Analysis of Influenza Cases and Seasonal Index in Thailand

Abstract

This study investigated the pattern and seasonal index of influenza cases in Thailand. Our results showed that southern Thailand had the highest influenza incidence among the four regions of Thailand (i.e. north, northeast, central and southern Thailand). The influenza pattern in southern Thailand was similar to that of north- eastern Thailand. Seasonal index values of influenza cases in Thailand were higher in the hot season than in the wet season. Influenza cases started to increase at the beginning of the hot season (April), reached a maximum in August, rapidly declined in the middle of the wet season and reached the lowest value in December. Seasonal index values for northern Thailand differed from other regions of Thailand. region of Thailand. The major influences on Thailand's climate are its location in the tropical monsoon zone of mainland Southeast Asia and certain topographic features that affect the distribution of precipitation. Beginning in May, the warm, humid air masses of the southwest monsoon flow northeastward over the region from the Indian Ocean, depositing great quantities of precipitation; rainfall reaches a maximum in September. The wind pattern is reversed between November and February, when the northeast monsoon brings cool, relatively dry air masses in a southwesterly flow to create a seasonably cooler climate for much of the country. Stagnant air in March and April is associated with a distinct hot and dry inter-monsoonal period (4).