Higher incidence of Zika in adult women than adult men in Rio de Janeiro suggests a significant contribution of sexual transmission from men to women

Coelho, Flávio Codeço; Durovni, Betina; Saraceni, Valéria; Lemos, Cristina; Codeço, Cláudia Torres; Camargo, Sabrina; Carvalho, Luiz Max; Bastos, Leonardo Soares; Arduini, Denise; Villela, Daniel A. M.; Armstrong, Margaret

doi:10.1016/j.ijid.2016.08.023

Cited by 114 publications

(115 citation statements)

References 13 publications

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“…Interestingly, a critical power law-like behavior is nonetheless observed in the heterosexual population at both thresholds. Moreover, our results suggest that the asymmetry in transmission probability is reflected in the asymmetric prevalence within the male and female heterosexual populations, which is reminiscent of recent empirical results (28).…”

Section: Resultssupporting

confidence: 83%

Asymmetric percolation drives a double transition in sexual contact networks

Allard

Althouse

Scarpino

2017

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

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Zika virus (ZIKV) exhibits unique transmission dynamics in that itis concurrently spread by a mosquito vector and through sexual contact. Due to the highly asymmetric durations of infectiousness between males and females-it is estimated that males are infectious for periods up to 10 times longer than females-we show that this sexual component of ZIKV transmission behaves akin to an asymmetric percolation process on the network of sexual contacts. We exactly solve the properties of this asymmetric percolation on random sexual contact networks and show that this process exhibits two epidemic transitions corresponding to a core-periphery structure. This structure is not present in the underlying contact networks, which are not distinguishable from random networks, and emerges because of the asymmetric percolation. We provide an exact analytical description of this double transition and discuss the implications of our results in the context of ZIKV epidemics. Most importantly, our study suggests a bias in our current ZIKV surveillance, because the community most at risk is also one of the least likely to get tested.A bstract modeling of epidemics on networks remains an active field, because some of the most basic features of epidemics are still misunderstood. The classic model is quite simple (1): disease spreads stochastically with a fixed transmission probability, T , through contacts around a given patient zero. The outbreak dies quickly if T is too small but spreads to a macroscopic fraction S of the entire population if T is larger than a threshold Tc. At Tc, most of the typical insights from phase transition theory are valuable. For instance, the sizes of microscopic outbreaks follow a power law distribution, such that the expected size of microscopic outbreaks, s , indicates the position of a phase transition. Indeed, as T increases, s monotonically increases, diverges exactly at Tc, and then monotonically goes down; meanwhile, the expected macroscopic epidemic size, S , starts increasing monotonically at Tc.However, simple modifications to this model can dramatically alter its phenomenology. The epidemic threshold can vanish in networks with a scale-free degree distribution (2) or in growing networks (3). The phase transition can be discontinuous in the case of complex contagions with threshold exposition or reinforcement (4), interacting epidemics (5, 6), or adaptive networks (7-9). Recently, a unique phenomenon of double-phase transitions has also been observed numerically when networks have a very heterogeneous and clustered structure (10, 11).The current Zika virus (ZIKV) epidemic exhibits two unique properties. First, while the main transmission pathway for ZIKV is through a mosquito vector [predominantly Aedes aegypti or Aedes albopictus (13, 14)], a feature which has its own type of well-studied model and behavior (14-16), it can also spread through sexual contacts (17, 18). Second, the probability of sexual transmission is highly asymmetric between males and females. Although this is also true for ot...

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Section: Resultssupporting

confidence: 83%

Asymmetric percolation drives a double transition in sexual contact networks

Allard

Althouse

Scarpino

2017

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

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“…A study analyzing the different incidence of ZIKV in the male and female populations during the 2015 to 2016 outbreak in Brazil noted a significant increase in the incidence of ZIKV infection in females of sexually reproduce age, even after removing bias due to increased surveillance of pregnant women and the observational bias that women are more likely to seek medical help and receive a diagnosis. This data supports the theory that male‐to‐female sexual transmission plays a significant role in ZIKV spread . If the ZIKV is transmitted sexually to an immunologically naïve pregnant woman and the initial site of viral replication is close to or is in fact the uterine wall, is there a higher risk of transplacental infection?…”

