Geographic patterns of koala retrovirus genetic diversity, endogenization, and subtype distributions.

Koala retrovirus (KoRV) subtype A (KoRV-A) is currently in transition from exogenous virus to endogenous viral element, providing an ideal system to elucidate retroviral-host coevolution. We characterized KoRV geography using fecal DNA from 192 samples across 20 populations throughout the koala's range. We reveal an abrupt change in KoRV genetics and incidence at the Victoria/New South Wales state border. In northern koalas, pol gene copies were ubiquitously present at above five per cell, consistent with endogenous KoRV. In southern koalas, pol copies were detected in only 25.8% of koalas and always at copy numbers below one, while the env gene was detected in all animals and in a majority at copy numbers above one per cell. These results suggest that southern koalas carry partial endogenous KoRV-like sequences. Deep sequencing of the env hypervariable region revealed three putatively endogenous KoRV-A sequences in northern koalas and a single, distinct sequence present in all southern koalas. Among northern populations, env sequence diversity decreased with distance from the equator, suggesting infectious KoRV-A invaded the koala genome in northern Australia and then spread south. The exogenous KoRV subtypes (B to K), two novel subtypes, and intermediate subtypes were detected in all northern koala populations but were strikingly absent from all southern animals tested. Apart from KoRV subtype D, these exogenous subtypes were generally locally prevalent but geographically restricted, producing KoRV genetic differentiation among northern populations. This suggests that sporadic evolution and local transmission of the exogenous subtypes have occurred within northern Australia, but this has not extended into animals within southern Australia.

The role of N-glycosylation in spike antigenicity for the SARS-CoV-2 gamma variant.

The emergence of SARS-CoV-2 variants alters the efficacy of existing immunity towards the viral spike protein, whether acquired from infection or vaccination. Mutations that impact N-glycosylation of spike may be particularly important in influencing antigenicity, but their consequences are difficult to predict. Here, we compare the glycosylation profiles and antigenicity of recombinant viral spike of ancestral Wu-1 and the Gamma strain, which has two additional N-glycosylation sites due to amino acid substitutions in the N-terminal domain (NTD). We found that a mutation at residue 20 from threonine to asparagine within the NTD caused the loss of NTD-specific antibody COVA2-17 binding. Glycan site-occupancy analyses revealed that the mutation resulted in N-glycosylation switching to the new sequon at N20 from the native N17 site. Site-specific glycosylation profiles demonstrated distinct glycoform differences between Wu-1, Gamma, and selected NTD variant spike proteins, but these did not affect antibody binding. Finally, we evaluated the specificity of spike proteins against convalescent COVID-19 sera and found reduced cross-reactivity against some mutants, but not Gamma spike compared to Wuhan spike. Our results illustrate the impact of viral divergence on spike glycosylation and SARS-CoV-2 antibody binding profiles.

Enhancement of cellular immunity following needle-free vaccination of mice with SARS-CoV-2 spike protein.

The COVID-19 pandemic has highlighted the need for vaccines capable of providing rapid and robust protection. One way to improve vaccine efficacy is delivery via microarray patches, such as the Vaxxas high-density microarray patch (HD-MAP). We have previously demonstrated that delivery of a SARS-CoV-2 protein vaccine candidate, HexaPro, via the HD-MAP induces potent humoral immune responses. Here, we investigate the cellular responses induced by HexaPro HD-MAP vaccination. We found that delivery via the HD-MAP induces a type one biassed cellular response of much greater magnitude as compared to standard intramuscular immunization.

SARS-CoV-2 drives NLRP3 inflammasome activation in human microglia through spike protein.

