The shifting landscape of Zika virus laboratory testing during the rapidly changing epidemic

Transcription

1 The shifting landscape of Zika virus laboratory testing during the rapidly changing epidemic The 68th Annual Institute of the California Association of Public Health Laboratory Directors (CAPHLD) November 7, 2017 Sharon Messenger

2 Heightened concerns about exotic arboviruses Dengue spread in the Americas... then Chikungunya CDPHVRDL was in a routine mode to bring on new tests in response to the movement of exotic arboviruses to the Americas. then Zika

3 Zika Virus 1 st isolated from a sentinel Rhesus macaque Zika Forest in Uganda in 1947 Zika virus is a mosquitoborne flavivirus similar to dengue, yellow fever, West Nile, and Japanese encephalitis viruses Like dengue and chikungunya, Zika isolated from Aedes mosquitoes

4 Sixteen Zika virus infections reported in humans before the 1 st outbreak on a Pacific island in 2007 Year Reported Location Age, Sex Description 1954 Nigeria 10 yo F Fever and headache 1956 Nigeria 34 yo M Experimentally induced. Residing in Nigeria for 4 ½ months before inoculation. Fever and headache 1964 Uganda 28 yo M Residing in Uganda for 2 ½ months before illness. Headache, rash, and fever 1968 Nigeria 10 mo 2 ½ yo 3 yo 1979 Nigeria 2 ½ yo M 10 yo M No clinical details available. Fever, headache, and body pains. 40% persons tested had neutralizing antibodies to Zika virus (more frequently in younger people), demonstrating high prevalence of immunity in Nigeria. Unreported cases likely misdiagnosed as malaria Portugal? yo M Arbovirus laboratory worker vaccinated against yellow fever 2 months prior. Chills, fever, sweating, retroorbital pain, and pain in back of neck and in joints Indonesia 7 cases, 1232 yo 7 cases in hospitalized patients. All cases had fever; None had rash. Infection occurred ; case published 1964 Blood specimens for the 2 isolates were collected in July 1971 and May 1975; cases published in 1979 Cases occurred in 1977 and 1978; published 1981 from Kindhauser, MK et al Bull World Health Organ 2016;94: C

5 Zika Spreads to Pacific Islands 2007: First major outbreak of Zika on the island of Yap 185 suspect, probable and confirmed cases (~900 estimated cases) : Outbreak in French Polynesia 30,000 estimated cases; 74 with severe neurologic symptoms 2014: Cases reported from New Caledonia, Cook Islands, Easter Island Easter Island

6 Zika virus Infections Generally mild febrile rash illness lasting 27 days 4/5 people infected are asymptomatic Symptoms most commonly reported: Fever Maculopapular skin rash Conjunctivitis Muscle and joint pain Malaise Headache Rarely severe or fatal illness Symptom Chikungunya Dengue Zika Fever 85% 92% 61% Joint Pain 83% 55% 63% Rash 53% 50% 90% Conjunctivitis 0.4% 3% 36% Myalgia 64% 68% 28% Hospitalization 11% 32% 1% Data courtesy of Dr. Charsey Porse (CDPH)

7 November 2015

8 Geographical Distribution, Americas 2015 March 2015: Brazil notifies WHO of reports of an illness characterized by skin rash in northeastern states. States with laboratoryconfirmed cases Zika virus disease, Brazil, 2015 May 2015: Brazil s National Reference Laboratory confirms, by PCR, Zika virus circulation in the country. This is the first report of locally acquired Zika disease in the Americas. July 2015: Brazil reports laboratoryconfirmed Zika cases in twelve states. November 2015: Brazil reports 141 suspected cases of microcephaly in Pernambuco state. Brazil declares a national public health emergency as cases of suspected microcephaly continue to increase.

