Liúxíngbìngxué yánjiū jíbìng zài rénqún zhōng de fēnbù.
Epidemiology studies the distribution of disease in populations.
Tips
memory
Parse as 流行病 (epidemic) + 学 (study), literally 'study of spreading-sickness.' 流行 alone means 'popular / in fashion,' so 流行歌曲 is 'pop songs', same 'widely spread' sense.
