Causal or not: applying the Bradford Hill aspects of evidence to the association between Zika virus and microcephaly

Neonatal sepsis as a cause of retinopathy of prematurity: An etiological explanation

Retinopathy of prematurity (ROP) is a complex neonatal disorder with multiple contributing factors. In this paper we have mounted the evidence in support of the proposal that neonatal sepsis meets all requirements for being a cause of ROP (not a condition, mechanism, or even innocent bystander) by means of initiating the early stages of the pathomechanism of ROP occurrence, systemic inflammation. We use the model of etiological explanation, which distinguishes between two overlapping processes in ROP causation. It can be shown that sepsis can initiate the early stages of the pathomechanism via systemic inflammation (causation process) and that systemic inflammation can contribute to growth factor aberrations and the retinal characteristics of ROP (disease process). The combined contribution of these factors with immaturity at birth (as intrinsic risk modifier) and prenatal inflammation (as extrinsic facilitator) seems to provide a cogent functional framework of ROP occurrence. Finally, we apply the Bradford Hill heuristics to the available evidence. Taken together, the above suggests that neonatal sepsis is a causal inducer of ROP.

A new framework for host-pathogen interaction research

COVID-19 often manifests with different outcomes in different patients, highlighting the complexity of the host-pathogen interactions involved in manifestations of the disease at the molecular and cellular levels. In this paper, we propose a set of postulates and a framework for systematically understanding complex molecular host-pathogen interaction networks. Specifically, we first propose four host-pathogen interaction (HPI) postulates as the basis for understanding molecular and cellular host-pathogen interactions and their relations to disease outcomes. These four postulates cover the evolutionary dispositions involved in HPIs, the dynamic nature of HPI outcomes, roles that HPI components may occupy leading to such outcomes, and HPI checkpoints that are critical for specific disease outcomes. Based on these postulates, an HPI Postulate and Ontology (HPIPO) framework is proposed to apply interoperable ontologies to systematically model and represent various granular details and knowledge within the scope of the HPI postulates, in a way that will support AI-ready data standardization, sharing, integration, and analysis. As a demonstration, the HPI postulates and the HPIPO framework were applied to study COVID-19 with the Coronavirus Infectious Disease Ontology (CIDO), leading to a novel approach to rational design of drug/vaccine cocktails aimed at interrupting processes occurring at critical host-coronavirus interaction checkpoints. Furthermore, the host-coronavirus protein-protein interactions (PPIs) relevant to COVID-19 were predicted and evaluated based on prior knowledge of curated PPIs and domain-domain interactions, and how such studies can be further explored with the HPI postulates and the HPIPO framework is discussed.

Causation and causal inference in obstetrics-gynecology

Causation and causal inference are of utmost importance in obstetrics and gynecology. In many clinical situations, causal reasoning is involved in etiological explanations, diagnostic considerations, and conversations about prognosis. In this paper, we offer an overview of the philosophical accounts of causation that may not be familiar to, but still be appreciated by, the busy clinician. In our discussion, we do not try to simplify what is a rather complex range of ideas. We begin with an introduction to some important basic ideas, followed by 2 sections on the metaphysical and epistemological aspects of causality, which offer a more detailed discussion of some of its specific philosophical facets, using examples from obstetrical and gynecologic research and practice along the way. We hope our discussion will help deepen the thinking and discourse about causation and causal inference in gynecology and obstetrics.

Applying Concepts of Causal Inference to Infectious Bovine Keratoconjunctivitis

Establishing causation, otherwise known as causal assessment, is a difficult task, made more difficult by the variety of causal assessment frameworks available to consider. In this article, Bradford Hill viewpoints are used to discuss the evidence base for Moraxella bovis and Moraxella bovoculi being component causes of infectious bovine keratoconjunctivitis. Each of the nine Bradford Hill viewpoints are introduced and explained: strength, consistency, specificity, temporality, biologic gradient, plausibility, coherence, experiment, and analogy. Examples of how the viewpoints have been applied for other causal relations are provided, and then the evidence base for M bovis and M bovoculi is discussed.