Section: Discussionsupporting

confidence: 81%

Congenital Zika syndrome: Pitfalls in the placental barrier

Robinson

Galvan

Trujillo

et al. 2018

Reviews in Medical Virology

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Much progress with respect to congenital Zika virus (ZIKV) pathogenesis has been achieved after the 2015 outbreak in Brazil. It is now accepted that ZIKV is vertically transmitted, infects cells of the developing central nervous system and the placenta, yet it is unclear to what extent placental affection contributes to the development of congenital ZIKV. The association between fulminant villitis and severe fetal involvement emerges as a possibility. ZIKV is unique among the Flaviviruses in its ability to be sexually transmitted, possibly responsible for its teratogenicity. Furthermore, there is controversy over the participation of antibody dependent enhancement (ADE) in patients with non-neutralizing anti-Flavivirus antibodies, a phenomenon previously recognized in serious DENV infections. Our aim was to analyze information regarding the contribution of the placental barrier as an actual player in neonatal ZIKV. Therefore, we underwent a systematic review with keywords "Zika virus" and "ZIKV". Articles were screened for relevance concerning the topics of microcephaly, transplacental transmission, sexual transmission, and ADE. We identified variables that affect the severity of congenital Zika syndrome: age of gestation at maternal infection, the extent of placental disruption (villitis), sexual transmission, initial viral replication at the uterine wall, anti-DENV antibodies, and the possibility of antibody-mediated transcytosis of ZIKV through the placenta. These questions may not seem relevant when Zika becomes endemic, and we are no longer witness to the extreme clinical sequelae seen when the virus moves through an immunologically naïve population; however, characterizing the pathogenesis of congenital Zika syndrome will continue to further our understanding.

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“…The recent success of Zika virus in the Western Hemisphere unequivocally demonstrates the capacity for widespread transmission, yet the combination of lower host viremia levels and mosquito susceptibility suggests that the intensity of vector-to-host transmission could be less efficient than has been observed with previous epidemics of dengue and chikungunya virus infection. It is feasible that efficient sexual transmission could supplement current levels of mosquito transmission ( 38 ) or that vertical transmission among particular mosquito populations could play a larger role than is documented for other flaviviruses ( 39 – 41 ). In addition, as demonstrated here and in previous studies ( 20 ), Zika virus vector competence can vary by virus strain and population, so particular vector/virus combinations may be more efficient at maintaining transmission.…”

Section: Discussionmentioning

confidence: 99%

Effects of Zika Virus Strain andAedesMosquito Species on Vector Competence

Ciota¹,

Bialosuknia²,

Zink³

et al. 2017

Emerg. Infect. Dis.

132

191

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In the Western Hemisphere, Zika virus is thought to be transmitted primarily by Aedes aegypti mosquitoes. To determine the extent to which Ae. albopictus mosquitoes from the United States are capable of transmitting Zika virus and the influence of virus dose, virus strain, and mosquito species on vector competence, we evaluated multiple doses of representative Zika virus strains in Ae. aegypti and Ae. albopictus mosquitoes. Virus preparation (fresh vs. frozen) significantly affected virus infectivity in mosquitoes. We calculated 50% infectious doses to be 6.1–7.5 log10 PFU/mL; minimum infective dose was 4.2 log10 PFU/mL. Ae. albopictus mosquitoes were more susceptible to infection than Ae. aegypti mosquitoes, but transmission efficiency was higher for Ae. aegypti mosquitoes, indicating a transmission barrier in Ae. albopictus mosquitoes. Results suggest that, although Zika virus transmission is relatively inefficient overall and dependent on virus strain and mosquito species, Ae. albopictus mosquitoes could become major vectors in the Americas.

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Higher incidence of Zika in adult women than adult men in Rio de Janeiro suggests a significant contribution of sexual transmission from men to women

Cited by 114 publications

References 13 publications

Asymmetric percolation drives a double transition in sexual contact networks

Asymmetric percolation drives a double transition in sexual contact networks

Congenital Zika syndrome: Pitfalls in the placental barrier

Effects of Zika Virus Strain andAedesMosquito Species on Vector Competence

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