Zika Virus - PDF Document
Zika Virus
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TEST UPDATE: MAY 2016 Zika Virus 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. DIAGNOSIS Preliminary diagnosis • Clinical features • Places and Dates of travel • Activities • Serum is needed for antibody testing. • Serum, EDTA whole blood or Urine are needed for PCR testing. • Other specimen types such as CSF or Amniotic fluid may be considered for PCR testing. • The definitive diagnosis of Zika virus infection can only be made on the basis of laboratory testing. Laboratory Testing • Viral (RNA) – early/acute up to Day 7 (urine up to Day 10) • Virus-specific IgM and IgM – after Day 7 During the first week after onset of symptoms, Zika virus disease can often be diagnosed by performing reverse-transcriptase polymerase chain reaction (RT-PCR). Test information TEST CODE SAMPLE TYPE TURNAROUND TIME PCR testing before first seven days Zika Virus RNA by RT-PCR ZIKA A EDTA or B SST/Serum or Urine 7– 9 days Reported as Detected/Undetected Antibody testing after seven days Zika Antibodies IgM and IgG (Elisa) ZKAB B SST/Serum 5 days Reported as negative Reported as borderline Reported as positive Ratio < 0.8 negative Ratio 0.8 to < 1.1 borderline Ratio > 1.1 positive
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. 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 7 days of onset of symptoms. If the specimen can be collected within 7 days of illness onset, PCR testing is indicated. The use of PCR nullify the cross- reactivity issues noted with serologic testing for Zika. Serological tests 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 information TEST CODE SAMPLE TYPE TURNAROUND TIME Chikungunya (Arbo) IgG/IgM CHIK 1ml Serum 2 weeks Positive IgG/IgM will reflex, to confirmation by PCR Dengue Virus Serology DENG 1ml Serum 1 week Dengue Fever PCR DPCR A EDTA or B Serum 2 weeks 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. TREATMENT Currently, there is no vaccine or treatment for Zika virus infection, although Zika vaccine trials will likely start in September 2016. For further information, please contact: Annette Wilkinson, The Doctors Laboratory, 60 Whitfield Street, London W1T 4EU Tel: +44 (0)20 7307 7373 E-mail: tdl@tdlpathology.com Website: www.tdlpathology.com The Doctors Laboratory Ltd is a member of the Sonic Healthcare Ltd group of companies. Registered office: 60 Whitfield Street, London W1T 4EU. Registered in England No. 2201998. TAP3135B/10-05-16/V5
