Surveillance of Zika virus infection in the EU/EEA, June 2015 to January 2017

Assessment of the Risk of Exotic Zika Virus Strain Transmission by Aedes aegypti and Culex quinquefasciatus from Senegal Compared to a Native Strain

Zika virus (ZIKV) shows an enigmatic epidemiological profile in Africa. Despite its frequent detection in mosquitoes, few human cases have been reported. This could be due to the low infectious potential or low virulence of African ZIKV lineages. This study sought to assess the susceptibility of A. aegypti and C. quinquefasciatus to ZIKV strains from Senegal, Brazil, and New Caledonia. Vertical transmission was also investigated. Whole bodies, legs/wings and saliva samples were tested for ZIKV by real-time PCR to estimate infection, dissemination and transmission rates as well as the infection rate in the progeny of infected female A. aegypti. For A. aegypti, the Senegalese strain showed at 15 days post-exposure (dpe) a significantly higher infection rate (52.43%) than the Brazilian (10%) and New Caledonian (0%) strains. The Brazilian and Senegalese strains were disseminated but not detected in saliva. No A. aegypti offspring from females infected with Senegalese and Brazilian ZIKV strains tested positive. No infection was recorded for C. quinquefasciatus. We observed the incompetence of Senegalese A. aegypti to transmit ZIKV and the C. quinquefasciatus were completely refractory. The effect of freezing ZIKV had no significant impact on the vector competence of Aedes aegypti from Senegal, and vertical transmission was not reported in this study.

The threat of mosquito-borne arboviral disease in Spain: A bibliographic review

Over the last two decades there has been an increase in outbreaks of arboviral diseases, being Spain at high risk for disease emergence. This paper reviews the current evidence regarding the transmissibility, disease epidemiology, control strategies and mosquito-borne disease drivers and maintaining factors in Spain. There is risk of autochthonous cases and outbreaks in Spain due to recent transmission occurrence. Recently, there has been an expansion of Aedes Albopticus, a vector for Dengue, Zika and Chikungunya; and Cullex spp., vector for West Nile Virus, already endemic in Spain. Their establishment has been facilitated by climate and environmental drivers. If climate change projections are to be met, an increase in disease transmission is to be expected, as well as the re-establishment of other vectors such as Aedes Aegypti. Our review supports the need to understand the threat of these emerging diseases and implement preventive strategies in order to minimise their impact.

Clinicopathologic features among different viral epidemic outbreaks involving the skin

The current coronavirus disease 2019 pandemic has exceeded any epidemiologic prevision, but increasing information suggests some analogies with the major viral outbreaks in the last century, and a general warning has been issued on the possibility that coinfections can make the differential diagnosis and treatment difficult, especially in tropical countries. Some reports have noted that the presence of high dengue antibodies can give a false-negative result when testing for severe acute respiratory syndrome coronavirus 2. Mucocutaneous manifestations are very frequent, with an apparent overlap among different pathogens. However, strong clinicopathologic correlation might provide some clues to address differentials. Waiting for laboratory and instrumental results, the timing and distribution of skin lesions is often pathognomonic. Histopathologic findings characterize certain reaction patterns and provide insights on pathogenetic mechanisms. Unfortunately, skin assessment, especially invasive examinations such as biopsy, takes a back seat in severely ill patients. A literature retrieval was performed to collect information from other epidemics to counteract what has become the most frightening disease of our time.

Clinicopathologic features between different viral epidemic outbreaks involving the skin

The current coronavirus disease 2019 pandemic has exceeded any epidemiologic prevision, but increasing information suggests some analogies with the major viral outbreaks of the last century. A general warning has been issued on the possibility that coinfections can make differential diagnosis and treatment difficult, especially in tropical countries. Some reports have pointed out that the presence of high Dengue antibodies can give a false-negative result for severe acute respiratory syndrome coronavirus 2. Mucocutaneous manifestations are very frequent, with an apparent overlap among different pathogens. A strong clinicopathologic correlation, however, may provide some clues to address the differential. Waiting for laboratory and instrumental results, the timing and distribution of skin lesions is often pathognomonic. Histopathologic findings characterize certain reaction patterns and provide insights on pathogenetic mechanisms. Unfortunately, skin assessments, especially invasive exams such as biopsy, are less important in severely ill patients. A literature review was performed to collect information from other epidemics to counteract what has become the most frightening disease of our time.

