The global trends and regional differences in incidence of Zika virus infection and implications for Zika virus infection prevention

The global incidence and trends of three common flavivirus infections (Dengue, yellow fever, and Zika) from 2011 to 2021

Background

Flavivirus pose a continued threat to global health, yet their worldwide burden and trends remain poorly quantified. We aimed to evaluate the global, regional, and national incidence of three common flavivirus infections (Dengue, yellow fever, and Zika) from 2011 to 2021.

Methods

Data on the number and rate of incidence for the three common flavivirus infection in 204 countries and territories were retrieved from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021. The estimated annual percent change (EAPC) was calculated to quantify the temporal trend during 2011-2016, 2016-2019, and 2019-2021, respectively.

Results

In 2021, an estimated 59,220,428 individuals were infected globally, comprising 58,964,185 cases of dengue, 86,509 cases of yellow fever, and 169,734 cases of Zika virus infection. The age-standardized incidence rate (ASIR) of the three common flavivirus infections increased by an annual average of 5.08% (95% CI 4.12 to 6.05) globally from 2011 to 2016, whereas decreased by an annual average of -8.37% (95% CI -12.46 to -4.08) per year between 2016 to 2019. The ASIR remained stable during 2019-2021, with an average change of 0.69% (95% CI -0.96 to 2.37) per year globally for the three common flavivirus infections. Regionally, the burden of the three common flavivirus infections was primarily concentrated in those regions with middle income, such as South Asia, Southeast Asia, and Tropical Latin America. Additionally, at the country level, there was an inverted "U" relationship between the SDI level and the ASI. Notably, an increase in the average age of infected cases has been observed worldwide, particularly in higher-income regions.

Conclusion

Flavivirus infections are an expanding public health concern worldwide, with considerable regional and demographic variation in the incidence. Policymakers and healthcare providers must stay vigilant regarding the impact of COVID-19 and other environmental factors on the risk of flavivirus infection and be prepared for potential future outbreaks.

Multi-omics analysis of antiviral interactions of Elizabethkingia anophelis and Zika virus

The microbial communities residing in the mosquito midgut play a key role in determining the outcome of mosquito pathogen infection. Elizabethkingia anophelis, originally isolated from the midgut of Anopheles gambiae possess a broad-spectrum antiviral phenotype, yet a gap in knowledge regarding the mechanistic basis of its interaction with viruses exists. The current study aims to identify pathways and genetic factors linked to E. anophelis antiviral activity. The understanding of E. anophelis antiviral mechanism could lead to novel transmission barrier tools to prevent arboviral outbreaks. We utilized a non-targeted multi-omics approach, analyzing extracellular lipids, proteins, metabolites of culture supernatants coinfected with ZIKV and E. anophelis. We observed a significant decrease in arginine and phenylalanine levels, metabolites that are essential for viral replication and progression of viral infection. This study provides insights into the molecular basis of E. anophelis antiviral phenotype. The findings lay a foundation for in-depth mechanistic studies.

Antiviral activity of theaflavins against Zika virus in vivo and in vitro

INTRODUCTION

The prevalence and infection of the Zika virus (ZIKV) have recently posed a major threat to global public health security. However, there is currently a lack of specific vaccines and effective antiviral drugs for ZIKV infection.

METHODS

Theaflavins TF1 and TF2 were selected by evaluating the anti-Zika virus activity of four kinds of theaflavins in vitro. Subsequently, in vivo, we investigated the effects of TF1 and TF2 on weight, survival, tissue viral load, and cytokines in ZIKV-infected mice.

RESULTS

We compared the anti-ZIKV activity of four theaflavins (TFs) in cells and found that TF1 and TF2b significantly inhibited the replication of ZIKV/Z16006 toxic strain in BHK and Vero cells by inhibiting the replication and release of ZIKV, while no similar effects were observed for TF2a and TF3. In vivo assay, we only found that TF2b improved the survival rate of infected mice. In tissues of ZIKV-infected mice, the viral load was higher in spleen and blood, followed by liver, epididymis, and testis, the lowest in muscle. Additionally, TF2b treatment significantly reduced the expression of cytokines (IL-6, IL-1β, TNF-α) and chemokines (CCL2, CCL5, CXCL10) induced by ZIKV infection.

CONCLUSIONS

These findings suggest that TF2b has a potent antiviral effect and can be used as a potential candidate for the treatment of ZIKV infection.

