Testing for ZIKA Virus (June 2016)
Zika 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).
| Test |
Code |
Sample Type |
Turnaround Time |
| PCR
testing Blood and Urine < 7 days |
| Zika Virus RNA by RT-PCR |
ZIKA |
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.
|
Travel 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.
| Test |
Code |
Sample Type |
Turnaround 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.