A nonstandard finite difference scheme for a time-fractional model of Zika virus transmission

In this work, we investigate the transmission dynamics of the Zika virus, considering both a compartmental model involving humans and mosquitoes and an extended model that introduces a non-human primate (monkey) as a second reservoir host. The novelty of our approach lies in the later generalization of the model using a fractional time derivative. The significance of this study is underscored by its contribution to understanding the complex dynamics of Zika virus transmission. Unlike previous studies, we incorporate a non-human primate reservoir host into the model, providing a more comprehensive representation of the disease spread. Our results reveal the importance of utilizing a nonstandard finite difference (NSFD) scheme to simulate the disease's dynamics accurately. This NSFD scheme ensures the positivity of the solution and captures the correct asymptotic behavior, addressing a crucial limitation of standard solvers like the Runge-Kutta Fehlberg method (ode45). The numerical simulations vividly demonstrate the advantages of our approach, particularly in terms of positivity preservation, offering a more reliable depiction of Zika virus transmission dynamics. From these findings, we draw the conclusion that considering a non-human primate reservoir host and employing an NSFD scheme significantly enhances the accuracy and reliability of modeling Zika virus transmission. Researchers and policymakers can use these insights to develop more effective strategies for disease control and prevention.

Analysis of the spatial distribution of cases of Zika virus infection and congenital Zika virus syndrome in a state in the southeastern region of Brazil: Sociodemographic factors and implications for public health

OBJECTIVE

To perform spatial distribution analysis of reported cases of Zika virus and congenital Zika syndrome (CZS) in the state of Espírito Santo, Brazil, by neighborhood, and relate the results to sociodemographic indicators and implications for the health process.

METHODS

An ecological study using data from the 2016 National Notifiable Diseases Surveillance System, epidemiological records, and information on neighborhoods of families confirmed with CZS from qualitative field research.

RESULTS

Sociodemographic indicators were analyzed in three distinct groups: general population with Zika virus, pregnant women with Zika virus, and cases of CZS visited. For the three groups, average literacy rates were 71.1%, 71.0%, and 68.3%; the average income per minimum wage was 1.4, 1.1, and 1.4; sanitary sewage coverage was 75.6%, 76.1%, and 71.4%; garbage coverage was 90.8%, 91.2%, and 89.2%; and water supply was 93.8%, 94.1% and 93.8%, respectively. Socioeconomic indicators showed no significant differences between groups, although they were above the national average. A nonsignificant variation of 68.3%-71.1% was seen in the average literacy level above 15 years of age.

CONCLUSION

Socioeconomic and demographic indicators of cases of Zika virus infection and CZS may indicate that the outbreak had different impacts according to class, social group, or gender, reflecting the persistence and social geography of inequality in Brazil.

Going Viral 2019: Zika, Chikungunya, and Dengue

Chikungunya and Zika virus infections are emerging diseases in the Americas, and dengue continues to be the most prevalent arthropod-borne virus in the world. These arbovirus diseases may spread by endemic transmission or as travel-related infections and have rapidly expanded their geographic distribution secondary to vector spread. All 3 share a similar clinical picture that includes a maculopapular rash. Zika is characterized by pruritic rash, low-grade fever, and arthralgia. Congenital nervous system malformations are a growing public-health concern. Chikungunya distinctive dermatologic manifestations include facial melanosis and bullous eruption. Dengue bleeding complications may be life-threatening and require inpatient management.

[Congenital Zika syndrome: sociodemographic profile of mothersSíndrome congénito por el virus del Zika: perfil sociodemográfico de las madres]

Objetivo

Descrever o perfil sociodemográfico de mães de crianças com síndrome congênita do Zika.

Métodos

Trata-se de um estudo descritivo, transversal, de abordagem quantitativa. Foram convidadas a participar todas as 39 mães de bebês nascidos vivos entre os casos notificados em 2015 e 2016 com diagnóstico confirmado de síndrome congênita do Zika no Estado da Saúde do Espírito Santo. Dessas 39 mulheres, 25 concordaram em participar. Para a coleta de dados foram utilizados um formulário para identificar o perfil sociodemográfico e um diário de campo.

