The multiple regression was based on the formula: Y = α +β1X1 +β2X2 +…+βkXk +ε, where Y was the DHF patients in household, β1 to k were the regression coefficient of household’s activities variables of X1 to k and ε was the error term. In the multiple regression analysis, the fifteen variables that were significantly correlated to DHF patients (see Table 1 for more details) were included in the tentative model.