Infectious disease surveillance system descriptors: proposal for a comprehensive set

To tailor a surveillance system to its objectives and to evaluate its fitness for purpose, an accurate description of its structural elements is essential. Existing recommendations for setting up a system seldom offer a comprehensive list of all surveillance elements to be considered. Moreover, there is sometimes confusion in the way terms describing these elements are interpreted. The objective of this paper is to propose a comprehensive set of surveillance system descriptors that can delineate the important elements and clarify the meaning of the terms used. We identified 20 descriptors that we classified in five categories: (i) surveillance scheme; (ii) population and cases; (iii) supplementary data; (iv) information flow; and (v) period of time. We tried to make the definitions of these descriptors as clear and simple as possible to avoid confusion or misinterpretation of the terms used. The relative importance of each element may vary depending on the objectives of the surveillance scheme. Surveillance descriptors should be reviewed periodically to document changes and to assess if the system continues to be fit for purpose. Together with the minimum requirements for variables and the planned outputs for disseminating the data, the surveillance descriptors can be used to define surveillance standards.

The recently introduced Aedes albopictus in Tunisia has the potential to transmit chikungunya, dengue and Zika viruses

The mosquito Aedes albopictus was detected for the first time in Tunisia in 2018. With its establishment in the capital city of Tunis, local health authorities fear the introduction of new human arboviral diseases, like what happened in Europe with unexpected local cases of chikungunya, dengue and Zika. Even though this mosquito is competent to transmit the arboviruses mentioned above, the transmission level will vary depending on the couple, mosquito population and virus genotype. Here, we assessed the vector competence of Ae. albopictus Tunisia by experimental infections with chikungunya (CHIKV), dengue (DENV), and Zika (ZIKV) viruses. We found that Ae. albopictus Tunisia was highly competent for CHIKV (transmission efficiency of 25% at 21 post-infection) and to a lesser extent, for ZIKV (8.7%) and DENV (8.3%). Virus was detected in mosquito saliva at day 3 (CHIKV), day 10 (ZIKV) and day 21 (DENV) post-infection. These results suggest that the risk of emergence of chikungunya is the highest imposing a more sustained surveillance to limit Ae. albopictus populations in densely populated urban dwellings and at the entry points of travelers returning from CHIKV-endemic regions.

Vector-borne transmission of Zika virus in Europe, southern France, August 2019

On 1 October 2019, a locally-acquired Zika virus disease case was laboratory confirmed in Hyères, Var department. Active case finding identified two additional locally-acquired cases living within 90 m, with symptom onset 8 days before the index case. Extensive patient interviews did not yield information supporting transmission through sexual contact or substances of human origin. Vector-borne transmission by local Aedes albopictus mosquitoes is the most likely mode of transmission. Here we describe the public health response.

Performance of an Automated Zika IgG Immunoassay in the Detection of Zika IgG Specific Antibodies—A Validation Approach in Samples from Prevalence Areas and Non-Endemic Countries

The diagnosis of Zika virus infection is complicated and includes testing for nucleic acids and IgM and IgG antibodies, depending on the stage of infection. Zika IgG is an important marker of infection after the acute stage; however, IgG assays can lack specificity due to the similarities between Zika and other flaviviruses. In this study, the diagnostic sensitivity and specificity of the Elecsys^® Zika IgG assay were assessed in 496 samples from Zika endemic regions, and specificity only was assessed in 1685 blood screening and diagnostic samples from Zika non-endemic regions. Cross-reactivity was also assessed against a panel of 202 potentially cross-reacting samples. The performance of the Elecsys^® Zika IgG assay was compared with the anti-Zika virus ELISA IgG. In the samples from the Zika endemic regions, the Elecsys^® Zika IgG assay had 92.88% (95% confidence interval 89.42–95.48) sensitivity and 100% specificity and in the samples from Europe the Elecsys^® Zika IgG assay specificity was ≥99.62%. The Elecsys^® Zika IgG assay was highly specific in samples from both prevalent and non-endemic regions.