Coronavirus disease-2019 (COVID-19) is primarily a respiratory disease, however, an increasing number of reports indicate that SARS-CoV-2 infection can also cause severe neurological manifestations, including precipitating cases of probable Parkinson's disease. As microglial NLRP3 inflammasome activation is a major driver of neurodegeneration, here we interrogated whether SARS-CoV-2 can promote microglial NLRP3 inflammasome activation. Using SARS-CoV-2 infection of transgenic mice expressing human angiotensin-converting enzyme 2 (hACE2) as a COVID-19 pre-clinical model, we established the presence of virus in the brain together with microglial activation and NLRP3 inflammasome upregulation in comparison to uninfected mice. Next, utilising a model of human monocyte-derived microglia, we identified that SARS-CoV-2 isolates can bind and enter human microglia in the absence of viral replication. This interaction of virus and microglia directly induced robust inflammasome activation, even in the absence of another priming signal. Mechanistically, we demonstrated that purified SARS-CoV-2 spike glycoprotein activated the NLRP3 inflammasome in LPS-primed microglia, in a ACE2-dependent manner. Spike protein also could prime the inflammasome in microglia through NF-κB signalling, allowing for activation through either ATP, nigericin or α-synuclein. Notably, SARS-CoV-2 and spike protein-mediated microglial inflammasome activation was significantly enhanced in the presence of α-synuclein fibrils and was entirely ablated by NLRP3-inhibition. Finally, we demonstrate SARS-CoV-2 infected hACE2 mice treated orally post-infection with the NLRP3 inhibitory drug MCC950, have significantly reduced microglial inflammasome activation, and increased survival in comparison with untreated SARS-CoV-2 infected mice. These results support a possible mechanism of microglial innate immune activation by SARS-CoV-2, which could explain the increased vulnerability to developing neurological symptoms akin to Parkinson's disease in COVID-19 infected individuals, and a potential therapeutic avenue for intervention.

Koala retrovirus genetic diversity and transmission dynamics within captive koala populations.

Koala populations are currently in rapid decline across Australia, with infectious diseases being a contributing cause. The koala retrovirus (KoRV) is a gammaretrovirus present in both captive and wild koala colonies that presents an additional challenge for koala conservation in addition to habitat loss, climate change, and other factors. Currently, nine different subtypes (A to I) have been identified; however, KoRV genetic diversity analyses have been limited. KoRV is thought to be exogenously transmitted between individuals, with KoRV-A also being endogenous and transmitted through the germline. The mechanisms of exogenous KoRV transmission are yet to be extensively investigated. Here, deep sequencing was employed on 109 captive koalas of known pedigree, housed in two institutions from Southeast Queensland, to provide a detailed analysis of KoRV transmission dynamics and genetic diversity. The final dataset included 421 unique KoRV sequences, along with the finding of an additional subtype (KoRV-K). Our analysis suggests that exogenous transmission of KoRV occurs primarily between dam and joey, with evidence provided for multiple subtypes, including nonendogenized KoRV-A. No evidence of sexual transmission was observed, with mating partners found to share a similar number of sequences as unrelated koala pairs. Importantly, both distinct captive colonies showed similar trends. These findings indicate that breeding strategies or antiretroviral treatment of females could be employed as effective management approaches in combating KoRV transmission.

Oncological outcomes of visibly complete transurethral resection prior to neoadjuvant chemotherapy for bladder cancer.

PURPOSE: To evaluate the potential oncologic benefit of a visibly complete transurethral resection of a bladder tumor (TURBT) prior to neoadjuvant chemotherapy (NAC) and radical cystectomy (RC). MATERIALS AND METHODS: We identified patients who received NAC and RC between 2011-2021. Records were reviewed to assess TURBT completeness. The primary outcome was pathologic downstaging (

Micro-fusion inhibition tests: quantifying antibody neutralization of virus-mediated cell-cell fusion.

Although enveloped viruses canonically mediate particle entry through virus-cell fusion, certain viruses can spread by cell-cell fusion, brought about by receptor engagement and triggering of membrane-bound, viral-encoded fusion proteins on the surface of cells. The formation of pathogenic syncytia or multinucleated cells is seen in vivo, but their contribution to viral pathogenesis is poorly understood. For the negative-strand paramyxoviruses respiratory syncytial virus (RSV) and Nipah virus (NiV), cell-cell spread is highly efficient because their oligomeric fusion protein complexes are active at neutral pH. The recently emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has also been reported to induce syncytia formation in infected cells, with the spike protein initiating cell-cell fusion. Whilst it is well established that fusion protein-specific antibodies can block particle attachment and/or entry into the cell (canonical virus neutralization), their capacity to inhibit cell-cell fusion and the consequences of this neutralization for the control of infection are not well characterized, in part because of the lack of specific tools to assay and quantify this activity. Using an adapted bimolecular fluorescence complementation assay, based on a split GFP-Renilla luciferase reporter, we have established a micro-fusion inhibition test (mFIT) that allows the identification and quantification of these neutralizing antibodies. This assay has been optimized for high-throughput use and its applicability has been demonstrated by screening monoclonal antibody (mAb)-mediated inhibition of RSV and NiV fusion and, separately, the development of fusion-inhibitory antibodies following NiV vaccine immunization in pigs. In light of the recent emergence of coronavirus disease 2019 (COVID-19), a similar assay was developed for SARS-CoV-2 and used to screen mAbs and convalescent patient plasma for fusion-inhibitory antibodies. Using mFITs to assess antibody responses following natural infection or vaccination is favourable, as this assay can be performed entirely at low biocontainment, without the need for live virus. In addition, the repertoire of antibodies that inhibit cell-cell fusion may be different to those that inhibit particle entry, shedding light on the mechanisms underpinning antibody-mediated neutralization of viral spread.

