Prevalence and Incidence of Zika Virus Infection Among Household Contacts of Patients With Zika Virus Disease, Puerto Rico, 2016-2017

Estimating transmissibility of Zika virus in Colombia in the presence of surveillance bias

The 2015-2016 Zika virus outbreak in the Americas presented significant challenges in understanding the transmission dynamics due to substantial reporting biases, as women of reproductive age (15-39 years) were disproportionately represented in the surveillance data when public awareness of relationship between Zika and microcephaly increased. Using national surveillance data from Colombia during July 27, 2015-November 21, 2016, we developed a Bayesian hierarchical modeling framework to reconstruct the true numbers of symptomatic cases and estimate transmission parameters while accounting for differential reporting across age-sex groups. Our model revealed that the detection rate of symptomatic cases among women of reproductive age was 99% (95% CI: 98.7-100), compared to 85.4% (95% CI: 84.7-86.1) in other demographic groups. After correcting for these biases, our results showed that females aged 15-39 years remained 82.8% (95% CI: 80.2-85.2%) more susceptible to Zika symptomatic infection than males of the same age, independent of differential reporting areas. Departments with medium-high altitude, medium-high population density, low coverage of forest, or high dengue incidence from 2011-2015 exhibited greater Zika risk. This study underscores the importance of accounting for surveillance biases in epidemiological studies to better understand factors influencing Zika transmission and to inform disease control and prevention.

Effect of Sexual Partnerships on Zika Virus Transmission in Virus-Endemic Region, Northeast Brazil

The epidemiologic effects of Zika virus (ZIKV) sexual transmission in virus-endemic countries remain unclear. We conducted a 2-level, linear mixed-effects logistic regression analysis by using a recently acquired population-based ZIKV and chikungunya virus (CHIKV) serologic dataset obtained from persons residing in Northeast Brazil (n = 2,070 participants). We adjusted mathematical models for housing type and age of participants; the models indicated a significantly higher likelihood of ZIKV seropositivity among persons engaged in a sexual relationship within the same household (odds ratio 1.25 [95% CI 1.00-1.55]; p = 0.047), regardless of their partner's ZIKV serostatus, and among participants with a ZIKV-seropositive sex partner within the same household (odds ratio 1.54 [95% CI 1.18-2.01]; p = 0.002). CHIKV was also modeled as a control; no sex-associated effects were observed for CHIKV serology. Inclusion of ZIKV sexual transmission in prevention and control strategies is urgently needed, particularly in ZIKV-endemic regions.

A conformational selection mechanism of flavivirus NS5 for species-specific STAT2 inhibition

Flaviviruses, including Zika virus (ZIKV) and Dengue virus (DENV), rely on their non-structural protein 5 (NS5) for both replication of viral genome and suppression of host IFN signaling. DENV and ZIKV NS5s were shown to facilitate proteosome-mediated protein degradation of human STAT2 (hSTAT2). However, how flavivirus NS5s have evolved for species-specific IFN-suppression remains unclear. Here we report structure-function characterization of the DENV serotype 2 (DENV2) NS5-hSTAT2 complex. The MTase and RdRP domains of DENV2 NS5 form an extended conformation to interact with the coiled-coil and N-terminal domains of hSTAT2, thereby promoting hSTAT2 degradation in cells. Disruption of the extended conformation of DENV2/ZIKV NS5, but not the alternative compact state, impaired their hSTAT2 binding. Our comparative structural analysis of flavivirus NS5s further reveals a conserved protein-interaction platform with subtle amino-acid variations likely underpinning diverse IFN-suppression mechanisms. Together, this study uncovers a conformational selection mechanism underlying species-specific hSTAT2 inhibition by flavivirus NS5.