Importation of dengue, Zika and chikungunya infections in Europe: the current situation in Greece

Although several arboviruses-such as dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) viruses-are not endemic in Europe, they have the potential to emerge following importation of the virus, taking advantage of the favourable climate and ecosystem. DENV, ZIKV and CHIKV are transmitted by Aedes species mosquitoes and are amongst the most common travel-associated arboviruses. Furthermore, they are linked to sporadic, local outbreaks, especially in the southern parts of Europe. In this review we present in brief the DENV, ZIKV and CHIKV cases imported to Greece during the last 6 years (2013-2018), and we describe the recent laboratory data obtained from the Hellenic Pasteur Institute and the National Reference Centre for Arboviruses. We report 21 imported cases of DENV, ZIKV and CHIKV infections in travellers arriving in Greece. The probable origins were south-eastern Asian (71%) and north-central American (29%) countries. Furthermore, we stress the importance of early and accurate diagnosis in spite of a plethora of diagnostic challenges that clinicians and virologists have to face. Altogether, with the authorities' awareness and the preventive measures to be applied, local transmission events can be successfully avoided, especially in summer when the temperature is favourable for mosquito-borne infections.

Defeat Dengue and Zika Viruses With a One-Two Punch of Vaccine and Vector Blockade

Dengue virus (DENV) and Zika virus (ZIKV) are two mosquito-borne flaviviruses afflicting nearly half of the world population. Human infection by these viruses can either be asymptomatic or manifest as clinical diseases from mild to severe. Despite more cases are presented as self-limiting febrile illness, severe dengue disease can be manifested as hemorrhagic fever and hemorrhagic shock syndrome, and ZIKV infection has been linked to increased incidence of peripheral neuropathy Guillain-Barre syndrome and central neural disease such as microcephaly. The current prevention and treatment of these infectious diseases are either non-satisfactory or entirely lacking. Because DENV and ZIKV have much similarities in genomic and structural features, almost identical mode of mosquito-mediated transmission, and probably the same pattern of host innate and adaptive immunity toward them, it is reasonable and often desirable to investigate these two viruses side-by-side, and thereby devise common countermeasures against both. Here, we review the existing knowledge on DENV and ZIKV regarding epidemiology, molecular virology, protective immunity and vaccine development, discuss recent new discoveries on the functions of flavivirus NS1 protein in viral pathogenesis and transmission, and propose a one-two punch strategy using vaccine and vector blockade to overcome antibody-dependent enhancement and defeat Dengue and Zika viruses.

Using species distribution models to predict potential hot-spots for Rift Valley Fever establishment in the United Kingdom

Vector borne diseases are a continuing global threat to both human and animal health. The ability of vectors such as mosquitos to cover large distances and cross country borders undetected provide an ever-present threat of pathogen spread. Many diseases can infect multiple vector species, such that even if the climate is not hospitable for an invasive species, indigenous species may be susceptible and capable of transmission such that one incursion event could lead to disease establishment in these species. Here we present a consensus modelling methodology to estimate the habitat suitability for presence of mosquito species in the UK deemed competent for Rift Valley fever virus (RVF) and demonstrate its application in an assessment of the relative risk of establishment of RVF virus in the UK livestock population. The consensus model utilises observed UK mosquito surveillance data, along with climatic and geographic prediction variables, to inform six independent species distribution models; the results of which are combined to produce a single prediction map. As a livestock host is needed to transmit RVF, we then combine the consensus model output with existing maps of sheep and cattle density to predict the areas of the UK where disease is most likely to establish in local mosquito populations. The model results suggest areas of high suitability for RVF competent mosquito species across the length and breadth of the UK. Notable areas of high suitability were the South West of England and coastal areas of Wales, the latter of which was subsequently predicted to be at higher risk for establishment of RVF due to higher livestock densities. This study demonstrates the applicability of outputs of species distribution models to help predict hot-spots for risk of disease establishment. While there is still uncertainty associated with the outputs we believe that the predictions are an improvement on just using the raw presence points from a database alone. The outputs can also be used as part of a multidisciplinary approach to inform risk based disease surveillance activities.

Characteristics of Zika virus infection among international travelers: A prospective study from a Spanish referral unit

BACKGROUND

From the first Zika virus (ZIKV) description, it has progressively widespread worldwide. We analyzed demographic, clinical, microbiologic and travel-related characteristic from returned patients from a ZIKV endemic country in a referral Tropical Medicine Unit.