Identification and characterization of a nonbiological small-molecular mimic of a Zika virus conformational neutralizing epitope

Antigenic similarities between Zika virus (ZIKV) and other flaviviruses pose challenges to the development of virus-specific diagnostic tools and effective vaccines. Starting with a DNA-encoded one-bead-one-compound combinatorial library of 508,032 synthetic, non-natural oligomers, we selected and characterized small molecules that mimic ZIKV epitopes. High-throughput fluorescence-activated cell sorter-based bead screening was used to select molecules that bound IgG from ZIKV-immune but not from dengue-immune sera. Deep sequencing of the DNA from the "Zika-only" beads identified 40 candidate molecular structures. A lead candidate small molecule "CZV1-1" was selected that correctly identifies serum specimens from Zika-experienced patients with good sensitivity and specificity (85.3% and 98.4%, respectively). Binding competition studies of purified anti-CZV1-1 IgG against known ZIKV-specific monoclonal antibodies (mAbs) showed that CZV1-1 mimics a nonlinear, neutralizing conformational epitope in the domain III of the ZIKV envelope. Purified anti-CZV1-1 IgG neutralized infection of ZIKV in cell cultures with potencies comparable to highly specific ZIKV-neutralizing mAbs. This study demonstrates an innovative approach for identification of synthetic non-natural molecular mimics of conformational virus epitopes. Such molecular mimics may have value in the development of accurate diagnostic assays for Zika, as well as for other viruses.

Seroprevalence of dengue, Japanese encephalitis and Zika among long-term expatriates in Thailand

BACKGROUND

Travel to Southeast Asia increases the likelihood of acquiring mosquito-borne Flavivirus infections such as dengue (DENV), Japanese encephalitis (JEV) and Zika viruses (ZIKV). Expatriates are long-term travellers who have a higher risk of mosquito-borne illness at their destination country. The purpose of this study was to evaluate the seroprevalence of DENV, JEV and ZIKV infections and the determinants contributing to seropositivity among expatriates living in Thailand.

METHODS

A cross-sectional study was performed from December 2017 to February 2020. Expatriates from non-Flavivirus endemic countries were recruited. 5 mL of blood was collected for DENV 1-4, JEV and ZIKV antibody testing by plaque reduction neutralization test (PRNT50). Individuals with vaccination histories or diagnoses for dengue, Japanese encephalitis, yellow fever and tick-borne encephalitis were excluded.

RESULTS

Among 254 participants, most participants (83.1%) were male, the mean age was 65 years and the median duration of stay in Thailand was 6 years. Seroprevalence rate of any Flavivirus, non-specific DENV, DENV1-4, JEV and ZIKV were 34.3, 30.7, 20.5, 18.1, 18.9, 10.6, 4.7 and 2.8%, respectively. The presence of neutralizing antibodies against DENV1-4 positively correlates with the duration of stay in Thailand. DENV seropositivity was associated with living in urban areas (aOR 2.75, 95% CI 1.36-5.57). Expatriates were unlikely to have detectable anti-JEV antibodies regardless of time spent in a JEV-endemic area. No risk factors were identified that were significantly associated with JEV or ZIKV seropositivity. Only 48.4% received pre-travel counselling services, while only 18.9% visited a travel medicine specialist.

CONCLUSIONS

A high proportion (34.3%) of long-term expatriates living in Thailand were seropositive for flavivirus, mainly from dengue (30.7%). To minimize risk, travel medicine practitioners should provide adequate pre-travel health risk information on mosquito-borne flavivirus infection and offer advice on mosquito bite prevention strategies. Dengue vaccine might be considered in high-risk travellers such as long-term expatriate.

Negevirus Piura Suppresses Zika Virus Replication in Mosquito Cells

We investigated the interaction between the insect-specific virus, Piura virus (PIUV), and the arbovirus Zika virus (ZIKV) in Aedes albopictus cells. We performed coinfection experiments in C6/36 cells. Piura virus (Cor 33 strain, Colombia) and ZIKV (PRVABC58 strain, Puerto Rico) were co-inoculated into C6/36 cells using two multiplicity of infection (MOI) combinations: 0.1 for both viruses and 1.0 for ZIKV, 0.1 for PIUV. Wells were infected in triplicate with either PIUV and ZIKV coinfection, ZIKV-only, or PIUV-only. Mock infected cells served as control wells. The cell suspension was collected daily 7 days post-infection. Zika virus load was titrated by TCID50 on Vero 76 cells. The ZIKV-only infection and PIUV and ZIKV coinfection experiments were also quantified by RT-qPCR. We also investigated whether ZIKV interfered in the PIUV replication. PIUV suppressed the replication of ZIKV, resulting in a 10,000-fold reduction in ZIKV titers within 3 days post-infection. PIUV viral loads were not reduced in the presence of ZIKV. We conclude that, when concurrently infected, PIUV suppresses ZIKV in C6/36 cells while ZIKV does not interfere in PIUV replication.

[Clinical efficiency and safety of riamilovir under various dosage regimens for treatment of acute respiratory viral infections in adults]

AIM

To evaluate the clinical efficacy and safety of antiviral drug riamilovir in patients with acute respiratory viral infections (ARVI) of non-coronavirus (SARS-CoV-2) etiology with different dosing regimens.