The seroepidemiology of dengue in a US military population based in Puerto Rico during the early phase of the Zika pandemic

Understanding the burden and risk factors of dengue virus (DENV) infection in Puerto Rico is important for the prevention of dengue in local, traveler and military populations. Using sera from the Department of Defense Serum Repository, we estimated the prevalence and predictors of DENV seropositivity in those who had served in Puerto Rico, stratified by birth or prior residence (“birth/residence”) in dengue-endemic versus non-endemic regions. We selected sera collected in early 2015 from 500 U.S. military members, a time-point also permitting detection of early cryptic Zika virus (ZIKV) circulation. 87.2% were born or resided in a DENV-endemic area before their military service in Puerto Rico. A high-throughput, flow-cytometry-based neutralization assay was employed to screen sera for ZIKV and DENV neutralizing antibodies, and confirmatory testing was done by plaque-reduction neutralization test (PRNT). We identified one Puerto Rico resident who seroconverted to ZIKV by June 2015, suggesting cryptic ZIKV circulation in Puerto Rico at least 4 months before the first reported cases. A further six PRNT-positive presumptive ZIKV infections which were resolved as DENV infections only by the use of paired sera. We noted 66.8% of the total study sample was DENV seropositive by early 2015. Logistic regression analysis indicated that birth/residence in a dengue non-endemic region (before military service in Puerto Rico) was associated with a lower odds of DENV exposure by January—June 2015 (aOR = 0.28, p = 0.001). Among those with birth/residence in a non-endemic country, we noted moderate evidence to support increase in odds of DENV exposure for each year of military service in Puerto Rico (aOR = 1.58, p = 0.06), but no association with age. In those with birth/residence in dengue-endemic regions (before military service in Puerto Rico), we noted that age (aOR = 1.04, p = 0.02), rather than duration of Puerto Rico service, was associated with dengue seropositivity, suggesting earlier lifetime DENV exposure. Our findings provide insights into the burden and predictors of DENV infection in local, traveler and military populations in Puerto Rico. Our study also highlights substantial PRNT ZIKV false-positivity when paired sera are not available, even during periods of very low ZIKV prevalence.

Viral genome-based Zika virus transmission dynamics in a paediatric cohort during the 2016 Nicaragua epidemic

BACKGROUND

Nicaragua experienced a large Zika epidemic in 2016, with up to 50% of the population in Managua infected. With the domesticated Aedes aegypti mosquito as its vector, it is widely assumed that Zika virus transmission occurs within the household and/or via human mobility. We investigated these assumptions by using viral genomes to trace Zika transmission spatially.

METHODS

We analysed serum samples from 119 paediatric Zika cases participating in the long-standing Paediatric Dengue Cohort Study in Managua, which was expanded to include Zika in 2015. An optimal spanning directed tree was constructed by minimizing the differences in viral sequence diversity composition between patient nodes, where low-frequency variants were used to increase the resolution of the inferred Zika outbreak dynamics.

FINDINGS

Out of the 18 houses where pairwise difference in sample collection dates among all the household members was within 30 days, we only found two where viruses from individuals within the same household were up to 10th-most closely linked to each other genetically. We also identified a substantial number of transmission events involving long geographical distances (n=30), as well as potential super-spreading events in the estimated transmission tree.

INTERPRETATION

Our finding highlights that community transmission, often involving long geographical distances, played a much more important role in epidemic spread than within-household transmission.

FUNDING

This study was supported by an NUS startup grant (OMS) and grants R01 AI099631 (AB), P01 AI106695 (EH), P01 AI106695-03S1 (FB), and U19 AI118610 (EH) from the US National Institutes of Health.

Different epidemiological profiles in patients with Zika and dengue infection in Tapachula, Chiapas in Mexico (2016-2018): an observational, prospective cohort study

BACKGROUND

The introduction of Zika and chikungunya to dengue hyperendemic regions increased interest in better understanding characteristics of these infections. We conducted a cohort study in Mexico to evaluate the natural history of Zika infection. We describe here the frequency of Zika, chikungunya and dengue virus infections immediately after Zika introduction in Mexico, and baseline characteristics of participants for each type of infection.

METHODS

Prospective, observational cohort evaluating the natural history of Zika virus infection in the Mexico-Guatemala border area. Patients with fever, rash or both, meeting the modified criteria of PAHO for probable Zika cases were enrolled (June 2016-July 2018) and followed-up for 6 months. We collected data on sociodemographic, environmental exposure, clinical and laboratory characteristics. Diagnosis was established based on viral RNA identification in serum and urine samples using RT-PCR for Zika, chikungunya, and dengue. We describe the baseline sociodemographic and environmental exposure characteristics of participants according to diagnosis, and the frequency of these infections over a two-year period immediately after Zika introduction in Mexico.