9 Microcephaly Definition: Head circumference at birth <2 standard deviations below mean for gestational age and sex Outcomes: Range from normal to severe, including death Can include seizures, visual or hearing deficits Correlate with severity of microcephaly Causes: Congenital infection: e.g. syphilis, rubella, toxoplasmosis Genetic disorders and inherited mutations Other brain injury: hypoxia, drugs, toxins, FAS Epidemiology: 2 12/10,000 live births in US

10 Microcephaly More than 4,700 suspected cases of microcephaly were reported from mid2015 through January 2016 NY Times. Short Answers to Hard Questions about Zika Virus. February 24, 2016.

11 Zika Virus is a Cause of Microcephaly NEJM. April 13, 2016

12 Cell Stem Cell May 5;18(5):

13 345 pregnant women with rash enrolled 9/152/ (53%) positive for ZIKV in blood, urine, or both Outcomes tracked for 125 ZIKVaffected & 61 ZIKVunaffected pregnancies Rates of fetal death 7% in both groups Overall adverse outcomes: 46% in ZIKVpositive women vs 11.5% in ZIKVnegative women 42% of live infants born to ZIKVpositive women had grossly abnormal clinical or brain imaging findings Adverse outcomes were noted regardless of the trimester during which the women were infected with ZIKV Brasil P et al. NEJM DOI: /NEJMoa

14 Microcephaly and Zika U.S. Zika Pregnancy Registry (USZPR): 2,549 pregnancies with lab evidence of possible recent Zika virus infection Zikaassociated birth defects detected: included brain abnormality or microcephaly, neural tube defect, eye abnormality, CNS dysfunction 1 in 20 completed pregnancies had Zikaassociated birth defect 1 in 12 if exposed in first trimester and confirmed by NAT Among completed pregnancies with confirmed (NAT) Zika infection identified in each trimester, the percentage of fetuses or infants with possible Zikaassociated birth defects was: 1 st trimester 8% 2 nd trimester 5% 3 rd trimester 4% Overall 5%

15 Guillain Barré Syndrome (GBS) Autoimmune neurologic disease causing weakness and/or paralysis Outcomes: Respiratory weakness needing ventilatory support in 10 30% Autonomic dysfunction in 70%; can lead to sudden death Causes include: Viral infections, such as HIV/AIDS, herpes, respiratory infections, mononucleosis, and flaviviruses Bacterial infections Hodgkin disease, a malignant disease of the lymphatic system Systemic lupus erythromatosus Epidemiology: 1 2 cases/100,000 per year worldwide Surveillance is difficult GBS associated with WNV and JEV Pluta et al. JAMA. 2011;305(3):319

16 GBS and Zika French Polynesia Oehler et al. 2014: 1st case report of GBS following ZIKV infection Retrospectively, 42 cases diagnosed with GBS (20x increase) GBS cases significantly more likely to have evidence of recent Zika infection than matched controls GBS can occur after asymptomatic Zika virus infection Patients with GBS and Zika may be have axonal type of GBS, rapid plateau, lasting deficits Rate of GBS after Zika may be 0.24/1000 cases Similar to estimated rate for Campylobacter infection The Lancet Vol 387 April 9, 2016

17 Figure CaoLormeau, et al: Weekly cases of suspected Zika virus infections and GuillainBarré syndrome in French Polynesia between October, 2013, and April, 2014

18 dos Santos, T et al., NEJM 375;16 October 20, 2016

19 from dos Santos, et al., NEJM 375;16 October 20, 2016

20 Has Zika evolved increased virulence??? Since the link between ZIKV infection and microcephaly was solidified, numerous investigations in cell culture, clinical materials, animal models have provided mounting evidence that ZIKV targets neuronal progenitor cells (NPCs) leading to an array of neurological complications, including microcephaly. Human seroprevalence studies (1950s to present) show longstanding circulation of ZIKV in Africa and SE Asia...yet similar widescale severe disease associated with ZIKV infections was not documented. Some retrospective studies uncovered previously unrecognized neurologic cases associated with ZIKV outbreaks, but not to a comparable degree observed in the Americas. Did the virus evolve increased pathogenicity as it spread to the Pacific and then to the Americas?