Scoping review on the epidemiology, diagnostics and clinical significance of porcine astroviruses

Porcine astroviruses (PoAstVs) have been reported globally and are divided into at least five distinct lineages (PoAstV1-PoAsV5). The primary objective of this review was to summarize the scientific literature about the frequency of detection, associated clinical presentations and type of samples and diagnostic tools used for the detection of porcine astroviruses. The secondary objective was to summarize the body of knowledge about the causal role in disease of PoAstVs using the Bradford Hill framework. A search was conducted using Centre for Biosciences and Agriculture International (CABI), MEDLINE, American Association of Swine Veterinarians (AASV) Swine Information Library (SIL) abstracts, swine conferences including American College of Veterinary Pathologists (ACVP) and American Association of Veterinary Laboratory Diagnosticians (AAVLD). From 168 studies identified by the search, 29 studies were eligible. Results indicated that 69% (20/29) of the literature on PoAstVs have been published between 2011 and 2018. Of 29 papers, 52% were detection studies (15 of 29) and 48% (14 of 29) were case-control studies. Seventy-two per cent (21 of 29) reported differential diagnosis and 10% (3 of 29) reported histologic lesions, out of which 67% (2 of 3) associated the detection of PoAstV3 with development of polioencephalomyelitis. PCR-based assays were the most common diagnostic tools.

Maternal paracetamol intake and fetal ductus arteriosus constriction/closure: comprehensive signal evaluation using the Austin Bradford Hill criteria

PURPOSE

Acetaminophen (APAP) is available over-the-counter and widely regarded as safe for use in pregnancy. APAP has been used to close a persistently patent ductus arteriosus. Fetal constriction/closure of the ductus arteriosus (FCCDA), of public health interest given the drug's widespread use during pregnancy, is being monitored globally, including by the European Medicines Agency Pharmacovigilance Risk Assessment Committee. Our objective was to share a comprehensive signal evaluation of FCCDA with in utero APAP exposure to determine if the totality of evidence is sufficiently more consistent with one of the following two possibilities: (1) APAP never contributes to FCCDA (null hypothesis or H_O) versus (2) APAP may in some cases be at least a contributory cause of in utero DA narrowing (alternative hypothesis or H_A) to justify risk communication.

METHODS

To assess the relative support for H_O versus H_A, we synthesize and interpret within an Austin Bradford Hill criteria framework a comprehensive, cross-disciplinary set of published information and de novo analysis, including toxicology, epidemiology, clinical pharmacology, and clinical and quantitative pharmacovigilance analysis of spontaneous reports.

RESULTS

While residual uncertainty remains, the totality of information is more compatible with H_A than H₀, to the extent that it is reasonably possible that APAP may sometimes be at least a contributory cause of FCCDA.

CONCLUSION

It is reasonably possible that APAP may sometimes be at least a contributory cause of FCCDA, and this should therefore be communicated to stakeholders.

TRIAL REGISTRATION

CLINICALTRIALS.

GOV REGISTRATION

NOT APPLICABLE.

Onchocerca volvulus and epilepsy: A comprehensive review using the Bradford Hill criteria for causation

BACKGROUND

The possibility that onchocerciasis may cause epilepsy has been suggested for a long time, but thus far, an etiological link has not been universally accepted. The objective of this review is to critically appraise the relationship between Onchocerca volvulus and epilepsy and subsequently apply the Bradford Hill criteria to further evaluate the likelihood of a causal association.

METHODS

PubMed and gray literature published until September 15, 2020, were searched and findings from original research were synthesized. Adherence to the 9 Bradford Hill criteria in the context of onchocerciasis and epilepsy was determined to assess whether the criteria are met to strengthen the evidence base for a causal link between infection with O. volvulus and epilepsy, including the nodding syndrome.

RESULTS

Onchocerciasis as a risk factor for epilepsy meets the following Bradford Hill criteria for causality: strength of the association, consistency, temporality, and biological gradient. There is weaker evidence supporting causality based on the specificity, plausibility, coherence, and analogy criteria. There is little experimental evidence. Considering the Bradford Hill criteria, available data suggest that under certain conditions (high microfilarial load, timing of infection, and perhaps genetic predisposition), onchocerciasis is likely to cause epilepsy including nodding and Nakalanga syndromes.

CONCLUSION

Applying the Bradford Hill criteria suggests consistent epidemiological evidence that O. volvulus infection is a trigger of epilepsy. However, the pathophysiological mechanisms responsible for seizure induction still need to be elucidated.

Another piece of the Zika puzzle: assessing the associated factors to microcephaly in a systematic review and meta-analysis

BACKGROUND

Although it is known that Zika virus (ZIKV) infection during pregnancy may lead to microcephaly in the fetus, the prognostic factors associated with this tragic disorder remain unclear. We conducted a systematic review and meta-analysis to assess the prognostic factors associated with the incidence of microcephaly in congenital ZIKV infection.

