus may persist in semen longer than blood, providers should counsel individuals who traveled to a country with Zika transmission and their partners on the prevention of sexual transmission. This guidance also extends to conception planning if the patient or their partner has traveled to or resides in a Zika-affected area. Duration of precautions (abstinence, condom use, wait time to attempt conception) will vary depending on which partner traveled and whether s/he developed symptoms (See Table 3 at the bottom of this page).

As part of family planning counseling, healthcare providers should provide information on available strategies to prevent unintended pregnancy, including use of the most effective contraceptive methods that can be used correctly and consistently by the patient. In addition, patients should be counseled that correct and consistent use of condoms reduces the risk for sexually transmitted infections including Zika.


Table 3: Prevention of Sexual Transmission of Zika Virus and Family Planning Considerations (Updated: 11/10/16)
Patient Gender Patient Zika Symptoms/Exposure
(travel to or residence in an affected area)
Patient Pregnancy Status
(females only)
Partner Characteristics
Zika Symptoms/ Exposure (travel to or residence in an affected area) /
and Pregnancy Status
Duration of Precautions
(abstinence/condom use and wait time for conception)
Male
Symptomatic or asymptomatic with exposure to Zika -- Pregnant partner duration of pregnancy
Symptomatic or asymptomatic with exposure to Zika -- Non-pregnant partner regardless of gender 6 months
No symptoms or exposure -- Symptomatic male or asymptomatic male with exposure to Zika 6 months
No symptoms or exposure -- Symptomatic female or asymptomatic female partner with exposure to Zika 8 weeks
Female
Regardless of symptoms or exposure pregnant Symptomatic male or asymptomatic partner (male or female) with exposure to Zika duration of pregnancy
Symptomatic or asymptomatic with exposure to Zika not pregnant No symptoms or exposure 8 weeks
No symptoms or exposure not pregnant Symptomatic male or asymptomatic male with exposure to Zika 6 months
No symptoms or exposure not pregnant Symptomatic female or asymptomatic female with exposure to Zika 8 weeks


Updated: 05/24/2017 5:00pm