RESULTS

We enrolled 427 participants. Most patients (n = 307, 65.7%) had an acute illness episode with no identified pathogen (UIE), 37 (8%) Zika, 82 (17.6%) dengue, and 1 (0.2%) chikungunya. In 2016 Zika predominated, declined in 2017 and disappeared in 2018; while dengue increased after 2017. Patients with dengue were more likely to be men, younger, and with lower education than those with Zika and UIE. They also reported closer contact with water sources, and with other people diagnosed with dengue. Participants with Zika reported sexual exposure more frequently than people with dengue and UIE. Zika was more likely to be identified in urine while dengue was more likely found in blood in the first seven days of symptoms; but PCR results for both were similar at day 7-14 after symptom onset.

CONCLUSIONS

During the first 2 years of Zika introduction to this dengue hyper-endemic region, frequency of Zika peaked and fell over a two-year period; while dengue progressively increased with a predominance in 2018. Different epidemiologic patterns between Zika, dengue and UIE were observed. Trial registration Clinical.Trials.gov (NCT02831699).

Early Embryonic Loss Following Intravaginal Zika Virus Challenge in Rhesus Macaques

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) and is primarily transmitted by Aedes species mosquitoes; however, ZIKV can also be sexually transmitted. During the initial epidemic and in places where ZIKV is now considered endemic, it is difficult to disentangle the risks and contributions of sexual versus vector-borne transmission to adverse pregnancy outcomes. To examine the potential impact of sexual transmission of ZIKV on pregnancy outcome, we challenged three rhesus macaques (Macaca mulatta) three times intravaginally with 1 x 107 PFU of a low passage, African lineage ZIKV isolate (ZIKV-DAK) in the first trimester (~30 days gestational age). Samples were collected from all animals initially on days 3 through 10 post challenge, followed by twice, and then once weekly sample collection; ultrasound examinations were performed every 3-4 days then weekly as pregnancies progressed. All three dams had ZIKV RNA detectable in plasma on day 3 post-ZIKV challenge. At approximately 45 days gestation (17-18 days post-challenge), two of the three dams were found with nonviable embryos by ultrasound. Viral RNA was detected in recovered tissues and at the maternal-fetal interface (MFI) in both cases. The remaining viable pregnancy proceeded to near term (~155 days gestational age) and ZIKV RNA was detected at the MFI but not in fetal tissues. These results suggest that sexual transmission of ZIKV may represent an underappreciated risk of pregnancy loss during early gestation.

An evaluation of Bacillus thuringiensis israelensis (AM65-52) treatment for the control of Aedes aegypti using vehicle-mounted WALS® application in a densely populated urban area of Puerto Rico

BACKGROUND

With a shortage of effective options for control of Aedes aegypti in Puerto Rico due to widespread resistance to conventional mosquito adulticides, an alternative approach was investigated to reduce vector populations. In two areas (totaling 144 ha) of the municipality of Bayamón, Puerto Rico, Bacillus thuringiensis israelensis (Bti) AM65-52 WDG was applied at a rate of 500 g/ha using vehicle-mounted aqueous wide-area larvicide spray applications weekly for 4 weeks and then every other week for a further 16 weeks. Bioassay jars were placed in the field to monitor for deposition of Bti droplets in open spaces, and under vegetation and building coverage. Autocidal gravid ovitraps were placed throughout the field site to monitor the population of adult female Ae. aegypti in both treatment and control sites.

RESULTS

Larvicide spray was successfully deposited into jars in an array of open and covered locations, as confirmed by larval bioassays. After the fourth weekly spraying, differences in autocidal gravid ovitrap densities were observed between treatment and control sites resulting in 62% (P = 0.0001) and 28% (P < 0.0001) reductions in adult female Ae. aegypti numbers.

CONCLUSION

Repeated wide-area larvicide spray application of Bti AM65-52 WDG to residential areas in Puerto Rico effectively suppressed dengue vector populations. The success of this trial has led to expansion of the WALS® program to a larger area of Bayamón and other municipalities in Puerto Rico. © 2020 Society of Chemical Industry.