21 Comparative genetic approaches begin to shed light on ZIKV virulence from from Haddow et al Genetic characterization of Zika virus strains: Geographic expansion of the Asian lineage. Vol 6(2):e1477. Most early investigations on ZIKV pathogenicity were based on experiments using MR 766 strain.

22 The recognition that the Asian lineage appeared to be associated with greater congenital and neurological disorders led to question whether the Asian lineage was more virulent. Need to address questions of virulence in a comparative framework Numerous studies using African strains (primarily MR 766) show this strain is capable of causing the same or worse damage. MR 766 is highly passaged and has accumulated mutations and deletions not found in nature, and may not be valid. Study using Asian strain from Puerto Rico (Hanners et al., 2016) found reduced toxicity and long term persistence in human neural progenitor cells (NPCs) consistent with clinical manifestations.

23 Cell Reports 15, , June 14, 2016

24 The recognition that the Asian lineage is associated with congenital and neurological disorders led to question whether the Asian lineage was more virulent. Numerous studies using African strains (primarily MR 766) show they are capable of causing the same or worse damage. MR 766 is highly passaged and has accumulated mutations and deletions not found in nature, and may not be valid. Study using Asian strain from Puerto Rico (Hanners et al., 2016) found reduced toxicity and long term persistence in human NPCs consistent with clinical manifestations. Simonin et al. compared African and Asian strains Compared African (CAR 1989) and Asian (French Polynesia 2013) strains African ZIKV strains consistently displayed: higher infectivity higher replication rate triggered more defects in proliferation increased apoptosis stronger induction of antiviral response General conclusion, African ZIKV strains infected more cells, replicated to higher titers, and more likely to induce early cell death. Milder Asian ZIKV strains could be consistent with more persistent infections. Is it possible that infection with more virulent Africanlineage ZIKV may lead to early termination of pregnancy?

25 from The Lancet Vol 389 April 22, 2017 Is the lack of reported microcephaly in Africa a surveillance artifact? GuineaBissau, 2016 April June 2016, 6 infants born with microcephaly after possible exposure to ZIKV September 2016, adult cases were confirmed to ZIKV infections with an African lineage November 2016, 3 of the infants exposed to ZIKV or Chik Lack of resources to accurately detect and characterize outbreaks In ZIKVendemic areas, infections may occur at far lower levels such that microcephaly cases are not significantly higher than background More people may be infected before reproductive age so that fewer exposures occur during pregnancy The Africanlineage ZIKV may be so destructive that pregnancy loss may be occurring early on

26 3 contemporary strains ( ) compared to ancestral Asian strain from Cambodia (2010) Contemporary strains more neurovirulent than CAM/2010 in neonatal mice VEN/2016 & CAM/2010 tested in embryonic mouse model VEN/2016infected mice developed microcephalic brains; CAM/2010 caused less severe symptoms VEN/2016 enhanced replication, increased apoptosis, loss of neurons (i.e., more virulent) Used reverse genetics to construct mutant viruses containing different aa changes S139N showed greatest neurovirulence Estimated that S139N emerged in 2013 (French Polynesia outbreak)

27 Why now? Why did ZIKV suddenly spread after circulating quietly in Africa and SE Asia for decades?

28 Asian ZIKV strains tested: FSS13025 (2010) GZ01 (2016) Mice infected with GZ01 exhibited higher levels of NS1 protein in blood Mosquitoes biting GZ01infected mice had higher infection prevalence Hypothesized that NS1 antigenaemia could be responsible for higher mosquito infectivity Neutralization of NS1 decreased prevalence of mosquito infections Ectopically expressed NS1 enhances infectivity of FSS13025

29 Single amino acid replacement shown to affect infectivity Viruses collected prior to 2012 had alanine at residue 188 of NS1 All isolates collected after 2013 exhibited the alaninetovaline substitution Mutating residue 188 in FSS13025 substantially increases secretion of NS1 AA substitution enhanced transmission of ZIKV from mouse to mosquito

