An update on Zika virus infection

Background: The Zika virus (ZIKV) caused a large outbreak in the Americas leading to the declaration of a Public Health Emergency of International Concern in February 2016. A causal relation between infection and adverse congenital outcomes such as microcephaly was declared by the World Health Organization (WHO) informed by a systematic review structured according to a framework of ten dimensions of causality, based on the work of Bradford Hill. Subsequently, the evidence has continued to accumulate, which we incorporate in regular updates of the original work, rendering it a living systematic review. Methods: We present an update of our living systematic review on the causal relation between ZIKV infection and adverse congenital outcomes and between ZIKV and GBS for four dimensions of causality: strength of association, dose-response, specificity, and consistency. We assess the evidence published between January 18, 2017 and July 1, 2019. Results: We found that the strength of association between ZIKV infection and adverse outcomes from case-control studies differs according to whether exposure to ZIKV is assessed in the mother (OR 3.8, 95% CI: 1.7-8.7, I 2=19.8%) or the foetus/infant (OR 37.4, 95% CI: 11.0-127.1, I 2=0%). In cohort studies, the risk of congenital abnormalities was 3.5 times higher after ZIKV infection (95% CI: 0.9-13.5, I 2=0%). The strength of association between ZIKV infection and GBS was higher in studies that enrolled controls from hospital (OR: 55.8, 95% CI: 17.2-181.7, I 2=0%) than in studies that enrolled controls at random from the same community or household (OR: 2.0, 95% CI: 0.8-5.4, I 2=74.6%). In case-control studies, selection of controls from hospitals could have biased results. Conclusions: The conclusions that ZIKV infection causes adverse congenital outcomes and GBS are reinforced with the evidence published between January 18, 2017 and July 1, 2019.

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Zika Virus Infection as a Cause of Congenital Brain Abnormalities and Guillain-Barré Syndrome: Systematic Review.

Arthropod-borne viruses (arboviruses) have a long history of emerging to infect humans, but during recent decades, they have been spreading more widely and affecting larger populations. This is due to several factors, including increased air travel and uncontrolled mosquito vector populations. Emergence can involve simple spillover from enzootic (wildlife) cycles, as in the case of West Nile virus accompanying geographic expansion into the Americas; secondary amplification in domesticated animals, as seen with Japanese encephalitis, Venezuelan equine encephalitis, and Rift Valley fever viruses; and urbanization, in which humans become the amplification hosts and peridomestic mosquitoes, mainly Aedes aegypti, mediate human-to-human transmission. Dengue, yellow fever, chikungunya, and Zika viruses have undergone such urban emergence. We focus mainly on the latter two, which are recent arrivals in the Western Hemisphere. We also discuss a few other viruses with the potential to emerge through all of these mechanisms.

Zika, Chikungunya, and Other Emerging Vector-Borne Viral Diseases

Zika Virus and Its Associated Diseases Zika is a mosquito-borne flavivirus that can cause congenital defects, including microcephaly. Although most Zika virus infections are asymptomatic, rash, fev...

https://www.nejm.org/doi/pdf/10.1056/NEJMra1808246?listPDF=true

Zika Virus Infection — After the Pandemic

https://www.arca.fiocruz.br/bitstream/icict/18801/2/Robbiani%20DF%20Recurrent%20Potent%20Human%20Neutralizing%20Antibodies%20to%20Zika%20Virus....pdf

Recurrent Potent Human Neutralizing Antibodies to Zika Virus in Brazil and Mexico.

