NEW TESTS

Testing for ZIKA Virus (June 2016)

mosquitoZika Virus is transmitted primarily through mosquitos. In most cases, Zika virus infection causes a mild, self-limited illness. Symptoms last for up to one week after being bitten by an infected mosquito. Time from exposure to symptoms is 3–12 days. Around 80% of Zika virus infection cases are likely to go unnoticed. Symptoms of rash, muscle and joint pain, and conjunctivitis typically predominate and usually occur within 2 weeks after travel to a Zika virus affected area. The incubation period is typically between 2 and 7 days.

 

There is now no doubt that Zika virus infection during pregnancy can cause adverse pregnancy and birth outcomes. Reports of sexual transmission, or suspected infection, in symptomatic patients without travel history and other new claims will continue to expand as more and more evidence becomes available about Zika Virus, and key questions relating to risk are addressed. It is estimated that whilst fewer than 1% of women who contract Zika virus during pregnancy go on to have a baby with microcephaly, in as many as 20% of cases, Zika causes other less immediately obvious forms of fetal brain damage.

 

  • Serum and Urine, both, (< 7 days), Urine only (>7 but ≤14 days) are needed for PCR testing.
  • Serum is needed for Antibody testing
  • Other specimen types such as CSF or Amniotic fluid may be considered for PCR testing.
  • Definitive diagnosis of Zika virus can only be made with laboratory testing.



After onset of symptoms diagnosis of Zika virus:


First week (< 7 days) testing by rRT-PCR of both URINE and SERUM is recommended


Second week (>7 but ≤14 days) testing by eRT-PCR of URINE is recommended


Second week (from 7 days) testing for Zika antibodies IgM and IgG (Serum) is recommended

 

DIAGNOSIS

Preliminary diagnosis

  • Clinical features
  • Places and Dates of travel
  • Activities

Laboratory Testing

  • Viral (rRT-PCR) – urine collected ≤14 days of illness onset)*
  • Viral (rRT-PCR) – both serum and urine for early/acute < 7 days after illness onset

A positive ZIKA rRT-PCR result demonstrates current Zika virus infection

Because viraemia decreases over time and recorded dates of illness onset may not be accurate,
a negative rRT-PCR result may not rule out virus infection and IgM antibody testing should be performed.

  • Virus-specific antibodies IgM and IgM – from Day 7

*Urine Better than Blood for Zika Testing CDC says (Medscape 10/05/2016).
Reference Morbidity and Mortality Report (10th May 2016).

 

TestCodeSample TypeTurnaround Time
PCR testing Blood and Urine < 7 days 
Zika Virus RNA by RT-PCR ZIKA B SST/Serum 7-9 days
Zika Virus RNA by RT-PCR ZIKU Urine (2 samples) 7-9 days
PCR and Serology testing > 7 days but ≤14 days
Zika Virus RNA by RT-PCR ZIKU Urine 7-9 days
Zika Antibodies IgM and IgG (Elisa) ZKAB B SST/Serum (provide 2 samples) 7-9 days
Serology testing > 14 days
Zika Antibodies IgM and IgG (Elisa) ZKAB B  SST/Serum 5 days

Because recorded dates of illness onset may not be accurate, a negative rRT-PCR result may not rule out virus infection and IgM antibody testing should be performed.


Zika MapTravel Notes

  • Symptomatic pregnant women, in any trimester, with a positive travel history should undergo testing
  • Asymptomatic pregnant women, in any trimester, with a positive travel history at 2 to 12 weeks should undergo testing
  • Advice to men who have travelled in Zika areas, or who have or had Zika virus, is to use condoms if their partner is pregnant, or who might become pregnant, for 28 days if asymptomatic and 6 months if symptoms develop.
  • All pregnant women should avoid non-essential travel to areas with active Zika transmission


Transmission

Zika virus is transmitted through the bite of an infected Aedes mosquito, which is the same mosquito that transmits dengue, chikungunya and yellow fever.

 

RT-PCR testing for Zika virus is extremely sensitive and specific; however, due to the short period of viremia, samples must be collected within 14 days of onset of symptoms.

 

If samples can be collected within 7 days testing by rRT-PCR of both URINE and SERUM is recommended. If samples can be collected after 7 days but before 14 days testing by rRT-PCR of URINE is recommended. The use of PCR nullify the cross-reactivity issues noted with serologic testing for Zika virus.

 

Because dates of illness onset may not always be accurate, a negative rRT-PCR result may not rule out virus infection and IgM antibody testing should be performed.

 

Serological testing may indicate the presence of anti-Zika virus IgM and IgG antibodies. Caution is needed with serological results as IgM cross-reactivity is possible with similar mosquito vector infections.

 

TestCodeSample TypeTurnaround Time
Chikungunya (Arbo) IgG/IgM
Positive IgG/IgM will reflex to PCR confirmation
CHIK 1ml Serum 2 weeks
Dengue Virus Serology DENG 1ml Serum 1 week
Dengue Fever PCR DPCR A EDTA or B Serum 2 weeks
Yellow Fever Serology YELL 1ml Serum 10 days

In all cases, please provide details of patient’s travel history.


Sexual transmission

There have been reported cases of sexual transmission with the virus spreading to people who have not visited affected countries. It is not known exactly how long Zika virus is present in the semen of men who have been infected, nor is it known how long after exposure Zika virus can be sexually transmitted from a male partner. Men with partners who are pregnant, or who might become pregnant should consider using condoms for 28 days if asymptomatic and 6 months if symptoms develop.


WHO’s advice now expressly states that men and women of reproductive age living in affected areas should consider delaying pregnancy. This advice does not say for how long..


Treatment

Currently, there is no vaccine or treatment for Zika virus infection. It may be several years before a ZIKA vaccine is widely available. 

 

 

Download the Testing for ZIKA Virus Test (June 2016) update sheet here.