30 Haddow, AD et al Genetic Characterization of Zika Virus Strains: Geographic Expansion of the Asian Lineage Gatherer, D & Kohl, A Zika virus: a previously slow pandemic spreads rapidly through the Americas Zhu, Z et al., Comparative genomic analysis of preepidemic and epidemic Zika virus strains for virological factors potentially associated with the rapidly expanding epidemic Liang, D et al Insights into intercontinental spread of Zika virus Faria, NR et al Zika virus in the Americas: Early epidemiological and genetic findings Naccache, SN et al Distinct Zika Virus Lineage in Salvador, Bahia, Brazil Ayllón, T. et al Early Evidence for Zika Virus Circulation among Aedes aegypti Mosquitoes, Rio de Janeiro, Brazil Faria, NR et al Establishment and cryptic transmission of Zika virus in Brazil and the Americas Metsky, HC et al Zika virus evolution and spread in the Americas Grubaugh, ND et al Genomic epidemiology reveals multiple introductions of Zika virus into the United States

31 Zika s spread to the Americas from Gatherer & Kohl from Faria et al from Metsky et al Largescale genomic studies have refined the timelines and trajectories of ZIKV spread: ZIKV circulating throughout the Americas may have originated from French Polynesia outbreak ZIKV present in NE Brazil by Feb 2014 (late 2013early 2014) Cryptic spread from NE Brazil to South and Central America and the Caribbean before detection Strong association between climactic suitability for Aedes and reported weekly cases estimated spread of viral lineages to new geographic areas occurred during periods of climactic suitability for vector transmission

32 How and when ZIKV arose in Florida from Grubaugh, ND et al ZIKV introduced into FL at least 4 times (possibly as many as 40!) Likely appeared in FL several months before detected Most likely linked to air travel & cruise ships to Miami from the Caribbean

33 Take home messages from phylogenomic studies from Worobey, M. 1 5 J U N E VO L N AT U R E Genetic analyses from several reports concur that ZIKV was introduced to multiple regions of the Americas months before earliest detections by traditional surveillance systems. Laboratorybased (molecular) surveillance is critical to understanding the ecology, evolution and epidemiology of mosquitoborne diseases that may cocirculate and are associated with similar clinical disease.

34 Laboratory Diagnostic Testing for Zika Virus What we knew then... Studies from previous outbreaks of Zika Virus were basis for diagnostic testing guidance Outbreak (Study Reference) Year Study size: # cases lab tested # PCR()/ tested % PCR () # IgM/ tested % IgM PRNT ZIKA > 4X Yap Island (Lanciotti, 2008) French Polynesia (Musso, 2015) New Caledonia (Gourinat, 2015) Easter Island (Tognarelli, 2016) Pernambuco, Brazil (Pessoa, 2016) / % 108/ % 49/ /748 serum 182/319 saliva /6 serum 6/6 urine 28.1% 57.1% 66.7% 100% / % / % Consistently, mean time point of illness to detect Zika virus RNA by RTPCR = 3.5 days

35 What we knew then... Acute dengue vs Zika virus infection 10 8 Viraemia 10 3 IgM?? IgG 80 Zika Dengue modified from Guzman, M. G. et al. Dengue: A continuing global threat. Nature Reviews Microbiology 8, S7 S16 (2010) Zika viraemia is low and of short duration Viral loads <3.5 X 10 3 viral particles/ml compared to ~ for dengue and chikungunya (Lanciotti et al., 2008) Virus is often no longer detectable in serum at or shortly after symptom onset Most detections of Zika virus by RTPCR in serum: <3 days of illness onset Zikaspecific IgM can appear later in course of infection Samples collected <7 days after onset can be falsely negative Zika virus IgM may persist as long as dengue virus IgM (~12 weeks) little data Flavivirusspecific antibodies (IgM & IgG) crossreact requiring confirmation No good tests available to diagnose acute Zika virus disease

