Epidemiological Features, Clinical Symptoms and Environmental Risk Factors for Notifiable Japanese Encephalitis in Taiwan from 2008 to 2020 (Preprint)

Abstract

Japanese encephalitis is a zoonotic parasitic disease caused by the Japanese encephalitis virus, and may cause fever, nausea, headache, or meningitis. This study aimed to investigate the epidemiological features, epidemic trends, and correlations between the number of confirmed Japanese encephalitis cases in Taiwan from 2008 to 2020 in gender, age, season, and residential area; clinical symptoms of cases, high-risk areas of disease and hypothesized the environmental and climate factors also might affect the disease in Taiwan.

This study aims to comprehensively investigate the epidemiological, clinical, and environmental characteristics of Japanese Encephalitis (JE) in Taiwan using population surveillance data gathered over a 13-year period.

This study reviewed publicly available annual summary data on reported Japanese encephalitis cases in the Taiwan Centers for Diseases Control (TCDC) between 2008 and 2020.

This study collected 309 confirmed domestic and four patients with imported Japanese encephalitis. There was an increasing trend in the incidence of Japanese encephalitis, 0.69–1.57 cases per 1,000,000 people, peaking in 2018. Case fatality rate is 8.3%. Comparing sex, age, season, and place of residence, the incidence rate was highest in male, 40–59 years-old patients, summer, and the Eastern region, with 1.89, 3.27, 1.25, and 12.2 cases per million population, respectively. The average coverage rate of Japanese encephalitis vaccine for children in Taiwan is 94.9%. Additionally, the major clinical manifestations of the case include fever, unconsciousness, headache, stiff necks, psychological symptoms, vomiting, and meningitis. The major occurrence place of Japanese encephalitis included paddy fields, pig farms, pigeon farms, poultry farms, and pond. For air pollution factors, linear regression analysis showed that SO2 (ppb) concentration was positively associated with Japanese encephalitis cases (β = 2.184, p = 0.020), but CO (ppb) concentration was negatively (β = -0.157, p = 0.014). For climate factors, relative humidity (%) was positively associated with Japanese encephalitis cases (β = 0.380, p = 0.021).

This study is the first to report confirmed cases of Japanese encephalitis from the surveillance data of the TCDC between 2008 and 2020. It identified that residence, season, and age were risk factors for Japanese encephalitis in Taiwan. Air pollution and climatic factors indeed influence the rise in Japanese encephalitis cases. This study confirmed that Japanese encephalitis remains a prevalent infectious disease in Taiwan, with its epidemic gradually increasing in severity. These findings empower clinicians and healthcare providers to make informed decisions, guiding their care and resource allocation for patients with Japanese encephalitis, a disease that significantly impacts the health and well-being of the Taiwanese population.