3
A case control study ( 1 : 2 ) of 182 pairs of Hepatitis A was carried out in Weng - ling Zhe - jiang during April 1988 .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 None