Resultados

Das 25 mães, 19 (74,0%) se declararam não brancas e 16 declararam (64,0%) possuir companheiro. Quanto à escolaridade, 12 (48,0%) possuíam ensino médio completo. A renda domiciliar per capita variou de nenhuma renda até US$ 1 111,11; 12 mulheres (48,0%) tinham entre nenhuma renda e renda de US$ 61,72. Quanto à moradia, 17 (68,0%) residiam em áreas de periferia com condições precárias. Das 25 mulheres, 16 (64,0%) apresentavam vínculo empregatício antes da gestação; e dessas 16 com vínculo, 12 (75,0%) foram demitidas ou pediram demissão após o nascimento do bebê.

Conclusões

O perfil das mães revelou que a epidemia não foi equânime e atingiu preferencialmente mulheres de baixa renda e de estratos sociais desfavorecidos. Nesse sentido, acredita-se que a doença possa ser determinada pelas desigualdades sociais de saúde presentes no país. Os dados descritos podem fornecer subsídios para o planejamento de ações efetivas para garantir uma rede de proteção social para crianças com síndrome congênita do Zika e suas famílias.

Systematic review of factors associated with the development of Guillain-Barré syndrome 2007-2017: what has changed?

OBJECTIVE

The objective of this study was to describe the factors associated with the development of Guillain-Barré syndrome, both infectious and non-infectious, during and after the A(H1N1) influenza pandemic in 2009 and the recent Zika virus epidemic in the Americas.

METHOD

Systematic review of literature on factors associated with the development of the Guillain-Barré syndrome published between 2007 and 2017 listed in EBSCO, MEDLINE and LILACS databases. The quality of the studies was evaluated using the Newcastle Ottawa Scale.

RESULTS

Thirty-four articles met inclusion criteria and were selected for analysis. Their quality was considered good in relation to most of the items evaluated. Many aetiological agents had the results of association with Guillain-Barré syndrome, among them Campylobacter jejuni, influenza vaccine - both pandemic and seasonal vaccines, respiratory infection, gastrointestinal infection among others. The aetiological agents found are, in most part, the same reported prior to the study period. The association with surgeries, chikungunya virus (CHIKV), Zika virus and quadrivalent human papillomavirus vaccine stand out as new aetiological agents in the list of the various possible agents that trigger Guillain-Barré syndrome reported in the study period. There were no Brazilian studies identified during this period.

CONCLUSIONS

The results of the review reaffirmed C. jejuni as the major trigger of GBS, whereas the association of influenza vaccines and GBS is less clear; Zika virus infection in association with GBS was found in only one study.

Zika and the Eye: Pieces of a Puzzle

Zika virus (ZIKV) is an arbovirus mainly transmitted to humans by mosquitoes from Aedes genus. Other ways of transmission include the perinatal and sexual routes, blood transfusion, and laboratory exposure. Although the first human cases were registered in 1952 in African countries, outbreaks were only reported since 2007, when entire Pacific islands were affected. In March 2015, the first cases of ZIKV acute infection were notified in Brazil and, to date, 48 countries and territories in the Americas have confirmed local mosquito-borne transmission of ZIKV. Until 2015, ZIKV infection was thought to only cause asymptomatic or mild exanthematous febrile infections. However, after explosive ZIKV outbreaks in Polynesia and Latin American countries, it was confirmed that ZIKV could also lead to Guillain-Barré syndrome and congenital birth abnormalities. These abnormalities, which can include neurologic, ophthalmologic, audiologic, and skeletal findings, are now considered congenital Zika syndrome (CZS). Brain abnormalities in CZS include cerebral calcifications, malformations of cortical development, ventriculomegaly, lissencephaly, hypoplasia of the cerebellum and brainstem. The ocular findings, which are present in up to 70% of infants with CZS, include iris coloboma, lens subluxation, cataract, congenital glaucoma, and especially posterior segment findings. Loss of retinal pigment epithelium, the presence of a thin choroid, a perivascular choroidal inflammatory infiltrate, and atrophic changes within the optic nerve were seen in histologic analyses of eyes from deceased fetuses. To date, there is no ZIKV licensed vaccines or antiviral therapies are available for treatment. Preventive measures include individual protection from mosquito bites, control of mosquito populations and the use of barriers measures such as condoms during sexual intercourse or sexual abstinence for couples either at risk or after confirmed infection. A literature review based on studies that analyzed ocular findings in mothers and infants with CZS, with or without microcephaly, was conducted and a theoretical pathophysiologic explanation for ZIKV-ocular abnormalities was formulated.