Estimating incidence of infection from diverse data sources: Zika virus in Puerto Rico, 2016

Emerging epidemics are challenging to track. Only a subset of cases is recognized and reported, as seen with the Zika virus (ZIKV) epidemic where large proportions of infection were asymptomatic. However, multiple imperfect indicators of infection provide an opportunity to estimate the underlying incidence of infection. We developed a modeling approach that integrates a generic Time-series Susceptible-Infected-Recovered epidemic model with assumptions about reporting biases in a Bayesian framework and applied it to the 2016 Zika epidemic in Puerto Rico using three indicators: suspected arboviral cases, suspected Zika-associated Guillain-Barré Syndrome cases, and blood bank data. Using this combination of surveillance data, we estimated the peak of the epidemic occurred during the week of August 15, 2016 (the 33^rd week of year), and 120 to 140 (50% credible interval [CrI], 95% CrI: 97 to 170) weekly infections per 10,000 population occurred at the peak. By the end of 2016, we estimated that approximately 890,000 (95% CrI: 660,000 to 1,100,000) individuals were infected in 2016 (26%, 95% CrI: 19% to 33%, of the population infected). Utilizing multiple indicators offers the opportunity for real-time and retrospective situational awareness to support epidemic preparedness and response.

Zika virus (ZIKV) infections, like many infections, are generally underreported due to asymptomatic, mild, or unrecognized cases. Using available surveillance indicators reflecting imperfect proxies of infection, we developed a modeling approach to estimate the weekly incidence of infection by combining independent surveillance indicators and assumptions about system-specific reporting biases in a Bayesian framework. Using our approach, we estimated that approximately 890,000 people in the population were infected with Zika in Puerto Rico in 2016, much higher than the 36,316 reported confirmed infections. Our framework has broad application to other diseases where cases may be underreported through traditional disease surveillance and can provide near real-time changes in incidences.

COVID-19 Testing, Epidemic Features, Hospital Outcomes, and Household Prevalence, New York State-March 2020

Background

The United States’ COVID-19 epidemic has grown extensively since February 2020, with substantial associated hospitalizations and mortality; New York State (NYS) has emerged as the national epicenter. We report on the extent of testing and test results during the month of March in NYS, along with risk factors, outcomes, and household prevalence among initial cases subject to in-depth investigations.

Methods

Specimen collection for COVID-19 testing was conducted in healthcare settings, community-based collection sites, and by home testing teams. Information on demographics, risk factors, and hospital outcomes of cases was obtained through epidemiological investigations and an electronic medical records match, and summarized descriptively. Active testing of initial case’s households enabled estimation of household prevalence.

Results

During March In NYS, outside of New York City, a total of 47,326 persons tested positive for SARS-CoV-2, out of 141,495 tests (33% test-positive), with the highest number of cases located in the metropolitan region counties. Among 229 initial cases diagnosed through March 12, by March 30 13% were hospitalized and 2% died. Testing conducted among 498 members of these case’s households found prevalent infection among 57%; excluding first-reported cases 38%. In these homes, we found a significant age gradient in prevalence, from 23% among those <5 years to 68% among those ≥65 years (p<.0001).

Conclusions

New York State faced a substantial and increasing COVID-19 outbreak during March 2020. The earliest cases had high levels of infection in their households and by the end of the month, the risks of hospitalization and death were high.

Epidemiologic and spatiotemporal trends of Zika Virus disease during the 2016 epidemic in Puerto Rico

Background

After Zika virus (ZIKV) emerged in the Americas, laboratory-based surveillance for arboviral diseases in Puerto Rico was adapted to include ZIKV disease.

Methods and findings

Suspected cases of arboviral disease reported to Puerto Rico Department of Health were tested for evidence of infection with Zika, dengue, and chikungunya viruses by RT-PCR and IgM ELISA. To describe spatiotemporal trends among confirmed ZIKV disease cases, we analyzed the relationship between municipality-level socio-demographic, climatic, and spatial factors, and both time to detection of the first ZIKV disease case and the midpoint of the outbreak. During November 2015–December 2016, a total of 71,618 suspected arboviral disease cases were reported, of which 39,717 (55.5%; 1.1 cases per 100 residents) tested positive for ZIKV infection. The epidemic peaked in August 2016, when 71.5% of arboviral disease cases reported weekly tested positive for ZIKV infection. Incidence of ZIKV disease was highest among 20–29-year-olds (1.6 cases per 100 residents), and most (62.3%) cases were female. The most frequently reported symptoms were rash (83.0%), headache (64.6%), and myalgia (63.3%). Few patients were hospitalized (1.2%), and 13 (<0.1%) died. Early detection of ZIKV disease cases was associated with increased population size (log hazard ratio [HR]: -0.22 [95% confidence interval -0.29, -0.14]), eastern longitude (log HR: -1.04 [-1.17, -0.91]), and proximity to a city (spline estimated degrees of freedom [edf] = 2.0). Earlier midpoints of the outbreak were associated with northern latitude (log HR: -0.30 [-0.32, -0.29]), eastern longitude (spline edf = 6.5), and higher mean monthly temperature (log HR: -0.04 [-0.05, -0.03]). Higher incidence of ZIKV disease was associated with lower mean precipitation, but not socioeconomic factors.