Importance Understanding the risk of birth defects associated with Zika virus infection during pregnancy may help guide communication, prevention, and planning efforts. In the absence of Zika virus, microcephaly occurs in approximately 7 per 10 000 live births. Objective To estimate the preliminary proportion of fetuses or infants with birth defects after maternal Zika virus infection by trimester of infection and maternal symptoms. Design, Setting, and Participants Completed pregnancies with maternal, fetal, or infant laboratory evidence of possible recent Zika virus infection and outcomes reported in the continental United States and Hawaii from January 15 to September 22, 2016, in the US Zika Pregnancy Registry, a collaboration between the CDC and state and local health departments. Exposures Laboratory evidence of possible recent Zika virus infection in a maternal, placental, fetal, or infant sample. Main Outcomes and Measures Birth defects potentially Zika associated: brain abnormalities with or without microcephaly, neural tube defects and other early brain malformations, eye abnormalities, and other central nervous system consequences. Results Among 442 completed pregnancies in women (median age, 28 years; range, 15-50 years) with laboratory evidence of possible recent Zika virus infection, birth defects potentially related to Zika virus were identified in 26 (6%; 95% CI, 4%-8%) fetuses or infants. There were 21 infants with birth defects among 395 live births and 5 fetuses with birth defects among 47 pregnancy losses. Birth defects were reported for 16 of 271 (6%; 95% CI, 4%-9%) pregnant asymptomatic women and 10 of 167 (6%; 95% CI, 3%-11%) symptomatic pregnant women. Of the 26 affected fetuses or infants, 4 had microcephaly and no reported neuroimaging, 14 had microcephaly and brain abnormalities, and 4 had brain abnormalities without microcephaly; reported brain abnormalities included intracranial calcifications, corpus callosum abnormalities, abnormal cortical formation, cerebral atrophy, ventriculomegaly, hydrocephaly, and cerebellar abnormalities. Infants with microcephaly (18/442) represent 4% of completed pregnancies. Birth defects were reported in 9 of 85 (11%; 95% CI, 6%-19%) completed pregnancies with maternal symptoms or exposure exclusively in the first trimester (or first trimester and periconceptional period), with no reports of birth defects among fetuses or infants with prenatal exposure to Zika virus infection only in the second or third trimesters. Conclusions and Relevance Among pregnant women in the United States with completed pregnancies and laboratory evidence of possible recent Zika infection, 6% of fetuses or infants had evidence of Zika-associated birth defects, primarily brain abnormalities and microcephaly, whereas among women with first-trimester Zika infection, 11% of fetuses or infants had evidence of Zika-associated birth defects. These findings support the importance of screening pregnant women for Zika virus exposure.

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Birth Defects Among Fetuses and Infants of US Women With Evidence of Possible Zika Virus Infection During Pregnancy.

Background: Placenta previa is associated with increased maternal and perinatal complications like malpresentation, premature labor, higher rates of caesarean section, peripartum hysterectomies, postpartum hemorrhage, sepsis, shock and retained placenta and even death. Antepartum haemorrhage may frequently result in low birth weight babies, preterm labour or repeated small events of haemorrhage causing chronic placental insufficiency and foetal growth retardation or intrauterine fetal death.Methods: This was a prospective study conducted in the department of obstetrics and gynaecology, SMGS, hospital, Jammu over a period of 1 year. All admitted cases of placenta previa were included in the study.Results: The total numbers of deliveries in one our hospital were 18567 during the study period. 364 patients admitted with antepartum heamorrhage so the incidence of APH in our hospital was 1.96%. 157 cases out of 346 were of placenta previa. It was observed that placenta previa cases were highest in the maternal age group of 26-30 yrs, i.e. 55.42%, 71.97% were multigravidae and those with prior caesarean section. 15.92 % had undergone peripartum hysterectomy due to massive PPH. The percentage of perinatal death was 18.23% and the main cause was prematurity.Conclusions: Based upon observation made during this study, it is concluded that placenta previa is a serious condition with significant maternal and perinatal morbidity and mortality. Improvements in management of placenta previa have helped in improving neonatal survival and reduce maternal morbidity and mortality.

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Jyoti Gupta

Papers

Birth Defects Among Fetuses and Infants of US Women With Evidence of Possible Zika Virus Infection During Pregnancy.

Maternal and perinatal outcomes in pregnancy associated with placenta previa