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Laboratory testing for Zika virus and dengue virus infections Interim guidance 14 July 2022
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Laboratory testing for Zika virus and dengue virus infections Interim guidance 14 July 2022
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Laboratory testing for Zika virus and denguevirus infections
Interim guidance
14 July 2022
Executive summary
Zika virus (ZIKV) and dengue virus (DENV) remain • Molecular assays are the preferred detection
significant public health threats. ZIKV infection is a cause method but the period of RNA detectability
of microcephaly and other congenital malformations and following infection is limited.
can cause neurological disease in children and adults. • Interpretation of serologic test results remains
Persons infected with DENV are at risk of severe disease challenging because of cross-reactivity and
and death if not managed appropriately. ZIKV and DENV prolonged detection of virus-specific antibodies;
infections cannot be readily distinguished clinically; their utility depends on the patient’s current and
infections need to be differentiated from each other, and prior flavivirus exposures.
from other circulating arboviral and non-arboviral
pathogens, using laboratory tests. This document • Testing for antibodies to ZIKV and DENV should thus
provides revisions to the previous interim guidance be done with careful consideration of
published in 2016 on laboratory testing for ZIKV based on epidemiologic and clinical context.
data and experience gathered during and after the Zika • For pregnant women, the diagnosis of ZIKV should
Public Health Emergency of International Concern always be based on laboratory evidence and testing
(PHEIC) and incorporates current state of knowledge and in these patients should not be limited to a subset
guidance for DENV diagnosis [1,2]. In the absence of of samples, even during outbreaks.
diagnostic randomized control trials to determine • For pregnant women, accurate diagnosis is of
outcomes of comparative testing strategies, particular importance; prolonged detection of RNA
recommendations are based on panel review of the in blood and urine may facilitate. confirmation of
performance data of assays and the experience and ZIKV infection in these patients
observations made within their institutions through
• ZIKV IgM testing in pregnant women should be used
extensive arbovirus testing.
with caution, since a positive test might reflect
Updated key considerations, recommendations and good infection that occurred prior to pregnancy
practices include:
• ZIKV testing for asymptomatic pregnant women
• ZIKV and DENV infections need to be differentiated remains challenging because of unknown optimal
from each other, and from other circulating timing of specimen collection and risks of false
arboviral and non-arboviral pathogens, using positive and false negative results.
laboratory tests. • Only laboratory tests that have undergone
• Laboratory tests performed and interpretation of independent, comprehensive assessment of
results must be guided by the interval between quality, safety and performance should be used for
symptom onset or exposure, and the collection of diagnosing arboviral infections.
specimens. • Any testing for the presence of ZIKV, DENV, and
• WHO recommends the use of whole blood, serum, other pathogens in the differential diagnosis should
or plasma routine diagnostic testing for be performed in appropriately equipped
arboviruses, and urine for ZIKV NAAT testing. laboratories by staff trained in the relevant
technical and safety procedures
-1-
, Laboratory testing for Zika virus and dengue virus infections: interim guidance
1. Introduction epidemiologic surveillance, including detection, tracking,
and control of outbreaks.
1.1 Background Public health and clinical practitioners should be aware of
Zika (ZIKV) and dengue (DENV) viruses are arthropod- locally prevalent pathogens, both to develop appropriate
borne viruses (arboviruses) that are primarily transmitted differential diagnoses and to identify circulating and
by Aedes (Stegomyia) mosquito vectors and are related to emerging flavivirus infections or vaccine programmes that
other flaviviruses including yellow fever, Japanese may confound serologic diagnosis, for example, Japanese
encephalitis and West Nile viruses [3,4]. Sharing common encephalitis in Asia, yellow fever in Africa and South
mosquito vectors and ecology, ZIKV and DENV often America, West Nile virus in North America and Europe, and
circulate in the same geographic region. Infections with tick-borne encephalitis in Asia and Europe [9].
these viruses are frequently asymptomatic. Symptomatic
This document provides revisions to the previous interim
infections are characterized by non-specific clinical
guidance published in 2016 [1] on laboratory testing for
features including fever, rash, malaise, headache,
ZIKV and is based on data and experience gathered during
conjunctivitis, myalgia, and arthralgia. ZIKV infection tends
and after the PHEIC for ZIKV infection and includes the
to be mild and self-limited but rarely can cause more
following updates:
severe disease manifestations including Guillain-Barré
syndrome in adults and children. ZIKV infection in • more information is provided on selection and
pregnant women can cause congenital infection in their interpretation of laboratory diagnostic tests for both
offspring and, in some cases, congenital Zika syndrome ZIKV and DENV as these viruses typically circulate in
(CZS), which includes microcephaly and other congenital the same regions, and cannot be readily
malformations; infection may also result in intrauterine distinguished clinically,
foetal death. Persons infected with DENV are at risk of • reiteration that ZIKV and DENV infections need to be
severe disease and death; secondary infections by other differentiated not only from each other but also from
serotypes increase the risk of developing severe dengue. other locally relevant circulating arboviral and non-
However, evidence-based management of suspected DENV arboviral pathogens, using laboratory tests;
infections has dramatically reduced mortality to <1% [5]. • clarification on selection of specimen types based on data
Of note, the clinical manifestations of acute febrile illness published after the 2016 interim guidance was posted;
and/or rash seen in ZIKV and DENV disease are common to • different testing strategies outlined for pregnant
many infectious and non-infectious aetiologies that need versus non-pregnant patients;
to be considered in the differential diagnosis. In countries
• broadened intervals between symptom onset and
endemic for malaria, for example, it may be advisable to
specimen collection to be considered for molecular
initially test for malaria parasites before testing for
testing for ZIKV in pregnant women where RNA
arboviruses depending on which pathogen is more
detection provides more robust and specific
prevalent at that time [6]
evidence of recent infection;
ZIKV outbreak activity was first documented in the Yap • concession that if specimens collected within 7 days
Main Islands, Federated States of Micronesia, in 2007, are negative by NAAT, IgM testing can be considered
followed by reports of cases in Asia in 2010 [3]. However,
• better delineation of the role and limitations of IgM
the public health impact of ZIKV infection was appreciated
and IgG antibodies for diagnostic use;
anew during the rapid multi-country spread in the Western
• the previous interim guidance encouraged collection
Pacific from 2013-15 and then in the Americas from 2015,
of various specimen types for examination of ZIKV
when concerning ZIKV-associated congenital
and neurological complications, microcephaly, and
neurodevelopmental disorders associated with maternal
sexual transmission; however, those outcomes and
infection during pregnancy were first recognized, as were
modes of transmission have now been confirmed and
increased rates of Guillain-Barré syndrome. In addition,
thus specimen collection should focus on targeted
sexual, congenital and perinatal routes of transmission
diagnostic testing according to established
were identified. Although epidemic ZIKV transmission has
protocols;
decreased substantially in the Americas, low-level endemic
and sporadic transmission continues to occur in some • description of the limitations of testing of
countries within the region and in other parts of the world. asymptomatic pregnant women in the absence of data
In 2019, three autochthonous ZIKV cases occurred in on optimal timing of testing and assays to be used
France [7]. By contrast, DENV outbreak activity continues • removal of text pertaining to the emergency use
to increase, with record numbers of cases reported in Asia assessment and listing (EUAL) as the WHO
and Latin America in 2019, including areas previously Prequalification Team ceased to assess new
impacted by ZIKV [8]. Laboratory testing is critical for applications following the end of the PHEIC for Zika
accurate diagnosis, clinical management, and virus infection.
-2-
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