Estimation of reproduction number and probable vector density of the first autochthonous dengue outbreak in Japan in the last 70 years

Furuya, Hiroyuki

doi:10.1007/s12199-015-0488-9

Cited by 9 publications

(5 citation statements)

References 17 publications

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“…Dengue was eliminated in the country by 1945 and transmission has not been observed for 70 years [24]; however, a German traveler visiting Japan in the summer of 2013 was later diagnosed with DENV2 infection upon returning to Germany [25]. In 2014, autochthonous transmission was confirmed in metropolitan Tokyo [26][27][28][29][30][31], resulting in a large outbreak involving a total of 160 confirmed cases, a shockingly high incidence for a previously dengue-free nation. It is now recognized that Japan is indeed at risk of dengue outbreaks during the summer season, indicating that a certain risk exists for the summer Olympic Games in 2020.…”

Section: Introductionmentioning

confidence: 99%

Assessing dengue control in Tokyo, 2014

2019

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Background In summer 2014, an autochthonous outbreak of dengue occurred in Tokyo, Japan, in which Yoyogi Park acted as the focal area of transmission. Recognizing the outbreak, concerted efforts were made to control viral spread, which included mosquito control, public announcement of the outbreak, and a total ban on entering the park. We sought to assess the effectiveness of these control measures. Methodology/Principal findings We used a mathematical model to describe the transmission dynamics. Using dates of exposure and illness onset, we categorized cases into three groups according to the availability of these datasets. The infection process was parametrically modeled by generation, and convolution of the infection process and the incubation period was fitted to the data. By estimating the effective reproduction number, we determined that the effect of dengue risk communication together with mosquito control from 28 August 2014 was insufficiently large to lower the reproduction number to below 1. However, once Yoyogi Park was closed on 4 September, the value of the effective reproduction number began to fall below 1, and the associated relative reduction in the effective reproduction number was estimated to be 20%–60%. The mean incubation period was an estimated 5.8 days. Conclusions/Significance Regardless of the assumed number of generations of cases, the combined effect of mosquito control, risk communication, and park closure appeared to be successful in interrupting the chain of dengue transmission in Tokyo.

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Section: Introductionmentioning

confidence: 99%

Assessing dengue control in Tokyo, 2014

2019

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“…albopictus has also been associated with local arboviral transmission and disease outbreaks, specifically in temperate regions where Ae. aegypti is absent or uncommon[ 12 – 17 ]. However, Ae .…”

Section: Introductionmentioning

confidence: 99%

Defining the Risk of Zika and Chikungunya Virus Transmission in Human Population Centers of the Eastern United States

et al. 2017

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The recent spread of mosquito-transmitted viruses and associated disease to the Americas motivates a new, data-driven evaluation of risk in temperate population centers. Temperate regions are generally expected to pose low risk for significant mosquito-borne disease; however, the spread of the Asian tiger mosquito (Aedes albopictus) across densely populated urban areas has established a new landscape of risk. We use a model informed by field data to assess the conditions likely to facilitate local transmission of chikungunya and Zika viruses from an infected traveler to Ae. albopictus and then to other humans in USA cities with variable human densities and seasonality. Mosquito-borne disease occurs when specific combinations of conditions maximize virus-to-mosquito and mosquito-to-human contact rates. We develop a mathematical model that captures the epidemiology and is informed by current data on vector ecology from urban sites. The model demonstrates that under specific but realistic conditions, fifty-percent of introductions by infectious travelers to a high human, high mosquito density city could initiate local transmission and 10% of the introductions could result in 100 or more people infected. Despite the propensity for Ae. albopictus to bite non-human vertebrates, we also demonstrate that local virus transmission and human outbreaks may occur when vectors feed from humans even just 40% of the time. Inclusion of human behavioral changes and mitigations were not incorporated into the models and would likely reduce predicted infections. This work demonstrates how a conditional series of non-average events can result in local arbovirus transmission and outbreaks of human disease, even in temperate cities.

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“…in response to an outbreak), trap location and trap type. 53–57 , 73 , 81–83 Data on vector density at a higher spatial resolution using standardised methodology would provide a more comprehensive analysis. Alternatively, Massad et al .…”

Section: Discussionmentioning

confidence: 99%

Yellow fever in Asia–a risk analysis

Daniels

Gaythorpe

Imai

et al. 2021

Journal of Travel Medicine

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Background There is concern about the risk of yellow fever (YF) establishment in Asia, owing to rising numbers of urban outbreaks in endemic countries and globalisation. Following an outbreak in Angola in 2016, YF cases were introduced into China. Prior to this, YF had never been recorded in Asia, despite climatic suitability and the presence of mosquitoes. An outbreak in Asia could result in widespread fatalities and huge economic impact. Therefore, quantifying the potential risk of YF outbreaks in Asia is a public health priority. Methods Using international flight data and YF incidence estimates from 2016, we quantified the risk of YF introduction via air travel into Asia. In locations with evidence of a competent mosquito population, the potential for autochthonous YF transmission was estimated using a temperature-dependent model of the reproduction number and a branching process model assuming a negative binomial distribution. Results 25 cities across Asia were estimated to be at risk of receiving at least one YF viraemic traveller during 2016. At their average temperatures, we estimated the probability of autochthonous transmission to be below 50% in all cities, which was primarily due to the limited number of estimated introductions that year. Conclusion Despite the rise in air travel, we found low support for travel patterns between YF endemic countries and Asia resulting in autochthonous transmission during 2016. This supports the historic absence of YF in Asia and suggests it could be due to a limited number of introductions in previous years. Future increases in travel volumes or YF incidence can increase the number of introductions and the risk of autochthonous transmission. Given the high proportion of asymptomatic or mild infections and the challenges of YF surveillance, our model can be used to estimate the introduction and outbreak risk, and can provide useful information to surveillance systems.

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Estimation of reproduction number and probable vector density of the first autochthonous dengue outbreak in Japan in the last 70 years

Cited by 9 publications

References 17 publications

Assessing dengue control in Tokyo, 2014

Assessing dengue control in Tokyo, 2014

Defining the Risk of Zika and Chikungunya Virus Transmission in Human Population Centers of the Eastern United States

Yellow fever in Asia–a risk analysis

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