Intra-host growth kinetics of dengue virus in the mosquito Aedes aegypti.

Dengue virus (DENV) transmission by mosquitoes is a time-dependent process that begins with the consumption of an infectious blood-meal. DENV infection then proceeds stepwise through the mosquito from the midgut to the carcass, and ultimately to the salivary glands, where it is secreted into saliva and then transmitted anew on a subsequent bite. We examined viral kinetics in tissues of the Aedes aegypti mosquito over a finely graded time course, and as per previous studies, found that initial viral dose and serotype strain diversity control infectivity. We also found that a threshold level of virus is required to establish body-wide infections and that replication kinetics in the early and intermediate tissues do not predict those of the salivary glands. Our findings have implications for mosquito GMO design, modeling the contribution of transmission to vector competence and the role of mosquito kinetics in the overall DENV epidemiological landscape.

Assessing the potential of unmanned aerial vehicle spraying of aqueous ozone as an outdoor disinfectant for SARS-CoV-2.

The COVID-19 pandemic has revealed gaps in our understanding of safe, effective and efficient means of disinfecting high use public spaces. Whilst this creates an opportunity for development and application of innovative approaches such as unmanned aerial vehicle (UAV) based disinfection, unregulated outdoor disinfection using chlorine has led to environmental and public health risks. This study has quantified the efficiency, safety and efficacy of UAV-based spraying of aqueous ozone. Optimised UAV flight characteristics of 4.7 km/h at 1.7 m elevation spraying 2.4 L/min were able to provide >97% and >92% coverage of a 1 m and 2 m wide swath respectively. During spraying operations using 1 mg/L aqueous ozone, atmospheric concentrations of ozone remained within background levels (<0.04 ppm). Highly efficient inactivation of two different isolates of SARS-CoV-2 virus was achieved at aqueous ozone concentrations of 0.75 mg/L after an incubation period of only 5 min, with 0.375 mg/L achieving 82-91.5% inactivation in this time. Exposure of diamondback moth larvae and parasitic wasps to 1 mg/L aqueous ozone did not significantly affect their survivorship. These results indicate for the first time that aqueous ozone may provide the required balance between human and environmental safety and viral inactivation efficacy for targeted application in high risk outdoor settings.

Degradation and remobilization of endogenous retroviruses by recombination during the earliest stages of a germ-line invasion.

Endogenous retroviruses (ERVs) are proviral sequences that result from colonization of the host germ line by exogenous retroviruses. The majority of ERVs represent defective retroviral copies. However, for most ERVs, endogenization occurred millions of years ago, obscuring the stages by which ERVs become defective and the changes in both virus and host important to the process. The koala retrovirus, KoRV, only recently began invading the germ line of the koala (Phascolarctos cinereus), permitting analysis of retroviral endogenization on a prospective basis. Here, we report that recombination with host genomic elements disrupts retroviruses during the earliest stages of germ-line invasion. One type of recombinant, designated recKoRV1, was formed by recombination of KoRV with an older degraded retroelement. Many genomic copies of recKoRV1 were detected across koalas. The prevalence of recKoRV1 was higher in northern than in southern Australian koalas, as is the case for KoRV, with differences in recKoRV1 prevalence, but not KoRV prevalence, between inland and coastal New South Wales. At least 15 additional different recombination events between KoRV and the older endogenous retroelement generated distinct recKoRVs with different geographic distributions. All of the identified recombinant viruses appear to have arisen independently and have highly disrupted ORFs, which suggests that recombination with existing degraded endogenous retroelements may be a means by which replication-competent ERVs that enter the germ line are degraded.