METHOD

A prospective cohort study performed in a Spanish referral center with the aim of determining the significant factors associated with confirmed Zika virus (ZIKV) infection.

RESULTS

817 patients, (56% women, median age 36 [IQR, Interquartile Range: 32-42]) were enrolled. Most had returned from Latin America (n = 486; 59.4%), travelled for tourism (n = 404; 49.4%) and stayed a median of 18 days (IQR: 10-30). 602 (73.6%) presented symptoms, but only 25 (4%) were finally diagnosed with confirmed ZIKV infection (including two pregnant women, without adverse fetal outcomes), 88% (n:22) presented with fever and 92% (n:23) with rash. 56% (n:14) arthralgia and/or myalgia and 28% (n:7) conjunctivitis. The presence of conjunctivitis, fever and rash were associated with an 8.9 (95% CI: 2.2-34.9), 6.4 (95% CI: 1.2-33.3) and 72.3 (95% CI: 9.2-563.5) times greater probability of confirmed ZIKV infection, respectively.

CONCLUSION

Travel characteristics and clinical presentation may help clinicians to optimize requests for microbiological testing. Diagnosis of arboviriasis in travellers arriving form endemic areas remains a challenge for clinicians, but must be detected for the possible transmission outside endemic areas, where the vector is present.

[Epidemic and emerging prone-infectious diseases: Lessons learned and ways forward]

Africa along side with south-east Asia are the epicentres of emerging and epidemic prone-infectious diseases and megacity biosecurity threat scenarios. Massive mobility and reluctance in the populations exposed to epidemic and emerging prone-infectious diseases coupled by a weak health system made disease alert and control measures difficult to implement. The investigation of virus detection and persistence in semen across a range of emerging viruses is useful for clinical and public health reasons, in particular for viruses that lead to high mortality or morbidity rates or to epidemics. Innovating built facility to safely treat patients with highly pathogenic infectious diseases is urgently need, not only to prevent the spread of infection from patients to healthcare workers but also to offer provision of relatively invasive organ support, whenever considered appropriate, without posing additional risk to staff. Despite multiple challenges, the need to conduct research during epidemics is inevitable, and candidate products must continue undergoing rigorous trials. Preparedness including management of complex humanitarian crises with community distrust is a cornerstone in response to high consequence emerging infectious disease outbreaks and imposes strengthening of the public health response infrastructure and emergency outbreak systems in high-risk regions.

Performance evaluation of the Diasorin LIAISON® XL Zika capture IgM CLIA test

Because Zika virus (ZIKV) can cause serious birth defects and is involved in cases of Guillain-Barré syndrome, the ZIKV outbreak in the American continent in 2015 resulted in an enormous need for ZIKV diagnostic tools. We evaluated the LIAISON® XL Zika Capture IgM test on 106 samples from patients, mainly travelers, with a confirmed or probable ZIKV infection. Sensitivity between 0 and 84 days after onset of symptoms was 92.5%. Specificity was evaluated on a panel of 56 samples known to cause possible cross-reactions. Cross-reaction with DENV antibodies was limited (10.5%) but false-positive results occurred in samples from patients with malaria, CMV and EBV infections.

Zika virus disease in Spain. Surveillance results and epidemiology on reported cases, 2015-2017

INTRODUCTION AND OBJECTIVE

Zika virus disease is a challenge for public health due to its rapid spread and potential foetal complications. Although it is imported in Spain, there is a risk of autochthonous transmission due to Aedes albopictus presence. Zika disease and congenital cases have been under surveillance since 2016. The objective of this study is to explore the epidemiology of disease and pregnancies result.

MATERIAL AND METHODS

A descriptive study was carried out into cases reported to the National Surveillance Network (RENAVE) during the 30/11/2015 to 31/12/2017 period. The case definition and the survey are included in the RENAVE protocol. The variables were: date; notifying region (Autonomous Community (AC)); pregnancy and its evolution; case classification; mode of transmission; country or region of infection; socio-demographical, clinical and microbiological data. A descriptive analysis of the cases and their distribution according to the other variables was carried out.

RESULTS

A total of 512 cases were reported by 17 ACs. 507 were non-congenital, of which 327 (64.5%) were women (52.5% of childbearing age). 403 cases (79.5%) corresponded to 2016 and 193 (38.1%) resided in regions with A. albopictus presence between May and October. 96.1% of imported cases were infected in America (51.7% while visiting relatives). Three cases (3.9%) of congenital Zika virus infection were detected among 77 pregnant women.