Acute Zika Virus Infection in an Endemic Area Shows Modest Proinflammatory Systemic Immunoactivation and Cytokine-Symptom Associations

An early immune response to Zika virus (ZIKV) infection may determine its clinical manifestation and outcome, including neurological effects. However, low-grade and transient viremia limits the prompt diagnosis of acute ZIKV infection. We have investigated the plasma cytokine, chemokine, and growth factor profiles of 36 individuals from an endemic area displaying different symptoms such as exanthema, headache, myalgia, arthralgia, fever, hyperemia, swelling, itching, and nausea during early-phase infection. These profiles were then associated with symptoms, revealing important aspects of the immunopathophysiology of ZIKV infection. The levels of some cytokines/chemokines were significantly higher in acute ZIKV-infected individuals compared to healthy donors, including interferon (IFN) gamma-induced protein 10 (IP-10), regulated on activation, normal T cell expressed and secreted (RANTES), IFN-γ, interleukin (IL)-9, IL-7, IL-5, and IL-1ra, including some with predominantly immunoregulatory activity. Of note, we found that higher levels of IP-10 and IL-5 in ZIKV-infected individuals were strongly associated with exanthema and headache, respectively. Also, higher levels of IL-1ra were associated with subjects with arthralgia, whereas those with fever showed lower levels of granulocyte-colony stimulating factor (G-CSF). No correlation was observed between the number of symptoms and ZIKV viral load. Interestingly, only IP-10 showed significantly decreased levels in the recovery phase. In conclusion, our results indicate that acute ZIKV infection in a larger cohort resident to an endemic area displays a modest systemic immune activation profile, involving both proinflammatory and immunoregulatory cytokines and chemokines that could participate of virus control. In addition, we showed that differential cytokine/chemokine levels are related to specific clinical symptoms, suggesting their participation in underlying mechanisms.

Current priorities in the Zika response

Zika virus (ZIKV), a single-stranded RNA virus of the Flaviviridae family, is an arbovirus (viruses transmitted by arthropods) transmitted to humans and non-human primates through the bites of infected female Aedes sp. mosquitoes. Although first isolated in 1947, it only recently emerged as a global threat, present in several countries resulting in a pandemic scenario. ZIKV infections may have severe outcomes, such as neurological impairment, and with the intrinsic ability of inducing microcephaly in fetuses of infected pregnant women, the virus has become a major public health problem. This review discusses some advances in diagnosis; vaccine development and the problems associated with their administration; the importance of the cross-reactivity with other flaviviruses in protecting or worsening the disease; the implications of the recent outbreak caused by the virus in the world; and future prospects for the complete understanding of this disease.