Analysis of phylogenetic diversity and in vitro adherence characteristics of respiratory syncytial virus and Streptococcus pneumoniae clinical isolates obtained during pediatric respiratory co-infections.

Respiratory syncytial virus (RSV) and Streptococcus pneumoniae are frequently co-associated during acute respiratory infections, particularly amongst infants and young children. In this study, we aimed to identify strains of RSV and serotypes/sequence types of S. pneumoniae associated with co-infections within a cohort of paediatric patients, and to assess RSV-mediated adhesion of pneumococcal isolates. The RSV glycoprotein sequence was determined for 58 RSV-positive samples and molecular serotyping and MLST was used to analyse 26 pneumococcal isolates. We also compared 23 pneumococcal isolates for their adherence to RSV-infected or mock-infected airway epithelia cells using immunofluorescence microscopy and automated particle counting. The tight association between RSV and S. pneumoniae was also visualized using scanning electron microscopy. This study did not identify any statistically significant trend in the strains of RSV and S. pneumoniae associated with co-infections. Furthermore, almost all isolates (22 of 23) showed significantly increased adherence to RSV-infected cells. The level of adherence did not appear to correlate with pneumococcal strain or sequence type, and isolates obtained from RSV-infected patients displayed a similar level of adherence as those from RSV-negative patients. The absence of particular S. pneumoniae or RSV strains associated with co-infection, together with the near ubiquitous presence of RSV-mediated adhesion throughout the pneumococcal clinical isolates, may indicate that the mechanisms governing the association with RSV are of sufficient importance to be maintained across much of the species.

Inactivation of Japanese encephalitis virus in plasma by methylene blue combined with visible light and in platelet concentrates by ultraviolet C light.

Japanese encephalitis virus (JEV) is endemic to tropical areas in Asia and the Western Pacific. It can cause fatal encephalitis, although most infected individuals are asymptomatic. JEV is mainly transmitted to humans through the bite of an infected mosquito, but can also be transmitted through blood transfusion. To manage the potential risk of transfusion transmission, pathogen inactivation (PI) technologies, such as THERAFLEX MB-Plasma and THERAFLEX UV-Platelets systems, have been developed. We examined the efficacy of these two PI systems to inactivate JEV. STUDY DESIGN AND METHODS: Japanese encephalitis virus-spiked plasma units were treated using the THERAFLEX MB-Plasma system (visible light doses, 20, 40, 60, and 120 [standard] J/cm2) in the presence of methylene blue at approximately 0.8 µmol/L and spiked platelet concentrates (PCs) were treated using the THERAFLEX UV-Platelets system (UVC doses, 0.05, 0.10, 0.15, and 0.20 [standard] J/cm2). Samples were taken before the first and after each illumination dose and tested for infectivity using an immunoplaque assay. RESULTS: Treatment of plasma with the THERAFLEX MB-Plasma system resulted in an average of 6.59 log reduction in JEV infectivity at one-sixth of the standard visible light dose (20 J/cm2). For PCs, treatment with the THERAFLEX UV-Platelet system resulted in an average of 7.02 log reduction in JEV infectivity at the standard UVC dose (0.20 J/cm2). CONCLUSIONS: The THERAFLEX MB-Plasma and THERAFLEX UV-Platelets systems effectively inactivated JEV in plasma or PCs, and thus these PI technologies could be an effective option to reduce the risk of JEV transfusion transmission.

The Heptad Repeat C Domain of the Respiratory Syncytial Virus Fusion Protein Plays a Key Role in Membrane Fusion.