Conclusions

During the ZIKV epidemic in Puerto Rico, 1% of residents were reported to public health authorities and had laboratory evidence of ZIKV disease. Transmission was first detected in urban areas of eastern Puerto Rico, where transmission also peaked earlier. These trends suggest that ZIKV was first introduced to Puerto Rico in the east before disseminating throughout the island.

During epidemics of Zika virus disease in the Americas in 2015 and 2016, assessment of transmission dynamics was limited by inconsistent laboratory testing of patients with suspected Zika virus disease. This limitation was further complicated by co-circulation of dengue and chikungunya viruses, which cause illnesses clinically similar to Zika virus disease. In Puerto Rico, all reported suspect cases of arboviral disease were tested for Zika, dengue, and chikungunya virus infection throughout the epidemic, which allowed for fine-scale analysis of epidemiologic and spatiotemporal trends. In total, 39,717 cases of Zika virus disease were detected, or roughly 1% of all residents of Puerto Rico. Young adults and females were most affected. Disease was mostly mild, as only 1% of cases were hospitalized. Thirteen patients with Zika virus disease died, most of whom had Guillain-Barré syndrome or severe underlying illnesses. Early detection of Zika virus disease cases was associated with more populated areas of eastern Puerto Rico, where early detection of peak case numbers also occurred, particularly in warmer areas. These trends suggest that, in contrast to prior epidemics of dengue and chikungunya that started in the San Juan metropolitan region, the Zika virus epidemic appears to have begun in eastern Puerto Rico.

Follow-Up Household Serosurvey in Northeast Brazil for Zika Virus: Sexual Contacts of Index Patients Have the Highest Risk for Seropositivity

BACKGROUND

Zika virus (ZIKV) is a mosquito-borne virus that is also transmitted sexually; however, the epidemiological relevance of ZIKV sexual transmission in endemic regions is unclear.

METHODS

We performed a household-based serosurvey in Northeast Brazil to evaluate the differential exposure to ZIKV and chikungunya virus (CHIKV) among households. Individuals who participated in our previous arboviral disease cohort (indexes) were recontacted and enrolled, and their household members were newly enrolled.

RESULTS

The relative risk of sexual partners being ZIKV-seropositive when living with a ZIKV-seropositive index participant was significantly higher, whereas this was not observed among nonsexual partners of the index. For CHIKV, both sexual and nonsexual partner household members living with a CHIKV-seropositive index had a significantly higher risk of being seropositive. In the nonindex-based dyadic and generalized linear mixed model analyses, the odds of sexual dyads having a concordant ZIKV plaque reduction neutralization test result was significantly higher. We have also analyzed retrospective clinical data according to the participants' exposure to ZIKV and CHIKV.

CONCLUSIONS

Our data suggest that ZIKV sexual transmission may be a key factor for the high ZIKV seroprevalence among households in endemic areas and raises important questions about differential disease from the 2 modes of transmission.

Sexual Transmission of Arboviruses: A Systematic Review

Arthropod-borne viruses (arboviruses) are primarily maintained in nature in transmission cycles between hematophagous arthropods and vertebrate hosts, but an increasing number of arboviruses have been isolated from or indirectly detected in the urogenital tract and sexual secretions of their vertebrate hosts, indicating that further investigation on the possibility of sexual transmission of these viruses is warranted. The most widely recognized sexually-transmitted arbovirus is Zika virus but other arboviruses, including Crimean-Congo hemorrhagic fever virus and dengue virus, might also be transmitted, albeit occasionally, by this route. This review summarizes our current understanding on the ability of arboviruses to be sexually transmitted. We discuss the sexual transmission of arboviruses between humans and between vertebrate animals, but not arthropod vectors. Every taxonomic group known to contain arboviruses (Asfarviridae, Bunyavirales, Flaviviridae, Orthomyxoviridae, Reoviridae, Rhabdoviridae and Togaviridae) is covered.