METHODS

We conducted a comprehensive search in Ovid MEDLINE, Ovid MEDLINE (R) Epub ahead of print, Embase, Embase Classic, Web of Science, CINAHL, Cochrane CENTRAL, LILACS, and various thesis databases to identify human studies reporting microcephaly associated with congenital ZIKV infection. We requested primary data from the authors of the included studies to calculate summary estimates and conduct the meta-analysis of the most prevalent factors.

RESULTS

We screened 4106 titles and abstracts, and identified 12 studies for inclusion in the systematic review. The assessment of ZIKV infection and the definition of microcephaly varied among studies. A total of 6154 newborns/fetuses were enrolled; of those, 1120 (18.20%) had a diagnostic of ZIKV infection, of which 509 (45.45%) were diagnosed with microcephaly. Nine studies addressed the link between congenital ZIKV infection and neurological findings in newborns/fetuses. Half of the studies provided primary data. Three out of 11 factors of interest seem to be prognostic factors of microcephaly: infant's sex - males compared to females: Relative Risk (RR) 1.30, 95% Confidence Interval (95% CI) 1.14 to 1.49; the stage of pregnancy when infection occurred - infection in the first trimester of pregnancy compared to infection at other stages of pregnancy: RR 1.41, 95% CI 1.09 to 1.82; and asymptomatic infection compared to symptomatic infection during pregnancy: RR 0.68; 95% CI 0.60 to 0.77.

CONCLUSION

Our findings support the female-biased resistance hypothesis and reinforce the risk associated with the stage of pregnancy when ZIKV infection occurs. Continued surveillance of ZIKV infection during pregnancy is needed to identify additional factors that could contribute to developing microcephaly in affected fetuses.

PROTOCOL REGISTRATION

This systematic review was registered with the International Prospective Register of Systematic Reviews (PROSPERO), registration no. CRD 42018088075.

Epidemia de microcefalia e vírus Zika: a construção do conhecimento em epidemiologia

Em agosto de 2015, neuropediatras de hospitais públicos do Recife, Pernambuco, Brasil, observaram um aumento do número de casos de microcefalia desproporcional associado a anomalias cerebrais. Esse fato gerou comoção social, mobilização da comunidade acadêmica e levou o Ministério da Saúde a decretar emergência de saúde pública nacional, seguida pela declaração de emergência de saúde pública de interesse internacional da Organização Mundial da Saúde. A hipótese formulada para o fenômeno foi a infecção congênita pelo vírus Zika (ZIKV), com base na correlação espaço-temporal e nas características clínico-epidemiológicas das duas epidemias. Evidências se acumularam e no âmbito do raciocínio epidemiológico preencheram critérios que deram sustentação à hipótese. Sua plausibilidade está ancorada no neurotropismo do ZIKV demonstrado em animais, atingindo neurônios progenitores do cérebro em desenvolvimento, e em seres humanos devido às complicações neurológicas observadas em adultos após a infecção. O isolamento do RNA e antígenos virais no líquido amniótico de mães infectadas e em cérebros de neonatos e fetos com microcefalia contribuíram para demonstrar a consistência da hipótese. O critério de temporalidade foi contemplado ao se identificar desfechos desfavoráveis em uma coorte de gestantes com exantema e positivas para o ZIKV. Finalmente, o primeiro estudo caso-controle conduzido demonstrou existir uma forte associação entre microcefalia e infecção congênita pelo ZIKV. O conhecimento construído no âmbito do paradigma epidemiológico recebeu a chancela da comunidade científica, construindo o consenso de uma relação causal entre o ZIKV e a epidemia de microcefalia.

Hill's Heuristics and Explanatory Coherentism in Epidemiology

In this essay, I argue that Ted Poston's theory of explanatory coherentism is well-suited as a tool for causal explanation in the health sciences, particularly in epidemiology. Coherence has not only played a role in epidemiology for more than half a century as one of Hill's viewpoints, it can also provide background theory for the development of explanatory systems by integrating epidemiologic evidence with a diversity of other error-independent data. I propose that computational formalization of Hill's viewpoints in an explanatory coherentist framework would provide an excellent starting point for a formal epistemological (knowledge-theoretical) project designed to improve causal explanation in the health sciences. As an example, I briefly introduce Paul Thagard's ECHO system and offer my responses to possible objections to my proposal.

Zika Virus: Recent Advances towards the Development of Vaccines and Therapeutics

Zika is a rapidly emerging public health threat. Although clinical infection is frequently mild, significant neurological manifestations have been demonstrated in infants born to Zika virus (ZIKV) infected mothers. Due to the substantial ramifications of intrauterine infection, effective counter-measures are urgently needed. In order to develop effective anti-ZIKV vaccines and therapeutics, improved animal models and a better understanding of immunological correlates of protection against ZIKV are required. This review will summarize what is currently known about ZIKV, the clinical manifestations and epidemiology of Zika as well as, the development of animal models to study ZIKV infection, host immune responses against ZIKV, and the current state of development of vaccines and therapeutics against ZIKV.