Respiratory syncytial virus (RSV) mediates host cell entry through the fusion (F) protein, which undergoes a conformational change to facilitate the merger of viral and host lipid membrane envelopes. The RSV F protein comprises a trimer of disulfide-bonded F1 and F2 subunits that is present on the virion surface in a metastable prefusion state. This prefusion form is readily triggered to undergo refolding to bring two heptad repeats (heptad repeat A [HRA] and HRB) into close proximity to form a six-helix bundle that stabilizes the postfusion form and provides the free energy required for membrane fusion. This process can be triggered independently of other proteins. Here, we have performed a comprehensive analysis of a third heptad repeat region, HRC (amino acids 75 to 97), an amphipathic α-helix that lies at the interface of the prefusion F trimer and is a major structural feature of the F2 subunit. We performed alanine scanning mutagenesis from Lys-75 to Met-97 and assessed all mutations in transient cell culture for expression, proteolytic processing, cell surface localization, protein conformation, and membrane fusion. Functional characterization revealed a striking distribution of activity in which fusion-increasing mutations localized to one side of the helical face, while fusion-decreasing mutations clustered on the opposing face. Here, we propose a model in which HRC plays a stabilizing role within the globular head for the prefusion F trimer and is potentially involved in the early events of triggering, prompting fusion peptide release and transition into the postfusion state.IMPORTANCE RSV is recognized as the most important viral pathogen among pediatric populations worldwide, yet no vaccine or widely available therapeutic treatment is available. The F protein is critical for the viral replication process and is the major target for neutralizing antibodies. Recent years have seen the development of prefusion stabilized F protein-based approaches to vaccine design. A detailed understanding of the specific domains and residues that contribute to protein stability and fusion function is fundamental to such efforts. Here, we present a comprehensive mutagenesis-based study of a region of the RSV F2 subunit (amino acids 75 to 97), referred to as HRC, and propose a role for this helical region in maintaining the delicate stability of the prefusion form.

Stachyonic Acid: A Dengue Virus Inhibitor from Basilicum polystachyon.

Stachyonic acid A, arising from the first in-depth phytochemical investigation of the herb Basilicum polystachyon, was found to display potent inhibitory activity against dengue virus, with limited cytotoxicity. Andrographolide, a known dengue virus inhibitor and closely related labdane-type diterpene, is structurally more complex but displayed poor antiviral activity in the PRNT assay, and increased cytotoxicity in comparison. Furthermore, a Diels-Alder reaction with PTAD identified the active pharmacophore of stachyonic acid to be the conjugated diene.

Inactivation of yellow fever virus in plasma after treatment with methylene blue and visible light and in platelet concentrates following treatment with ultraviolet C light.

BACKGROUND: Yellow fever virus (YFV) is endemic to tropical and subtropical areas in South America and Africa, and is currently a major public health threat in Brazil. Transfusion transmission of the yellow fever vaccine virus has been demonstrated, which is indicative of the potential for viral transfusion transmission. An approach to manage the potential YFV transfusion transmission risk is the use of pathogen inactivation (PI) technology systems, such as THERAFLEX MB-Plasma and THERAFLEX UV-Platelets (Macopharma). We aimed to investigate the efficacy of these PI technology systems to inactivate YFV in plasma or platelet concentrates (PCs). STUDY DESIGN AND METHODS: YFV spiked plasma units were treated using THERAFLEX MB-Plasma system (visible light doses: 20, 40, 60, and 120 [standard] J/cm2 ) in the presence of methylene blue (approx. 0.8 µmol/L) and spiked PCs were treated using THERAFLEX UV-Platelets system (ultraviolet C doses: 0.05, 0.10, 0.15, and 0.20 [standard] J/cm2 ). Samples were taken before the first and after each illumination dose and tested for residual virus using a modified plaque assay. RESULTS: YFV infectivity was reduced by an average of 4.77 log or greater in plasma treated with the THERAFLEX MB-Plasma system and by 4.8 log or greater in PCs treated with THERAFLEX UV-Platelets system. CONCLUSIONS: Our study suggests the THERAFLEX MB-Plasma and the THERAFLEX UV-Platelets systems can efficiently inactivate YFV in plasma or PCs to a similar degree as that for other arboviruses. Given the reduction levels observed in this study, these PI technology systems could be an effective option for managing YFV transfusion-transmission risk in plasma and PCs.

Antibody-Binding, Antifouling Surface Coatings Based on Recombinant Expression of Zwitterionic EK Peptides.

Development of antifouling films which selectively capture or target proteins of interest is essential for controlling interactions at the "bio/nano" interface. However, in order to synthesize biofunctional films from synthetic polymers that incorporate chemical "motifs" for surface immobilization, antifouling, and oriented biomolecule attachment, multiple reaction steps need to be carried out at the solid/liquid interface. EKx is a zwitterionic peptide that has previously been shown to have excellent antifouling properties. In this study, we recombinantly expressed EKx peptides and genetically encoded both surface attachment and antibody-binding motifs, before characterizing the resultant biopolymers by traditional methods. These peptides were then immobilized to organosilica nanoparticles for binding IgG, and subsequently capturing dengue NS1 as a model antigen from serum-containing solution. We found that a mixed layer of a short peptide (4.9 kDa) "backfilled" with a longer peptide terminated with an IgG-binding Z-domain (18 kDa) demonstrated selective capture of dengue NS1 protein down to ∼10 ng mL-1 in either PBS or 20% serum.