CONCLUSIONS

The evolution of reported cases was in accordance with that of the epidemic in America. The largest group of travellers was young women who travelled to Latin America on family visits. Pregnancy monitoring resulted in the identification of Zika related foetal complications.

Zika virus threshold determines transmission by European Aedes albopictus mosquitoes

Since its emergence in Yap Island in 2007, Zika virus (ZIKV) has affected all continents except Europe. Despite the hundreds of cases imported to European countries from ZIKV-infested regions, no local cases have been reported in localities where the ZIKV-competent mosquito Aedes albopictus is well established. Here we analysed the vector competence of European Aedes (aegypti and albopictus) mosquitoes to different genotypes of ZIKV. We demonstrate that Ae. albopictus from France was less susceptible to the Asian ZIKV than to the African ZIKV. Critically we show that effective crossing of anatomical barriers (midgut and salivary glands) after an infectious blood meal depends on a viral load threshold to trigger: (i) viral dissemination from the midgut to infect mosquito internal organs and (ii) viral transmission from the saliva to infect a vertebrate host. A viral load in body ≥4800 viral copies triggered dissemination and ≥12,000 viral copies set out transmission. Only 27.3% and 18.2% of Ae. albopictus Montpellier mosquitoes meet respectively these two criteria. Collectively, these compelling results stress the poor ability of Ae. albopictus to sustain a local transmission of ZIKV in Europe and provide a promising tool to evaluate the risk of ZIKV transmission in future outbreaks.

Islands as Hotspots for Emerging Mosquito-Borne Viruses: A One-Health Perspective

During the past ten years, an increasing number of arbovirus outbreaks have affected tropical islands worldwide. We examined the available literature in peer-reviewed journals, from the second half of the 20th century until 2018, with the aim of gathering an overall picture of the emergence of arboviruses in these islands. In addition, we included information on environmental and social drivers specific to island setting that can facilitate the emergence of outbreaks. Within the context of the One Health approach, our review highlights how the emergence of arboviruses in tropical islands is linked to the complex interplay between their unique ecological settings and to the recent changes in local and global sociodemographic patterns. We also advocate for greater coordination between stakeholders in developing novel prevention and mitigation approaches for an intractable problem.

Widespread circulation of West Nile virus, but not Zika virus in southern Iran

West Nile virus (WNV) and Zika virus (ZIKV) are mosquito-borne viral infections. Over the past few decades, WNV has been associated with several outbreaks involving high numbers of neuroinvasive diseases among humans. The recent re-emergence of ZIKV has been associated with congenital malformation and also with Guillain-Barre syndrome in adults. The geographic range of arthropod-borne viruses has been rapidly increasing in recent years. The objectives of this study were to determine the presence of IgG specific antibodies and the genome of WNV and ZIKV in human samples, as well as WNV and ZIKV genomes in wild-caught mosquitoes in urban and rural areas of the Hormozgan province, in southern Iran. A total of 494 serum samples were tested for the presence of WNV and ZIKV IgG antibodies using ELISA assays. One hundred and two (20.6%) samples were reactive for WNV IgG antibodies. All serum samples were negative for ZIKV IgG antibodies. Using the multivariable logistic analysis, age (45+ vs. 1-25; OR = 3.4, 95% C.I.: 1.8-6.3), occupation (mostly outdoor vs. mostly indoor; OR = 2.4, 95% C.I.: 1.1-5.2), and skin type(type I/II vs. type III/IV and type V/VI; OR = 4.3, 95% C.I.: 1.7-10.8 and OR = 2.7, 95% C.I.: 1.3-5.5 respectively, skin types based on Fitzpatrick scale) showed significant association with WNV seroreactivity. We collected 2,015 mosquitoes in 136 pools belonging to 5 genera and 14 species. Three pools of Culex pipiens complex were positive for WNV RNA using real-time reverse transcription polymerase chain reaction (rtRT-PCR). ZIKV RNA was not detected in any of the pools. All WNV ELISA reactive serum samples were negative for WNV RNA. In conclusion, we provided evidence of the establishment of WNV in southern Iran and no proof of ZIKV in serum samples or in mosquito vectors. The establishment of an organized arbovirus surveillance system and active case finding strategies seems to be necessary.