36 from Lanciotti et al EID 14(8):12329 Patient Days post onset ZIKV DEN1 DEN2 DEN3 DEN4 JEV YFV WNV SLEV MVEV 822a 822b a 830b a 849b a 862b a 817b a 833b a 844b a 955b 1 14 Primary: No previous flavivirus exposure Secondary: Previous flavivirus exposure Original Antigenic Sin: Predicted problems with confirmatory PRNT Neutralization studies (PRNT) illustrate complexity of the immune response in primary versus secondary flavivirus exposures

37 What we learned in Transmission dynamics complicated Mosquito/ Travel Sexual Congenital Blood transfusion

38 Mounting studies indicated ZIKV can persist in semen for months Atkinson et al ZIKV detected in 167 days

39 Sexual Transmission

40 FDA Guidance on Zika and Blood Banks Revised Recommendations for Reducing the Risk of Zika Virus Transmission by Blood and Blood Components issued Aug 2016 Screen blood products for Zika virus using investigational individual donor nucleic acid test (IDNAT) Use pathogen reduction technology for platelets and plasma Discontinue donor screening questions If donor tests positive for Zika virus: Defer for 120 days Quarantine all blood products collected in prior 120 days

41 What we learned in CDC laboratory testing guidance updates Initial CDC Lab Guidance Jan Jan Feb Mar Apr May Jun Jul Aug Sep 2017 Initial testing guidance released for congenital infections in infants Zika & dengue IgM & RTPCR Updated lab guidance to add testing of asymptomatic pregnant women Zika IgM only >212 weeks return of travel Urine may be a better sample type for RTPCR testing Recognition that Zika viral RNA persists in urine longer than in serum Urine PCR recommended <14 days of symptom onset Revision of PRNT interpretation: traditional use of >4X comparative titers not recommended PRNT titers are measured as present or absent Confirmed or probable Zika virus infection requires Zika Ab neut POS/dengue Ab neut NEG Expand RTPCR testing Increase emphasis on PCR testing of urine and serum If IgM is positive or equivocal, reflex to PCR for pregnant women Whole blood may be preferable to serum & possibly urine for RTPCR Encourage submission of whole blood PLUS urine and serum

42 Clinical Sensitivity of RTPCR on Serum vs Urine Detection of Zika virus RNA in blood vs urine specimens from Gourinat et al EID 21 (1):8486 from Bingham et al. 2016

43 What we learned in CDC laboratory testing guidance updates Initial CDC Lab Guidance Jan Jan Feb Mar Apr May Jun Jul Aug Sep 2017 Initial testing guidance released for congenital infections in infants Zika & dengue IgM & RTPCR Updated guidance to add testing of asymptomatic pregnant women Zika IgM only >212 weeks return of travel Urine may be a better sample type for RTPCR testing Recognition that Zika viral RNA persists in urine longer than in serum Urine PCR recommended <14 days of symptom onset Revision of PRNT interpretation: traditional use of >4X comparative titers not recommended PRNT titers are measured as present or absent Confirmed or probable Zika virus infection requires Zika Ab neut POS/dengue Ab neut NEG Expand RTPCR testing Increase emphasis on PCR testing of urine and serum If IgM is positive or equivocal, reflex to PCR for pregnant women Whole blood may be preferable to serum & possibly urine for RTPCR Encourage submission of whole blood PLUS urine and serum