Basimarols A, B, and C, Highly Oxygenated Pimarane Diterpenoids from Basilicum polystachyon.

The highly oxygenated pimarane diterpenoids basimarols A, B, and C (3-5) were isolated from the plant species Basilicum polystachyon, which was collected within the Australian arid zone. Structure elucidation was performed using a suite of spectroscopic techniques, including X-ray crystallography. Anticancer and anti-DENV activity of 3-5 was explored, but only limited activity was observed. More extensive antiviral evaluation of stachyonic acid A (1), which was also isolated from B. polystachyon, revealed broad spectrum antiviral activity against West Nile virus (Kunjin strain, WNVKun) and human influenza viruses H1N1 and H3N2.

Complete genome of Aedes aegypti anphevirus in the Aag2 mosquito cell line.

A novel negative-sense RNA virus, Aedes aegypti anphevirus, was recently identified in wild Aedes aegypti mosquitoes. We show that this virus is also present in the Aag2 Aedes aegypti cell line and characterize its complete genome and evolutionary history. The Aedes aegypti anphevirus genome is estimated to be 12 916 nucleotides in length, contains four genes and has a genome structure similar to that of other anpheviruses. Phylogenetically, Aedes aegypti anphevirus falls within an unclassified group of insect-specific viruses in the order Mononegavirales that form a sister-group to the chuviruses. Notably, the Aag2 cell line used here was also experimentally infected with dengue virus and naturally contained a Phasi Charoen-like virus and cell-fusing agent virus. All four viruses were at relatively high abundance, with 0.5 % of sequence reads assigned to Aedes aegypti anphevirus. The Aag2 cell line is therefore permissive to efficient co-infection with dengue virus and multiple insect-specific viruses.

Streptococcus pneumoniae colonization of the nasopharynx is associated with increased severity during respiratory syncytial virus infection in young children.

BACKGROUND AND OBJECTIVE: Respiratory syncytial virus (RSV) is the most significant cause of acute respiratory infection (ARI) in early life. RSV and other respiratory viruses are known to stimulate substantial outgrowth of potentially pathogenic bacteria in the upper airways of young children. However, the clinical significance of interactions between viruses and bacteria is currently unclear. The present study aimed to clarify the effect of viral and bacterial co-detections on disease severity during paediatric ARI. METHODS: Nasopharyngeal aspirates from children under 2 years of age presenting with ARI to the emergency department were screened by quantitative PCR for 17 respiratory viruses and the bacterial pathogens Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Associations between pathogen detection and clinical measures of disease severity were investigated. RESULTS: RSV was the most common virus detected, present in 29 of 58 samples from children with ARI (50%). Detection of S. pneumoniae was significantly more frequent during RSV infections compared to other respiratory viruses (adjusted effect size: 1.8, P: 0.03), and co-detection of both pathogens was associated with higher clinical disease severity scores (adjusted effect size: 1.2, P: 0.03). CONCLUSION: Co-detection of RSV and S. pneumoniae in the nasopharynx was associated with more severe ARI, suggesting that S. pneumoniae colonization plays a pathogenic role in young children.

Arboviruses: A Family on the Move.

Arboviruses are a diverse group of vector-borne viruses, many of whose members are the cause of significant human morbidity and mortality. Over the last 30 years, the emergence and/or resurgence of arboviruses have posed a considerable global health threat. The ongoing geographical expansion of the dengue viruses (DENV), along with the explosive outbreaks of West Nile virus (WNV), Chikungunya virus (CHIKV) and more recently, Zika virus (ZIKV) have all served as reminders that new epidemics may emerge at any time from this diversity. A clearer understanding of what mechanisms drive these dramatic changes in vector-host transmission cycles that result in the human population becoming significantly more exposed, will help to prepare us for the next emerging epidemic/pandemic. This Chapter seeks to provide a brief overview of the arboviruses, their mode of transmission and some of the known factors that drive their expansion.