Assessing dengue control in Tokyo, 2014

Abstract

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.

Initial Cluster of Novel Coronavirus (2019-nCoV) Infections in Wuhan, China Is Consistent with Substantial Human-to-Human Transmission

“…The number of cases in each generation is therefore 1, 3, 4, 27, and 6 cases, respectively. These numbers allow for the estimation of generation-dependent reproduction numbers-the average number of secondary cases per primary case for each generation [5] ( Figure 1B). Assuming that the offspring distribution is Poisson distributed, the reproduction numbers can be estimated at 3.0 (95% confidence interval (CI): 0.75, 7.8), 1.3 (95% CI: 0.4, 3.1), 6.7 (95% CI: 4.5, 9.6), and 0.2 (95% CI: 0.1, 0.5)-broadly in line with preliminary basic reproduction number estimates of 1.5-3.5 quoted by the WHO and presented elsewhere [6,7].…”

Transmission Network of Measles During the Yamagata Outbreak in Japan, 2017

“…Using the illness onset date along with the serial interval, and also analyzing the geographic location for an exposure, a transmission network with 19 unknown links was reconstructed. 37,45,49 Comparing AIC values between Models 1 and 2 for the incidence dataset, Model 1 yielded a smaller AIC value than that of Model 2 (403.3 vs. 442.5 for Models 1 and 2, respectively) and was regarded as better fitted to the observed data. In In addition to these practical findings, it should be noted that we were able to clarify the difference in retrievable information between using temporal data alone and using network data, as an important technical take-home message.…”

“…serial interval between the primary case v(i) and the secondary case i is expressed as titv(i). The serial interval distribution for other infectious diseases (e.g., plague and foot and mouth disease 40,45 ) have been empirically fitted to the gamma distribution; for example, Klinkenberg and Nishiura have used the gamma distribution for the generation time of measles 46 . Similarly, the serial distribution g(.)…”

Reconstruction and analysis of the transmission network of African swine fever in People’s Republic of China, August 2018–September 2019

“…Data were aggregated into weekly counts of infected units { 8 ; = 1,2, … } with the first week set to the date of start of the index outbreak. The force of infection 8 was modelled using a sequential generation process referred to as a generation-dependent model (Akhmetzhanov et al, 2018;Yuan et al, 2019). An infected unit generates new secondary infections based on the probability density function of the generation time 8 ( 0 ).…”