44 Clinical Sensitivity of RTPCR on Serum vs Urine Testing at VRDL Zika probable and confirmed cases : DPO Serum Zika IgM Serum Trioplex (ZIKV) Urine Trioplex (ZIKV) 0 5/9 56% 7/10 70% 3/3 100% 1 6/15 40% 10/14 71% 3/4 75% 2 8/17 47% 10/16 63% 11/13 85% 3 10/28 36% 21/27 78% 19/19 100% 4 12/19 63% 11/20 55% 12/12 100% 5 18/25 72% 9/22 41% 11/12 92% 6 7/9 78% 4/9 44% 5/5 100% 7 5/8 63% 3/6 50% 6/6 100% ALL 71/130 55% 75/124 60% 70/74 96% Test # positive % positive IgM 156/ % Serum PCR 76/149 51% Urine PCR 156/ %

45 Viral RNA Persistence in different sample types Prior to 2015, estimated persistence of ZIKV RNA in serum <7 days PazBailey et al Enhanced clinical surveillance study in Puerto Rico Time (days) to loss of ZIKV RNA Median 14d 95% 54d Median 8d 95% 39d Median 34d 95% 81d ZIKV RNA detected in serum: 815d 1630d >60d Five pregnant women were included in study. 3 of 5 had detectable RNA in serum 46d post onset

46 Viral RNA persistence in pregnant women Prolonged detection of ZIKV RNA in pregnant women Suy et al N=1 symptomatic pregnant woman Serum PCR 18d to 107d post onset Amniotic fluid PCR(), but other tissues (urine, cervix, vaginal swab) PCR() Bocanegra et al N=1 symptomatic pregnant woman Serum 15d post onset ZIKV IgM/IgG Driggers et al N=1 symptomatic pregnant woman Serum 4 weeks and 10 weeks post onset ZIKV 4 weeks MeanyDelman et al N=5 4 symptomatic women: PCR up to 46d post onset 1 asymptomatic woman: PCR up to 53d postexposure Pacheco et al Among 326 pregnant women who were PCR, Mean # of days from onset to sample collection was 2.6 (median, 2.0; range, 0 to 21) 10 of 326 (3%) were collected more than 7 days after symptom onset Schaub et al N=8 (6 symptomatic, 2 asymptomatic); all had fetal anomalies 6 symptomatic women: blood PCR between 1026 weeks gestation 2 asymptomatic women: blood PCR (both PCR amniotic fluid) All urine samples negative by PCR St. George et al N=75 total cases (6 pregnant women) Mean # of days from onset to sample collection was 10.4 (range, 0 to 53) Six serum samples 16, 17, 25, 46, 53 days were from pregnant women

47 What we learned in CDC laboratory testing guidance updates Initial CDC Lab Guidance Jan Jan Feb Mar Apr May Jun Jul Aug Sep 2017 Initial testing guidance released for congenital infections in infants Zika & dengue IgM & RTPCR Updated guidance to add testing of asymptomatic pregnant women Zika IgM only >212 weeks return of travel Urine may be a better sample type for RTPCR testing Recognition that Zika viral RNA persists in urine longer than in serum Urine PCR recommended <14 days of symptom onset Revision of PRNT interpretation: traditional use of >4X comparative titers not recommended PRNT titers are measured as present or absent Confirmed or probable Zika virus infection requires Zika Ab neut POS/dengue Ab neut NEG Expand RTPCR testing Increase emphasis on PCR testing of urine and serum If IgM is positive or equivocal, reflex to PCR for pregnant women Whole blood may be preferable to serum & possibly urine for RTPCR Encourage submission of whole blood PLUS urine and serum

48 Viral RNA in whole blood and saliva ZIKV detected in whole 91 days from Murray et al Lustig et al detected ZIKV in whole blood up to 58 days Mansuy et al Median duration of ZIKV = 22 (range ) days in whole blood and 10 (range 7 37) days in plasma from Musso et al from CDC EUA Trioplex Barzon et al Detected ZIKV in saliva up to 29 days