[Zika virus infection and the nervous system]

Zika virus is an arbovirus from the family of flaviviruses, which is transmitted by the mosquito Aedes aegyptii and also by the Asian mosquito Aedes albopticus. The largest observed Zika virus epidemic is currently taking place in North and South America, in the Caribbean, southern USA and Southeast Asia. In most cases the infection is an unspecific, acute, febrile disease. Neurological manifestations consist mainly of microcephaly in newborns and Guillain-Barré syndrome but other rare manifestations have also become known in the meantime, such as meningoencephalitis and myelitis. Therefore, the Zika virus, similar to other flaviviruses, has neuropathogenic properties. In particular, the drastic increase in microcephaly cases in Brazil has induced great research activities. The virus is transmitted perinatally and can be detected in the amniotic fluid, placenta and brain tissue of the newborn. Vaccination or a causal therapy does not yet exist. The significant increase in Guillain-Barré syndrome induced by the Zika virus was observed during earlier outbreaks. In the meantime, scientifically clear connections between a Zika virus infection and these neurological manifestations have been shown. Long-term studies and animal models should be used for a better understanding of the pathomechanisms of this disease.

Zika virus and the eye

PURPOSE OF REVIEW

The aim of this study was to review the ocular findings related to the Zika virus (ZIKV) based on the main studies published to date, describe the patterns of the lesions and risk factors, and identify the public health implications and scientific importance of this emerging disease.

RECENT FINDINGS

In most studies, the ZIKV seems related to congenital ocular lesions and most mothers reported mild symptoms during the first pregnancy trimester. Five fundus patterns were seen most often: macular chorioretinal atrophy, chorioretinal atrophy elsewhere, focal pigmentary changes in the macular region, optic nerve abnormalities and combined types. A few studies have suggested that the ZIKV might damage the anterior segment of these babies' eyes. Few reports have described the ocular complications seen in adults during the acute infection, including conjunctivitis, iridocyclitis and chorioretinitis.

SUMMARY

Infants with congenital Zika syndrome might have vision-threatening fundus abnormalities. Although the full spectrum of ocular lesions caused by the ZIKV infection is not yet determined, a distinctive new disease has been observed. Recognition of these lesions by ophthalmologists can help ensure appropriate etiologic evaluation and clinical investigation to define the range of anomalies in an affected infant and determine essential follow-up and ongoing care.

The Emerging Zika Virus Threat: A Guide for Dermatologists

We provide a guide for dermatologists to follow if they encounter patients with a rash and clinical history suspicious of Zika virus infection, including diagnostic testing and management options. We also provide an illustrative case report of a patient from Brazil who was diagnosed with Zika virus infection after presenting with a generalized pruritic rash. One of the most prominent symptoms of Zika virus infection is a cutaneous eruption. As such, it is especially necessary for dermatologists to understand this virus so that they may appropriately recognize this entity as a diagnostic consideration in the clinic. The rash associated with Zika virus infection is most commonly an erythematous maculopapular eruption that presents after an initial 3-4 days of fever, headache, and arthralgia or myalgia. The rash typically lasts for an average of 6 days, and can spread to involve any part of the body, including the face, torso, extremities, palms, and soles.

Arboviruses and the eye

Arthropod-borne viruses, or arboviruses, are viruses that are transmitted through the bites of mosquitoes and ticks. There are numerous arboviruses throughout the world capable of causing human disease spanning different viral families and genera. Recently, dengue, chikungunya, and zika viruses have emerged as increasingly important arboviruses that can cause human disease, however no specific treatment or vaccine is available for them. In addition, ocular manifestations of these diseases have become more prevalent over the past few years. This review highlights the current understanding on the pathogenesis, systemic changes and ocular findings, emphasizing the retinal manifestations related to dengue, chikungunya, and zika viruses.

Zika virus infection or the future of infectious diseases

Zika virus belongs to the Flaviridae, an extended phylogenetic family containing dengue or yellow fever, viruses whose shared main vector are Aedes aegypti mosquitoes. The virus originally came from Central African simian reservoirs and, from there, expanded rapidly across the Pacific to South America. The disease is an example of exantematic fever usually mild. Mortality is very low and mainly limited to secondary Guillain-Barré or foetal microcephaly cases. Diagnostic confirmation requires a RT-PCR in blood up to the 5th day from the onset or in urine up to the 10-14th day. Specific IgM are identifiable from the 5th symptomatic day. Clinically, a suspected case should comply with: (a) a journey to epidemic areas; (b) a clinically compatible appearance with fever and skin rash, and (c) a generally normal blood count/basic biochemistry. There is some evidence that causally relates Zika virus infection with foetal microcephaly. While waiting for definitive data, all pregnant women coming from Central or South America should be tested for Zika virus.

