Determinants of Heterogeneous Blood Feeding Patterns by Aedes aegypti in Iquitos, Peru

Liebman, Kelly A.; Stoddard, Steven T.; Reiner, Robert C.; Perkins, T. Alex; Astete, Helvio; Sihuincha, Moisés; Halsey, Eric S.; Kochel, Tadeusz J.; Morrison, Amy C.; Scott, Thomas W.

doi:10.1371/journal.pntd.0002702

Cited by 69 publications

(76 citation statements)

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“…Another limiting assumption of the SIR model is that of homogeneous encounters between people and mosquitoes 44 , which are understood to be extensive for mosquito-borne diseases 22 . Mathematical analyses 21 in this case show that a seemingly infinite complexity of relationships between R 0 and final epidemic size are possible in a heterogeneous system.…”

Section: Methodsmentioning

confidence: 99%

“…Although there is no theoretical justification for this or any other particular scaling relationship, it is consistent with theoretical expectations 21 that attack rates should be lower in populations with equal R 0 values but more heterogeneous contact patterns, which are typical for transmission by Ae. aegypti 22 . To provide a point of reference for our model-based approach, we also fitted a statistical description of the 13 seroprevalence estimates as a function of the environmental drivers that we considered.…”

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Model-based projections of Zika virus infections in childbearing women in the Americas

et al. 2016

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Zika virus is a mosquito-borne pathogen that is rapidly spreading across the Americas. Due to associations between Zika virus infection and a range of fetal maladies 1,2 , the epidemic trajectory of this viral infection poses a significant concern for the nearly 15 million children born in the Americas each year. Ascertaining the portion of this population that is truly at risk is an important priority. One recent estimate 3 suggested that 5.42 million childbearing women live in areas of the Americas that are suitable for Zika occurrence. To improve on that estimate, which did not take into account the protective effects of herd immunity, we developed a new approach that combines classic results from epidemiological theory with seroprevalence data and highly spatially resolved data about drivers of transmission to make location-specific projections of epidemic attack rates. Our results suggest that 1.65 (1.45-2.06) million childbearing women and 93.4 (81.6-117.1) million people in total could become infected before the first wave of the epidemic concludes. Based on current estimates of rates of adverse fetal outcomes among infected women 2,4,5 , these results suggest that tens of thousands of pregnancies could be negatively impacted by the first wave of the epidemic. These projections constitute a revised upper limit of populations at risk in the current Zika epidemic, and our approach offers a new way to make rapid assessments of the threat posed by emerging infectious diseases more generally.On 1 February 2016, the World Health Organization (WHO) designated the ongoing Zika virus epidemic in the Americas as a Public Health Emergency of International Concern (PHEIC), defined as an 'extraordinary event' that 'potentially require[s] a coordinated international response' 6 . This declaration acknowledges the high potential for Zika to establish across the Americas given that its dominant vector, the Aedes aegypti mosquito, is endophilic and occupies an exceptionally broad geographical range 7 . Concern underlying this rare WHO declaration also stems from an association between Zika virus infection in pregnant women and a range of adverse fetal outcomes 2 , most notably congenital microcephaly 1 . As of 30 June 2016, there were 1,674 confirmed cases of microcephaly associated with Zika virus infection in five countries 8 , and there is widespread concern that these numbers could increase further as the virus continues to spread across the Americas 9 .A number of uncertainties surround the future of the Zika epidemic in the Americas, particularly questions about how many women may be at risk of having children with congenital microcephaly and other adverse outcomes associated with Zika virus infection 10 . Of women who become infected with Zika virus during a vulnerable stage of their pregnancy, evidence is emerging that 1-13% may go on to develop congenital microcephaly 2,4,5 .However, the number of women who become infected with Zika virus during that timeframe is difficult to ascertain. One recent study 3 estimat...

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Section: Methodsmentioning

confidence: 99%

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Model-based projections of Zika virus infections in childbearing women in the Americas

et al. 2016

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“…Quantitative estimates of the relative contribution to DENV transmission among disease categories remain to be determined by combining assessments of magnitude and duration of infectiousness across the infectious period of different people with measures of various people's exposure to biting mosquitoes during the course of their infection (23). Larger sample sizes than in the present study and sequential mosquito feedings on the same person will help to further clarify the role of presymptomatic and asymptomatic infections in DENV transmission.…”