MATERIALS AND METHODS

The study included 150 patients with ARVI aged 18-27 years (50 patients received riamilovir in the regimen of 250 mg 3 times a day for 5 days, 50 patients received riamilovir in the off label regimen of 250 mg 5 times a day for 5 days, 50 patients received only pathogenetic treatment).

RESULTS

The use of riamilovir in both treatment regimens led to a reduction in the duration of inpatient treatment. The shortest periods of hospitalization were noted in patients who received the study drug at higher daily dosages. The use of riamilovir reduced the duration and severity of general infectious manifestations of the disease, while the shortest total duration of fever and a number of respiratory tract syndromes was registered among people who received riamilovir in the regimen of 1250 mg per day for 5 days, no adverse events were registered, additionally, 100% elimination of ARVI pathogens was noted in 1250 mg per day group.

CONCLUSION

Riamilovir has shown clinical efficacy and a good safety profile in in both treatment regimens. The dosage regimen of 1250 mg per day led to more significant clinical effects and to 100% elimination of ARVI pathogens in the study group by the 6th day of hospitalization.

Strain Variation Can Significantly Modulate the miRNA Response to Zika Virus Infection

Zika virus (ZIKV) is a mosquito-transmitted virus that has emerged as a major public health concern due to its association with neurological disorders in humans, including microcephaly in fetuses. ZIKV infection has been shown to alter the miRNA profile in host cells, and these changes can contain elements that are proviral, while others can be antiviral in action. In this study, the expression of 22 miRNAs in human A549 cells infected with two different ZIKV isolates was investigated. All of the investigated miRNAs showed significant changes in expression at at least one time point examined. Markedly, 18 of the miRNAs examined showed statistically significant differences in expression between the two strains examined. Four miRNAs (miR-21, miR-34a, miR-128 and miR-155) were subsequently selected for further investigation. These four miRNAs were shown to modulate antiviral effects against ZIKV, as downregulation of their expression through anti-miRNA oligonucleotides resulted in increased virus production, whereas their overexpression through miRNA mimics reduced virus production. However, statistically significant changes were again seen when comparing the two strains investigated. Lastly, candidate targets of the miRNAs miR-34a and miR-128 were examined at the level of the mRNA and protein. HSP70 was identified as a target of miR-34a, but, again, the effects were strain type-specific. The two ZIKV strains used in this study differ by only nine amino acids, and the results highlight that consideration must be given to strain type variation when examining the roles of miRNAs in ZIKV, and probably other virus infections.

Insights into the structure, functional perspective, and pathogenesis of ZIKV: an updated review

Zika virus (ZIKV) poses a serious threat to the entire world. The rapid spread of ZIKV and recent outbreaks since 2007 have caused worldwide concern about the virus. Diagnosis is complicated because of the cross-reactivity of the virus with other viral antibodies. Currently, the virus is diagnosed by molecular techniques such as RT-PCR and IgM-linked enzyme immunoassays (MAC-ELISA). Recently, outbreaks and epidemics have been caused by ZIKV, and severe clinical symptoms and congenital malformations have also been associated with the virus. Although most ZIKV infections present with a subclinical or moderate flu-like course of illness, severe symptoms such as Guillain-Barre syndrome in adults and microcephaly in children of infected mothers have also been reported. Because there is no reliable cure for ZIKV and no vaccine is available, the public health response has focused primarily on preventing infection, particularly in pregnant women. A comprehensive approach is urgently needed to combat this infection and stop its spread and imminent threat. In view of this, this review aims to present the current structural and functional viewpoints, structure, etiology, clinical prognosis, and measures to prevent this transmission based on the literature and current knowledge. Moreover, we provide thorough description of the current understanding about ZIKV interaction with receptors, and a comparative examination of its similarities and differences with other viruses.

Trends in ELISA-Based Flavivirus IgG Serosurveys: A Systematic Review

Flaviviruses include virus species that are major public health threats worldwide. To determine the immunity landscape of these viruses, seroprevalence studies are often performed using IgG ELISA, which is a simple and rapid alternative to the virus neutralization test. In this review, we aim to describe the trends in flavivirus IgG ELISA-based serosurveys. A systematic literature review using six databases was performed to collate cohort and cross-sectional studies performed on the general population. A total of 204 studies were included in this review. The results show that most studies were performed on dengue virus (DENV), whereas Japanese Encephalitis Virus (JEV) was the least studied. For geographic distribution, serosurveys followed known disease prevalence. Temporally, the number of serosurveys increased after outbreaks and epidemics except for JEV, for which studies were performed to demonstrate the effectiveness of vaccination campaigns. Commercial kits were more commonly used than in-house assays for DENV, West Nile Virus (WNV), and Zika virus (ZIKV). Overall, most studies employed an indirect ELISA format, and the choice of antigens varied per virus. This review shows that flavivirus epidemiology is related to the regional and temporal distribution of serosurveys. It also highlights that endemicity, cross-reactivities, and kit availabilities affect assay choice in serosurveys.