Epidemiology of influenza patients in Thailand between A.D. 2014 – 2021

Abstract

In Thailand, Influenza cases are reported in all age groups and distributed in all parts of the country. The epidemiological characteristics of influenza patients are crucial, which can be utilized for disease surveillance, guideline setting, and planning for disease prevention and control measures. This study aimed to describe the epidemiological characteristics of influenza patients in Thailand during A.D. 2014 – 2021. This was a descriptive study using secondary data from the National Disease Notification Surveillance (Report 506), and laboratory confirmed Influenza virus data from the Department of Disease Control, Ministry of Public Health. This study revealed a total of 1,236,299 influenza patients in Thailand during A.D. 2014 – 2021. There were 296 deaths among those influenza cases with the case fatality rate accounting for 0.02%. Male to female ratio was 1:1.03. Most patients were found among children less than 5 years of age accounting for 21.26%, followed by more than 5 to 9 years of age which accounting for 18.91%. The highest morbidity was found in 2019 accounting for 606.00 per 100,000 population (396,363 cases), and the highest case fatality rate was found in 2014, accounting for 0.12% (91 cases). The Influenza morbidity rate was considerably decreased during the Coronavirus 2019 pandemic years. Regarding spatial distribution, the highest morbidity rate was found in the central region. Influenza cases were reported from the top 5 provinces which were mostly shown in Bangkok, followed by Rayong, Chiang Mai, Phayao, and Chanthaburi respectively. From year 2016 to 2019, most cases were found in September every year. The predominant influenza virus strains were various annually. This study shows that the number of cases was diversely reported by age groups, regions, and seasonal intervals. This study recommends influenza surveillance system should focus on school children specifically from newborn to under 9 years of age as most reported cases were found.  Active surveillance can be initiated and focused on the area of the most populated provinces including the center of the economy such as Bangkok, Rayong and Chiang Mai, which specific measures, guidelines, and surveillance can be implemented. Moreover, early influenza detection should be provided before the rainy season in September when most cases are found annually. Consequently, effective control measures for influenza cases can be performed which results in reducing the morbidity rates, and case fatality rates of influenza patients.