Section: Discussionmentioning

confidence: 93%

Asymptomatic humans transmit dengue virus to mosquitoes

Duong

Lambrechts

Rácz

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Three-quarters of the estimated 390 million dengue virus (DENV) infections each year are clinically inapparent. People with inapparent dengue virus infections are generally considered dead-end hosts for transmission because they do not reach sufficiently high viremia levels to infect mosquitoes. Here, we show that, despite their lower average level of viremia, asymptomatic people can be infectious to mosquitoes. Moreover, at a given level of viremia, DENV-infected people with no detectable symptoms or before the onset of symptoms are significantly more infectious to mosquitoes than people with symptomatic infections. Because DENV viremic people without clinical symptoms may be exposed to more mosquitoes through their undisrupted daily routines than sick people and represent the bulk of DENV infections, our data indicate that they have the potential to contribute significantly more to virus transmission to mosquitoes than previously recognized.mosquito experimental infection | Cambodia | Aedes aegypti | human-to-mosquito transmission | dengue W ith 3.97 billion people living in 128 countries currently at risk for infection, dengue viruses (DENV-1 to -4) cause more human morbidity and mortality worldwide than any other arthropod-borne virus (1, 2). Aedes aegypti mosquitoes are the primary vectors of DENV throughout the tropics (3). Dengue prevention relies on the control of Ae. aegypti populations, which is failing in most parts of the world due to lack of resources, lack of political will, and/or ineffective implementation (4).Virus transmission from infected humans to mosquitoes is a critical step in dengue epidemiology, but due to logistical constraints it has been directly examined only in a handful of studies to date (5). In initial experimental infections of human volunteers during the 1920s (6, 7), the onset of clinical symptoms occurred 4-9 d after virus inoculation by mosquito bite (8). DENV-infected humans were infectious to mosquitoes from 2 d before to 2 d after the onset of symptoms, and Ae. aegypti fed on viremic people were able to transmit virus to another person after at least 11 d of extrinsic incubation (8). Results from later studies indicated that, for naturally infected people with clinically apparent dengue, the duration of detectable viremia was on average 4-5 d after the onset of symptoms, but could range from 2 to 12 d (9, 10). Investigators in Vietnam fed Ae. aegypti directly on 208 symptomatic, hospitalized dengue patients and reported that the probability of successful human-to-mosquito DENV transmission was coincident with the kinetics of viremia (11). Dengue patients were infectious up to 5 d after the onset of symptoms, which generally corresponded with "defervescence" (11).All previous studies on human-to-mosquito DENV transmission were limited to people with overt illness and did not consider subclinical infections. An estimated 300 million of the total 390 million DENV infections per year are clinically inapparent or mildly symptomatic, i.e., no illness that disrupted a person's ...

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“…Infected humans acquire life-long immunity to the infecting serotype and temporary immunity to other serotypes to which they have not been previously exposed. Several model features are parameterized based on extensive data collection from Iquitos, Peru, including fine-scale patterns of human mobility [24], the demographic composition of households [25], and the geographic 6 arrangement of residential, commercial, and other buildings [26]. Other model features were less well known a priori: the rate at which DENV was seeded into the population, the probability of an infectious mosquito infecting a susceptible human during blood-feeding, and the emergence rate of adult female mosquitoes.…”

Section: Model Descriptionmentioning

confidence: 99%

Model-based assessment of public health impact and cost-effectiveness of dengue vaccination following screening for prior exposure

España

Yao

Anderson

et al. 2018

Preprint

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The tetravalent dengue vaccine CYD-TDV (Dengvaxia®) is the first licensed vaccine against dengue, but recent findings indicate an elevated risk of severe disease among vaccinees without prior dengue virus (DENV) exposure. The World Health Organization currently recommends CYD-TDV only for individuals with serological confirmation of past DENV exposure. Our objective was to evaluate the potential impact and cost-effectiveness of vaccination following serological screening. We used an agent-based model to simulate DENV transmission over a 30-year timeframe, with and without vaccination. We considered a range of values for the proportion of vaccinees with prior DENV exposure. We projected the proportion of symptomatic and hospitalized cases averted as a function of the sensitivity and specificity of serological screening. We evaluated the cost-effectiveness of screening and vaccination under economic scenarios representative of Brazil and the Philippines. We found that public health impact depended primarily on the sensitivity of serological screening in high-transmission settings and on a combination of sensitivity and specificity in low-transmission settings. Reducing risk from an individual perspective required high specificity, no less than 0.8. Cost-effectiveness could be achievable from the perspective of a public payer provided that screening sensitivity for prior DENV exposure and the value of a disability-adjusted life-year were both high. Costeffectiveness was also achievable from an individual perspective, particularly with high screening specificity and low coverage. Whereas the results of this analysis offer general guidelines about CYD-TDV vaccination, decisions in specific contexts would benefit from additional, more context-specific modeling analyses. Vaccination with CYD-TDV following serological screening could have a positive impact in certain epidemiological settings, provided that screening is highly specific, at least moderately sensitive, and inexpensive.. CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/367060 doi: bioRxiv preprint first posted online Jul. 11, 2018; 2 INTRODUCTION A safe and effective dengue vaccine could have a major public health impact, as dengue causes approximately 9,000 deaths and between 50-100 million clinically apparent cases worldwide every year [1,2], with increasing geographic distribution [3]. The first licensed dengue vaccine, CYD-TDV (Dengvaxia®), is a tetravalent, live-attenuated vaccine that was licensed in multiple countries after demonstrating efficacy against symptomatic disease in phase-III trials [4,5]. Protection has been hypothesized to derive primarily from the vaccine functioning as a "silent infection" [6]. Following their first natural infection subsequent to vaccination, this mechanism would result in vaccinees with prior dengue v...

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Determinants of Heterogeneous Blood Feeding Patterns by Aedes aegypti in Iquitos, Peru

Cited by 69 publications

References 34 publications

Model-based projections of Zika virus infections in childbearing women in the Americas

Model-based projections of Zika virus infections in childbearing women in the Americas

Asymptomatic humans transmit dengue virus to mosquitoes

Model-based assessment of public health impact and cost-effectiveness of dengue vaccination following screening for prior exposure

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