Zika virus infection in the returning traveller: what every neurologist should know

Zika virus has been associated with a wide range of neurological complications. Neurologists in areas without current active transmission of the virus may be confronted with Zika-associated neurological disease, as a large number of returning travellers with Zika virus infection have been reported and the virus continues to spread to previously unaffected regions. This review provides an overview of Zika virus-associated neurological disease and aims to support neurologists who may encounter patients returning from endemic areas.

Sexual transmission of Zika virus and other flaviviruses: A living systematic review

BACKGROUND

Health authorities in the United States and Europe reported an increasing number of travel-associated episodes of sexual transmission of Zika virus (ZIKV) following the 2015-2017 ZIKV outbreak. This, and other scientific evidence, suggests that ZIKV is sexually transmissible in addition to having its primary mosquito-borne route. The objective of this systematic review and evidence synthesis was to clarify the epidemiology of sexually transmitted ZIKV.

METHODS AND FINDINGS

We performed a living (i.e., continually updated) systematic review of evidence published up to 15 April 2018 about sexual transmission of ZIKV and other arthropod-borne flaviviruses in humans and other animals. We defined 7 key elements of ZIKV sexual transmission for which we extracted data: (1) rectal and vaginal susceptibility to infection, (2) incubation period following sexual transmission, (3) serial interval between the onset of symptoms in a primary and secondary infected individuals, (4) duration of infectiousness, (5) reproduction number, (6) probability of transmission per sex act, and (7) transmission rate. We identified 1,227 unique publications and included 128, of which 77 presented data on humans and 51 presented data on animals. Laboratory experiments confirm that rectal and vaginal mucosae are susceptible to infection with ZIKV and that the testis serves as a reservoir for the virus in animal models. Sexual transmission was reported in 36 human couples: 34/36 of these involved male-to-female sexual transmission. The median serial symptom onset interval in 15 couples was 12 days (interquartile range: 10-14.5); the maximum was 44 days. We found evidence from 2 prospective cohorts that ZIKV RNA is present in human semen with a median duration of 34 days (95% CI: 28-41 days) and 35 days (no CI given) (low certainty of evidence, according to GRADE). Aggregated data about detection of ZIKV RNA from 37 case reports and case series indicate a median duration of detection of ZIKV of 40 days (95% CI: 30-49 days) and maximum duration of 370 days in semen. In human vaginal fluid, median duration was 14 days (95% CI: 7-20 days) and maximum duration was 37 days (very low certainty). Infectious virus in human semen was detected for a median duration of 12 days (95% CI: 1-21 days) and maximum of 69 days. Modelling studies indicate that the reproduction number is below 1 (very low certainty). Evidence was lacking to estimate the incubation period or the transmission rate. Evidence on sexual transmission of other flaviviruses was scarce. The certainty of the evidence is limited because of uncontrolled residual bias.

CONCLUSIONS

The living systematic review and sexual transmission framework allowed us to assess evidence about the risk of sexual transmission of ZIKV. ZIKV is more likely transmitted from men to women than from women to men. For other flaviviruses, evidence of sexual transmissibility is still absent. Taking into account all available data about the duration of detection of ZIKV in culture and from the serial interval, our findings suggest that the infectious period for sexual transmission of ZIKV is shorter than estimates from the earliest post-outbreak studies, which were based on reverse transcription PCR alone.

Zika virus: Where to from here?

After the waves of reported cases of infection with Zika virus swept across the Americas in 2015-16, the overall transmission of the virus in the Western Hemisphere declined in 2017. Between June 8 and August 31, 2017, only 16 new cases of Zika virus infection, all travel-related, were reported in Canada. This represents an 88% reduction in the cases recorded during the same time frame in 2016. Herd immunity undoubtedly constrains the transmission of the virus in endemic regions. However, while most countries in the Americas are no longer observing continuous transmission in the form of sustained increases over time, some areas are experiencing a notable resurgence. Zika virus, in the wake of dengue, West Nile and chikungunya, has become one of the globalized emerging infections-proliferating beyond previously restricted geographic zones. Zika virus is no longer deemed a global health crisis but the virus' unique potential to cause neurological anomalies in fetuses remains a significant concern.