Version: April 2024
Japanese encephalitis (JE) is a mosquito-borne viral disease endemic to parts of Asia and the Pacific. Transmission primarily occurs in rural agricultural regions where flooding irrigation is used. The JE virus can cause inflammation of the brain leading to high fever, disorientation, coma, seizures, and even death. Vaccines are available for protection against JE, but no specific antiviral treatments exist. Human cases can be reduced by controlling mosquito populations and avoiding bites. JE is a major cause of viral encephalitis in Asia with thousands of cases reported annually.
A pattern of seasonal fluctuation is apparent in Japanese Encephalitis cases in the Chinese mainland from 2014 to 2024. The highest incidence typically occurs in the summer months, particularly from July to September, which is the season for the carrier mosquito’s activity. A case peak was observed in August 2018 with 904 cases, the highest compared to any other month. Conversely, winter months tend to have the lowest incidence, correlating with lower mosquito activity. Over the years, overall cases seem to have slightly decreased, with 41 cases in April 2014 and only 1 case in April 2024.
Similar to the cases, the deaths from Japanese Encephalitis tend to peak in the summer months. The highest number of deaths occurred in August 2018 with 55 fatalities. However, there have been exceptions, like April 2019, which saw 26 deaths, significantly higher than ordinary spring months. The death count has generally decreased over the years, showing vector control efforts or healthcare management improvements. The last recorded death was in February 2024, and a declining trend of fatalities is noticeable in recent years.