49 What we learned in CDC laboratory testing guidance updates Initial CDC Lab Guidance Jan Jan Feb Mar Apr May Jun Jul Aug Sep 2017 Initial testing guidance released for congenital infections in infants Zika & dengue IgM & RTPCR Updated guidance to add testing of asymptomatic pregnant women Zika IgM only >212 weeks return of travel Urine may be a better sample type for RTPCR testing Recognition that Zika viral RNA persists in urine longer than in serum Urine PCR recommended <14 days of symptom onset Revision of PRNT interpretation: traditional use of >4X comparative titers not recommended PRNT titers are measured as present or absent Confirmed or probable Zika virus infection requires Zika Ab neut POS/dengue Ab neut NEG Expand RTPCR testing Increase emphasis on PCR testing of urine and serum If IgM is positive or equivocal, reflex to PCR for pregnant women Whole blood may be preferable to serum & possibly urine for RTPCR Encourage submission of whole blood PLUS urine and serum

50 Detection of prolonged ZIKV IgM ZIKV IgM typically detectable within 2 weeks post onset ZIKV IgM thought to persist as long as dengue virus IgM (~12 weeks) PazBailey et al IgM detected in 140/143 (97.9%) of participants days 07 days 815 > 60 days Prolonged ZIKV IgM may make it difficult to determine timing of infection...median time to 1st negative Zika virus IgM ~ 4 months (122 days [range 8210 days]) Similar to other flaviviruses: Dengue virus: IgM persists for ~6 months (179 days [95% CI, 155 to 215 days]) ; WNV: ~50% of WNV cases are IgM >1 yr

51 What we learned in CDC laboratory testing guidance updates 2016 Jan 2016 Feb Mar Apr May Jun Jul Aug Sep July 2017 Symptomatic pregnant women NAT testing to 12 weeks

52 What we learned in CDC laboratory testing guidance updates 2016 Jan 2016 Feb Mar Apr May Jun Jul Aug Sep July 2017 Asymptomatic pregnant women Without ongoing exposure: No routine testing With ongoing exposure: NAT testing only

53 Why CDPH guidance did not change... It was still unclear what might happen in Mexico in 2017 By the end of 2016 season, ZIKV had not yet peaked in Mexico While IgM may persist for months, majority of cases had single trips to ZIKV endemic areas. An IgM detection more easily interpreted and could be significant While IgM & PRNT testing can lack specificity, among 374 IgM sera VRDL, 77% were resolved by PRNT Prolonged RNA persistence is still a rare event. Symptomatic pregnant women: 3/156 (1.9%) serum or urine samples were PCR Asymptomatic pregnant women: 1/762 (0.1%) serum or urine samples were PCR # asymptomatic pregnant women detected as confirmed or probable Zika: PCR IgM/PRNT Total Zika C Zika P Total

54 IgM Diagnostic Challenges Remain... Among symptomatic individuals, the false negative IgM rate is: 58% for samples collected <4 days 45.4% for samples collected < 7 days ~5.5% for samples collected >7 days False positive IgM rate: Symptomatic: 24.5% not confirmed Asymptomatic: 75.5% not confirmed Clinical sensitivity of IgM problematic < 7 days; lack of specificity requires PRNT PRNT confirmation Titers determined to be unreliable for accurate discrimination PRNT specificity is high with primary exposures; low with secondary exposures RTPCR Sensitivity: Serum = 51% Urine = 90.62% Specificity of urine or serum PCR = 100% Clinical sensitivity of PCR in serum is relatively low, but higher in urine & whole blood Still awaiting Dx assays that demonstrate significant improvements in sensitivity & specificity

55 What Can We Expect beyond 2017? South America d Zika (suspect and confirmed) cases Caribbean Latin America a Epidemiological Week Distribution of suspected and confirmed Zika cases by epidemiological week and subregion. Region of the Americas, [PAHO]

56 Acknowledgements Viral and Rickettsial Disease Lab Zoonotic and Vectorborne Disease Section Medical and Epidemiology Liaison Section Zika Team Vaccine Preventable Diseases and Herpes Virus Section Retrovirus Diagnostics Section CA Local Public Health Labs CDPH Infectious Disease Branch Vector Borne Disease Section CDPH Center for Family Health