Zika virus infection and pregnancy: what we do and do not know

Recent data strongly suggest an association between the current outbreak of ZIKA virus (ZIKV) in many countries of Central and South America and a sharp increase in the detection of microcephaly and fetal malformations. The link with brain defect, which has been detected mainly in some areas of Brazil, is supported by the following evidence: (1) ZIKV transmission from infected pregnant women to their fetuses; (2) the potential of ZIKV to determine a specific congenital fetal syndrome characterized by abnormalities involving primarily the developing brain and eye. In particular, the risk of transmission and congenital disease appears to be restricted to mother's infection during the first trimester of pregnancy. Among brain defects, microcephaly, brain calcifications, and ventriculomegaly are the most frequent abnormalities of the central nervous system detected so far. However, relevant information on effect of maternal infection with ZIKV on the fetus is still limited. In this review, we focus our attention on current knowledge about ZIKV infection in pregnancy, discussing relevant issues and open problems which merit further investigation.

Guillain-Barré syndrome: causes, immunopathogenic mechanisms and treatment

INTRODUCTION

Guillain-Barré syndrome is a rare disease representing the most frequent cause of acute flaccid symmetrical weakness of the limbs and areflexia usually reaching its peak within a month. The etiology and pathogenesis remain largely enigmatic and the syndrome results in death or severe disability in 9-17% of cases despite immunotherapy. Areas covered: In terms of etiology, Guillain-Barré syndrome is linked to Campylobacter infection but less than 0.1% of infections result in the syndrome. In terms of pathogenesis, activated macrophages and T cells and serum antibodies against gangliosides are observed but their significance is unclear. Expert commentary: Guillain-Barré syndrome is a heterogeneous condition with numerous subtypes and recent data point towards the role of ganglioside epitopes by immunohistochemical methods. Ultimately, the syndrome results from a permissive genetic background on which environmental factors, including infections, vaccination and the influence of aging, lead to disease.

[Emerging viral infections and hepatotropic virus]

Environmental degradation, population movements and urban agglomerations have broken down the borders for infectious diseases. The expansion of microorganisms has entered an increasing area of transmission vectors. The lack of immunity of the population leads to an increased risk of spreading infectious diseases. Furthermore, the decline in vaccination rates in developed countries and socio-economic difficulties in large regions has meant that diseases in the process of eradication have re-emerged. That is why health care workers must be trained to avoid delaying in diagnosis and to accelerate the implementation of public health measures. A great deal of education and health prevention should fall under the responsibilities of travellers who move around different regions.

[Zika virus infection or the future of infectious diseases]

El virus Zika es un Flavivirus filogenéticamente cercano al de la fiebre amarilla o del dengue, cuyo vector principal es el mosquito Aedes aegypti. El virus procede de un reservorio simiano africano y ha protagonizado una expansión fulminante a través del Pacífico hasta Sudamérica. Provoca una enfermedad leve caracterizada por fiebre con exantema. La mortalidad se circunscribe a casos de Guillain-Barré y de malformación encefálica fetal con microcefalia.

Un caso sospechoso será aquel con: a) antecedente epidemiológico de desplazamiento a zona endémica; b) cuadro pseudogripal con exantema, y c) hemograma/bioquímica levemente alteradas o normales.

La confirmación diagnóstica requiere identificar al virus por RT-PCR en sangre (hasta el quinto día sintomático), orina (hasta el día 10-14) o IgM específicas a partir del quinto día. Existe alguna evidencia que da soporte a la relación causa-efecto con la microcefalia fetal. A la espera de datos definitivos, las mujeres embarazadas procedentes de Centro y Sudamérica deben ser testadas para descartar la infección.