Emerging Infectious Diseases and Blood Safety: Modeling the Transfusion-Transmission Risk

While the transfusion-transmission (TT) risk associated with the major transfusion-relevant viruses such as HIV is now very low, during the last 20 years there has been a growing awareness of the threat to blood safety from emerging infectious diseases, a number of which are known to be, or are potentially, transfusion transmissible. Two published models for estimating the transfusion-transmission risk from EIDs, referred to as the Biggerstaff-Petersen model and the European Upfront Risk Assessment Tool (EUFRAT), respectively, have been applied to several EIDs in outbreak situations. We describe and compare the methodological principles of both models, highlighting their similarities and differences. We also discuss the appropriateness of comparing results from the two models. Quantitating the TT risk of EIDs can inform decisions about risk mitigation strategies and their cost-effectiveness. Finally, we present a qualitative risk assessment for Zika virus (ZIKV), an EID agent that has caused several outbreaks since 2007. In the latest and largest ever outbreak, several probable cases of transfusion-transmission ZIKV have been reported, indicating that it is transfusion-transmissible and therefore a risk to blood safety. We discuss why quantitative modeling the TT risk of ZIKV is currently problematic.

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During the last 20 years there has been a growing awareness of the threat to blood safety from emerging infectious diseases (EIDs), a number of which are known to be, or are potentially, transfusion-transmissible.

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The transfusion-transmission risk of EID agents can be estimated by risk modeling which can form an important part of risk assessments and inform decisions regarding risk mitigation strategies.

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We describe and compare the methodological principles of two published risk models for estimating the transfusion transmission risk of EIDs.

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We use Zika virus as a case study to demonstrate that reliable risk modeling for EID agents can be problematic due to the uncertainty of the input parameters.

Does Zika Virus Cause Microcephaly - Applying the Bradford Hill Viewpoints

INTRODUCTION

Zika virus has been documented since 1952, but been associated with mild, self-limiting disease. Zika virus is classified as an arbovirus from a family of Flaviviridae and primarily spread by Aedes Aegypti mosquitos. However, in a large outbreak in Brazil in 2015, Zika virus has been associated with microcephaly.

METHODS

In this review we applied the Bradford-Hill viewpoints  to investigate the association between Zika virus and microcephaly. We examined historical studies, available data and also compared historical rates of microcephaly prior to the Zika virus outbreak. The available evidence was reviewed against the Bradford Hill viewpoints.

RESULTS

All  the nine criteria were met to varying degrees: strength of association, consistency of the association, specificity, temporality, plausibility, coherence, experimental evidence, biological gradient and analogy. Conclusion: Using the Bradford Hill Viewpoints as an evaluation framework for causation is highly suggestive that the association between Zika virus and microcephaly is causal. Further studies using animal models on the viewpoints which were not as strongly fulfilled would be helpful.

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

BACKGROUND

The World Health Organization (WHO) stated in March 2016 that there was scientific consensus that the mosquito-borne Zika virus was a cause of the neurological disorder Guillain-Barré syndrome (GBS) and of microcephaly and other congenital brain abnormalities based on rapid evidence assessments. Decisions about causality require systematic assessment to guide public health actions. The objectives of this study were to update and reassess the evidence for causality through a rapid and systematic review about links between Zika virus infection and (a) congenital brain abnormalities, including microcephaly, in the foetuses and offspring of pregnant women and (b) GBS in any population, and to describe the process and outcomes of an expert assessment of the evidence about causality.

