To estimate the time-dependent transmission potential of primary pneumonic plague (PPP), we analyzed historical records from six outbreaks. Based on contact investigation information (source of infection information) of three outbreaks, we generalized the probability density function of the serial interval with a Gamma distribution using maximum likelihood estimations. Furthermore, we used a likelihood-based approach to estimate effective reproduction numbers at time t, R_t, incorporating records from the remaining three outbreaks by assuming independence within unknown contact networks. According to our estimates, the R_t of PPP during the initial phases of each epidemic were roughly in the order of 1.3 (95% confidence interval (CI): 0.0-4.3) in Oakland, 1.4 (0.0-4.6) in Rangoon and 6.5 (0.0-16.0) in Ecuador. The expected values of R_t were shown to slightly exceed unity, even in latter stages. While declining trends in R_t were observed in Oakland and Ecuador, no such trend was observed in Rangoon. The findings suggest that the three outbreaks investigated could have been accompanied by demographic stochasticity. The statistical usefulness of the transformation procedure, even with a small number of recorded cases available, was demonstrated, and the expected responses to bioterrorism using Yersinia pestis were discussed.

OBJECTIVES: Although the role of specific holidays in modifying transmission dynamics of infectious diseases has received some research attention, the epidemiological impact of public holidays on the transmission of coronavirus disease 2019 (COVID-19) remains unclear. METHODS: To assess the extent of increased transmission frequency during public holidays, we collected COVID-19 incidence and mobility data in Hokkaido, Tokyo, Aichi, and Osaka from February 15, 2020 to September 30, 2021. Models linking the estimated effective reproduction number (Rt) with raw or adjusted mobility, public holidays, and the state of emergency declaration were developed. The best-fit model included public holidays as an essential input variable, and was used to calculate counterfactuals of Rt in the absence of holidays. RESULTS: During public holidays, on average, Rt increased by 5.71%, 3.19%, 4.84%, and 24.82% in Hokkaido, Tokyo, Aichi, and Osaka, respectively, resulting in a total increase of 580 (95% confidence interval [CI], 213 to 954), 2,209 (95% CI, 1,230 to 3,201), 1,086 (95% CI, 478 to 1,686), and 5,211 (95% CI, 4,554 to 5,867) cases that were attributable to the impact of public holidays. CONCLUSIONS Public holidays intensified the transmission of COVID-19, highlighting the importance of considering public holidays in designing appropriate public health and social measures in the future.

Objective: To investigate a measles outbreak that spread to Japan and Taiwan, China during March–May 2018, exploring the characteristics of the super-spreading event. Methods: A contact investigation of the index case and reconstruction of the epidemiological dynamics of measles transmission were conducted. Employing a mathematical model, the effective reproduction number was estimated for each generation of cases. Results and discussion A single index case gave rise to a total of 38 secondary cases, 33 in Japan and five in Taiwan, China. Subsequent chains of transmission were observed in highly vaccinated populations in both Japan and Taiwan, China. The effective reproduction number of the second generation was >1 for both Japan and Taiwan, China. In Japan, the reproduction number was estimated to be <1 during the third generation. Vaccination of susceptible individuals is essential to prevent secondary and tertiary transmission events.