TEST UPDATE

zika-mosquito-3.jpgIn 2007 the epidemic potential of Zika virus became apparent, followed by several epidemics in the Pacific Ocean Region including outbreaks in 2013-2014 with thousands of confirmed cases in French Polynesia. In 2015 the first cases of Zika virus infection were confirmed in Brazil, which indicated the beginning of the largest outbreak record with vector-borne transmission. This is now documented to be affecting more than 70 countries worldwide. Although it is still widely believed that most Zika virus infections in humans are asymptomatic or mild with self-limiting clinical manifestations, Zika virus infections can lead to microcephaly and other serious brain abnormalities, major complications, including congenital birth defects, neurologic disorders, and prolonged risk for sexual transmission of this virus.

 

The global risk assessment has not changed. Zika virus continues to spread geographically to areas where effective vectors are present. Healthcare professionals are now faced with a population of children with congenital Zika virus syndrome and a broad spectrum of clinical and radiological presentations with an as yet unknown clinical course. Zika virus is particularly of concern in pregnant women.

How Zika spreads

  • Through mosquito bites
  • From a pregnant woman, even without symptoms, to her unborn child
  • Through sex, and probably blood transfusion

There is no vaccine – protection against bites is the only prevention at the moment.

 

Diagnosis is based on a person’s recent travel history, symptoms and test results. Blood or Urine testing can confirm a Zika infection. Symptoms of Zika are similar to other illnesses through mosquito bites (like dengue and chikungunya).

 

Couples with a partner who lives or has travelled to an area with risk of Zika, especially those who are pregnant or planning to become pregnant should take steps to protect during sex. Zika can stay in semen for months after infection (even without symptoms) and can spread to partners during that time. Symptomatic female partners should wait at least 8 weeks after symptoms started, or 6 months after symptoms started in the male partner. A man infected with Zika can spread the virus during sex with a pregnant women and the virus can pass to the fetus. Condoms must be used every time for vaginal, anal or oral sex.

 

Interpretation of Zika virus test results

Detection of Zika virus RNA in any sample is diagnostic of infection with this virus. However, if Zika virus RNA is not detected in a patient’s samples, this does not exclude previous infection with this virus.

 

Detection of Zika virus Antibodies IgM, with or without Zika virus IgG, in a serum sample from an individual who has had recent symptoms, will usually indicate recent Zika virus infection. Detection of Zika virus Antibodies IgG, with or without IgM, in a serum sample from an individual who has had recent symptoms, will often reflect recent Zika virus infection. This is because Zika virus IgM is frequently not detectable in individuals who have previously had dengue virus infection. Sometimes it is not possible to determine whether a positive Zika virus IgG result (without IgM) is due to recent Zika virus infection, past Zika virus infection, cross-reactivity from another flavivirus infection or non-specific reactivity. In such cases, it is usually appropriate to manage the patient as if they may have had recent Zika virus infection.

 

If Zika virus IgM or IgG antibodies are not detected in a serum sample collected at least 2 weeks after the onset of an acute viral illness featuring fever, rash, arthralgia or conjunctivitis in a pregnant woman, appropriate investigations for alternative causes including parvovirus, rubella, CMV, dengue and chikungunya infections must be carried out, if not already performed. If no firm diagnosis is made, the patient should be individually discussed with a Consultant Virologist, and contact with PHE for further advice considered.

 

If Zika virus antibodies are not detected in a serum sample collected 4 or more weeks* after the last possible travel-associated or sexual exposure, then recent Zika virus infection is highly unlikely. Therefore, pregnant women with negative antibody results for such samples do not require further extra fetal ultrasound follow-up, unless there are additional concerns.

 

Public Health England: Zika virus (ZIKV): clinical and travel guidance, 17 November 2017.

*This period of 4 or more weeks is derived by adding together 14 days, representing the estimated upper limit of the incubation period for Zika virus, and a further 14 days representing a maximum time for the appearance of Zika antibodies after symptom onset (although available evidence indicates that antibodies usually appear much earlier than this).

 

 

Zika Virus RNA by PCR

Code

Sample Reqs

Turnaround

ZIKU

Urine

5-10 days

Special instructions

 

 

Zika Virus Antibodies IgM and IgG

Code

Sample Reqs

Turnaround

ZKAB

B SST/Serum

5-7 days

Special instructions