METHODS AND FINDINGS

The study had three linked components. First, in February 2016, we developed a causality framework that defined questions about the relationship between Zika virus infection and each of the two clinical outcomes in ten dimensions: temporality, biological plausibility, strength of association, alternative explanations, cessation, dose-response relationship, animal experiments, analogy, specificity, and consistency. Second, we did a systematic review (protocol number CRD42016036693). We searched multiple online sources up to May 30, 2016 to find studies that directly addressed either outcome and any causality dimension, used methods to expedite study selection, data extraction, and quality assessment, and summarised evidence descriptively. Third, WHO convened a multidisciplinary panel of experts who assessed the review findings and reached consensus statements to update the WHO position on causality. We found 1,091 unique items up to May 30, 2016. For congenital brain abnormalities, including microcephaly, we included 72 items; for eight of ten causality dimensions (all except dose-response relationship and specificity), we found that more than half the relevant studies supported a causal association with Zika virus infection. For GBS, we included 36 items, of which more than half the relevant studies supported a causal association in seven of ten dimensions (all except dose-response relationship, specificity, and animal experimental evidence). Articles identified nonsystematically from May 30 to July 29, 2016 strengthened the review findings. The expert panel concluded that (a) the most likely explanation of available evidence from outbreaks of Zika virus infection and clusters of microcephaly is that Zika virus infection during pregnancy is a cause of congenital brain abnormalities including microcephaly, and (b) the most likely explanation of available evidence from outbreaks of Zika virus infection and GBS is that Zika virus infection is a trigger of GBS. The expert panel recognised that Zika virus alone may not be sufficient to cause either congenital brain abnormalities or GBS but agreed that the evidence was sufficient to recommend increased public health measures. Weaknesses are the limited assessment of the role of dengue virus and other possible cofactors, the small number of comparative epidemiological studies, and the difficulty in keeping the review up to date with the pace of publication of new research.

CONCLUSIONS

Rapid and systematic reviews with frequent updating and open dissemination are now needed both for appraisal of the evidence about Zika virus infection and for the next public health threats that will emerge. This systematic review found sufficient evidence to say that Zika virus is a cause of congenital abnormalities and is a trigger of GBS.

Neurological manifestations of Zika virus infection

Zika virus (ZIKV) is a flavivirus (Flaviviridae family) transmitted mainly by Aedes mosquitoes. The virus was restricted to the African continent until its spread to south-east Asia in the 1980's, the Micronesia in 2007, the French Polynesia in 2013 and, more recently in the Americas in 2015, where, up to date, the World Health Organization (WHO) has estimated about 3-4 million total cases of ZIKV infection. During outbreaks in the French Polynesia and Brazil in 2013 and 2015, respectively, national health authorities reported potential neurological complications of ZIKV disease, chiefly an upsurge in Guillain-Barré syndrome, which coincided with ZIKV outbreaks. On the other hand, the emergence of ZIKV in Brazil has been associated with a striking increase in the number of reported cases of microcephaly in fetus and newborns, twenty times higher than in that reported in previous years. While investigations are currently assessing whether there is an actual association between neurological complications and ZIKV infections, the evidence was enough worrisome for WHO to declare a public health emergency of international concern. Here we present an updated review addressing what is currently known about the possible association between ZIKV infection and the development of severe neurological disorders.

Epidemiologic investigation of a family cluster of imported ZIKV cases in Guangdong, China: probable human-to-human transmission

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus that can potentially threaten South China. A Chinese family of four returning from Venezuela to China was found to be positive for ZIKV when the youngest son's fever was first detected at an airport immigration inspection. They were isolated temporarily in a local hospital in Enping city, Guangdong province, where their clinical data were recorded and urine and saliva were collected to isolate ZIKV and to obtain viral sequences. All of them except the mother presented mild symptoms of rash and fever. Envelope gene sequences from the father, daughter and son were completely identical. Phylogenetic analysis demonstrated that this strain is similar to several imported strains reported in recent months, which are all clustered into a group isolated from 2015 ZIKA outbreaks in Brazil. Together with the climatic features in Venezuela, New York and Guangdong in February, it can be concluded that our subjects are imported cases from Venezuela. With the same viral sequence being shared between family members, neither direct human-to-human nor vector transmission can be ruled out in this study, but the former seems more likely. Although our subjects had mild illness, epidemiologists and public health officials should be aware of the risk of further expansion of ZIKV transmission by local competent vectors.

The global threat of Zika virus to pregnancy: epidemiology, clinical perspectives, mechanisms, and impact

Zika virus (ZIKV) is a mosquito-borne flavivirus that has newly emerged as a significant global threat, especially to pregnancy. Recent major outbreaks in the Pacific and in Central and South America have been associated with an increased incidence of microcephaly and other abnormalities of the central nervous system in neonates. The causal link between ZIKV infection during pregnancy and microcephaly is now strongly supported. Over 2 billion people live in regions conducive to ZIKV transmission, with ~4 million infections in the Americas predicted for 2016. Given the scale of the current pandemic and the serious and long-term consequences of infection during pregnancy, the impact of ZIKV on health services and affected communities could be enormous. This further highlights the need for a rapid global public health and research response to ZIKV to limit and prevent its impact through the development of therapeutics, vaccines, and improved diagnostics. Here we review the epidemiology of ZIKV; the threat to pregnancy; the clinical consequences and broader impact of ZIKV infections; and the virus biology underpinning new interventions, diagnostics, and insights into the mechanisms of disease.