The Endless Challenges of Arboviral Diseases in Brazil

In this Editorial, we list and discuss some of the main challenges faced by the population and public health authorities in Brazil concerning arbovirus infections, including the occurrence of concurrent epidemics like the ongoing SARS-CoV-2/COVID-19 pandemic.

From Ancient to Emerging Infections: The Odyssey of Viruses in the Male Genital Tract

The male genital tract (MGT) is the target of a number of viral infections that can have deleterious consequences at the individual, offspring, and population levels. These consequences include infertility, cancers of male organs, transmission to the embryo/fetal development abnormalities, and sexual dissemination of major viral pathogens such as human immunodeficiency virus (HIV) and hepatitis B virus. Lately, two emerging viruses, Zika and Ebola, have additionally revealed that the human MGT can constitute a reservoir for viruses cleared from peripheral circulation by the immune system, leading to their sexual transmission by cured men. This represents a concern for future epidemics and further underlines the need for a better understanding of the interplay between viruses and the MGT. We review here how viruses, from ancient viruses that integrated the germline during evolution through old viruses (e.g., papillomaviruses originating from Neanderthals) and more modern sexually transmitted infections (e.g., simian zoonotic HIV) to emerging viruses (e.g., Ebola and Zika) take advantage of genital tract colonization for horizontal dissemination, viral persistence, vertical transmission, and endogenization. The MGT immune responses to viruses and the impact of these infections are discussed. We summarize the latest data regarding the sources of viruses in semen and the complex role of this body fluid in sexual transmission. Finally, we introduce key animal findings that are relevant for our understanding of viral infection and persistence in the human MGT and suggest future research directions.

Evidence-Based Process for Prioritizing Positive Behaviors for Promotion: Zika Prevention in Latin America and the Caribbean and Applicability to Future Health Emergency Responses

To maximize the impact of Zika prevention programming efforts, a prioritization process for social and behavior change programming was developed based on a combination of research evidence and programmatic experience. Prioritized behaviors were: application of mosquito repellent, use of condoms, removing unintentional standing water, covering and scrubbing walls of water storage containers, seeking prenatal care, and seeking counseling on family planning if not planning to get pregnant.

Since the 2015 Zika outbreak in Latin America and the Caribbean, a plethora of behavior change messages have been promoted to reduce Zika transmission. One year after the United States Agency for International Development (USAID) initiated its Zika response, more than 30 variants of preventive behaviors were being promoted. This situation challenged social and behavior change (SBC) programming efforts that require a coordinated response and agreed upon set of focus behaviors to be effective. To support USAID implementing partners in harmonizing prevention efforts to reduce Zika infection, we developed an evidence-based process to identify behaviors with the highest potential to reduce Zika infection and transmission. We compiled a full list of behaviors and selected the most promising for a full evidence review. The review included systematic keyword searches on Google Scholar, extraction of all relevant published articles on Aedes-borne diseases between 2012 and 2018, review of seminal papers, and review of gray literature. We examined articles to determine each behavior's potential effectiveness in preventing Zika transmission or reducing the Aedes aegypti population. We also developed assessment criteria to delineate the ease with which the target population could adopt each behavior, including: (1) required frequency; (2) feasibility of the behavior; and (3) accessibility and cost of the necessary materials in the setting. These behaviors were refined through a consensus-building process with USAID's Zika implementing partners, considering contextual factors. The resulting 7 evidence-based preventive behaviors have high potential to strengthen SBC programming's impact in USAID's Zika response: (1) apply mosquito repellent, (2) use condoms during pregnancy, (3) remove standing water, (4) cover water storage containers, (5) clean/remove mosquito eggs from water containers, (6) seek antenatal care, and (7) seek family planning counseling. This case study documents a flexible process that can be adapted to inform the prioritization of behaviors when there is limited evidence available, as during many emergency responses.